+++ /dev/null
-NEWS
-====
-
-------------------------------------------
-current master branch "cascading gradient"
-------------------------------------------
-
- - para_afh learned to modify meta tags of mp3 wma ogg spx
- opus flac aac files.
- - afs commands propagate error codes to the client.
- - The check command now also checks the attribute table for
- inconsistencies.
- - New -v flag for the version command (print verbose version string)
- - New option --priority for para_server and para_audiod.
-
-
---------------------------------------
-0.5.5 (2015-09-20) "magnetic momentum"
---------------------------------------
-
-Many new features and a lot of other improvements.
-
- - On Linux systems, local sockets are now created in the
- abstract name space by default. This allows to get rid of
- the socket specials in /var/paraslash.
- - The --user-allow option of para_audiod now accepts also
- usernames rather than only user IDs.
- - New autoconf macros to avoid duplication in configure.ac.
- - Status items (as shown by para_gui) are updated correctly
- when the meta information of the current audio changes.
- - para_server and para_audiod no longer refuse to start in
- the background if no log file is given. Instead, all log
- messages go to /dev/null in this case.
- - Web page cleanup.
- - New syntax for the -l and -s options of the ls command.
- These options should now be specified as -l=v rather than
- -lv, for example. The old syntax still works, but support
- will be dropped in v0.6.0.
-
-Download: ./releases/paraslash-0.5.5.tar.bz2 (tarball)
-./releases/paraslash-0.5.5.tar.bz2.asc (signature)
-
-------------------------------------------
-0.5.4 (2015-01-23) "exponential alignment"
-------------------------------------------
-
-Another cleanup and bugfix release.
-
- - New server command: tasks.
- - Minor cleanups to daemon.c.
- - New URLs for home page and git services.
- - Improved error diagnostics for the mvblob commands.
- - New sender subcommand: status.
- - Improved help text for server and afs commands.
- - audiod memory leak fixes.
- - Miscellaneous improvements to the build system.
- - oss_writer improvements.
- - Improved handling of mp3 files with both id3v1 and id3v2 tags.
-
-Downloads: ./releases/paraslash-0.5.4.tar.bz2 (tarball)
-./releases/paraslash-0.5.4.tar.bz2.asc (signature)
-
----------------------------------------------
-0.5.3 (2014-08-01) "symbolic synchronization"
----------------------------------------------
-
-Not many new features, but lots of fixes and usability improvements.
-
- - para_gui has been converted to use the paraslash scheduler.
- - Various alsa-related fixes, mostly for the raspberry pi.
- - Many scheduler improvements and cleanups.
- - The test suite has been extended to include sanity checks
- for the generated man pages.
- - ao_writer fixes. This writer was in a quite bad shape. Many
- serious bugs have been fixed.
- - new audiod command: version.
- - Minor improvements to the bitstream API.
- - The cpsi command now prints a meaningful error message if
- none of the given patterns matched any audio file.
-
-Downloads: ./releases/paraslash-0.5.3.tar.bz2 (tarball),
-./releases/paraslash-0.5.3.tar.bz2.asc (signature)
-
-----------------------------------------
-0.5.2 (2014-04-11) "orthogonal interior"
-----------------------------------------
-
-The new sync filter, the AES_CTR128 stream cipher and the overhauled
-network code are the highlights of this release. It also includes a
-fair number of smaller fixes and improvements not mentioned here.
-
- - The new sync filter synchronizes playback between multiple
- clients.
- - Connections between para_server and para_client are now
- encrypted by means of AES rather than RC4 if both sides
- support it. RC4 is still available as a fallback. This
- feature is fully transparent, i.e. no command line options
- are necessary, and a client linked against openssl can
- speak with a server linked against libgcrypt and vice versa.
- - Major cleanup of the networking subsystem.
- - Improvements to para_fade: the new set mode, multi-channel
- initial volumes, better error logging.
- - The man pages of para_audiod, para_filter, para_recv, and
- para_write contain the relevant options for receivers, filters,
- writers. This broke in 0.5.0.
- - ogg/vorbis latency improvements.
- - Improved user manual.
- - Minor fixes to avoid clang warnings.
-
-Downloads: ./releases/paraslash-0.5.2.tar.bz2 (tarball),
-./releases/paraslash-0.5.2.tar.bz2.asc (signature)
-
-------------------------------------------
-0.5.1 (2013-12-20) "temporary implication"
-------------------------------------------
-
-Lots of fixes and improvements all over the place, and a major overhaul
-of the build system.
-
- - Audiod improvements and fixes.
- - Buffer tree robustness improvements.
- - Cleanup of the mood subsystem.
- - Fixes and cleanups for the flac decoder.
- - Latency improvements for the ogg/opus decoder.
- - Crypto support is now optional. On systems without
- openssl/gcrypt, the build succeeds but para_server,
- para_audiod, para_client won't be built.
- - The build system now works for cross-compile setups.
- - The dependency tree has been flattened, which speeds up
- builds and avoids to recreate the man pages on every change.
- - The error code helper has been rewritten from perl to C,
- which further improves build time.
- - Many small bugs in the build system have been identified
- and fixed.
-
-Downloads: ./releases/paraslash-0.5.1.tar.bz2 (tarball),
-./releases/paraslash-0.5.1.tar.bz2.asc (signature)
-
-----------------------------------------
-0.5.0 (2013-08-23) "invertible validity"
-----------------------------------------
-
-Some API-breaking changes, one serious bug fix, and a lot of bike-shedding.
-
- - The sideband compatibility code has been removed, hence
- sideband connections (introduced in 0.4.11) are now mandatory.
- - Addblob commands can produce output.
- - The stat command no longer sends garbage when para_server was
- compiled against libgcrypt.
- - Dependencies for gengetopt files are computed automatically.
- This eliminates a constant source of build bugs.
- - The setatt command now accepts file name patterns rather than only
- path names.
- - overview.pdf is now based on dia, a simple diagram creation program.
- The new version is much more detailed and contains descriptions of
- the various programs of the paraslash package.
- - The separator of all multi-word options has been changed from
- underscore to dash. For example --log_color becomes --log-color.
- - Overhauled web pages and the new logo.
-
-Downloads: ./releases/paraslash-0.5.0.tar.bz2 (tarball),
-./releases/paraslash-0.5.0.tar.bz2.asc (signature)
-
---------------------------------------
-0.4.13 (2013-07-29) "spectral gravity"
---------------------------------------
-
-One more 0.4.x release before the API-breaking changes for 0.5.0 go
-in. The main features of this release are the ogg/opus audio format,
-and UTF-8 support, but it includes also tons of other improvements
-and fixes all over the place.
-
- - New audio format: ogg/opus.
- - UTF8 support for para_gui and the mp3 audio format handler.
- - Scheduler improvements and fixes.
- - The obsolete gettimeofday() function has been replaced
- by clock_gettime() on systems which support it.
- - Speed and usability improvements for para_gui.
- - para_client now restores the fd flags of stdin and stdout
- on shutdown.
- - Improved manual pages.
- - Consistent version strings for all executables.
- - Reduced dependencies on generated files result in fewer
- recompilations on changes.
- - Performance improvements for the compress filter.
- - Improved downloads web page.
-
------------------------------------------
-0.4.12 (2012-12-20) "volatile relativity"
------------------------------------------
-The new command line player, the resample filter, ALSA support for
-para_fade, and the improved build system are the highlights of this
-release which probably marks the end of the 0.4.x series.
-
- - The afh receiver and the para_play executable.
- - The resample filter: A sample rate converter based on
- libsamplerate.
- - The "versions" directory has been removed from the master
- branch. The tarballs of the old releases are now available
- in the new "releases" branch.
- - Overhaul of the build system: All generated files are now
- written to the "build" directory.
- - The modular mixer API and the alsa mixer.
- - Minor fixes for the osx writer.
-
---------------------------------------
-0.4.11 (2012-07-20) "mutual diversity"
---------------------------------------
-
-The major feature in this release is the new sideband API for
-client-server communication. This API will be used exclusively starting
-with 0.5.0, which breaks backward compatibility but allows to get rid
-of quite some compatibility code. Other noteworthy changes include
-decoder latency improvements and a long-standing bug fix for the
-ALSA writer.
-
- - Sideband connections: If both para_server and para_client
- support this feature, data is sent as a multiplexed stream.
- - The --no_default_filters option of para_filter has been
- removed.
- - Several fixes and latency improvements to various decoders.
- - The ALSA writer now limits the prebuffer time to 500ms.
- - Documentation improvements.
- - Overhaul of the command_util.sh script.
- - Fixes for some minor problems found by the clang analyzer.
- - Compiles (almost) without warnings on gcc-3.
- - Robustness improvements of the buffer tree code.
-
-------------------------------------------
-0.4.10 (2012-03-30) "heterogeneous vacuum"
-------------------------------------------
-
-Nothing earth-shaking in this release, but quite a few usability
-improvements and the usual mix of cleanups and fixes.
-
- - The --no_default_filters option of para_filter has been
- deprecated. It still works but has no effect and will be
- removed in the next version.
- - para_gui now prints also the stderr output of the executing
- command in the bottom window.
- - Cleanup and consolidation of the various wrappers for
- write(), writev(), send() and friends.
- - The obscure error messages on mmap() failures have been
- replaced by meaningful messages. This affects mainly
- para_afh.
- - para_audioc: Cleanups and memory leak fixes.
- - Test 0004-server no longer fails if para_server is not
- being built.
- - New configure options: --with-id3tag-{headers,libs}.
-
--------------------------------------
-0.4.9 (2011-12-06) "hybrid causality"
--------------------------------------
-
-Support for another audio format, interactive mode for para_client
-and para_audiod and many small improvements/fixes all over the place.
-
- - Support for flac, the free lossless audio codec.
- - Fix for an endless loop in the mp3 decoder for certain
- (corrupt) mp3 files.
- - When executed without specifying a command, para_client
- and para_audioc start an interactive shell (requires
- libreadline being installed). The interactive mode offers
- full tab completion and command line history.
- - autogen.sh now detects a distcc setup and adjusts the
- parameter for the -j option of make accordingly.
- - Shared memory areas are no longer restricted to 64K. We now
- detect the maximal size of a shared memory area at runtime.
- - cleanup of the internal uptime API.
- - para_server prefaults the mmapped audio file to avoid
- delays on slow media.
- - A new test for the test-suite that exercises the
- communication between para_server and para_audiod.
- - The alsa writer eats up less CPU cycles when configured to
- use the DMIX plugin.
- - Simplified and unified receiver code.
- - Makefile cleanups.
- - Commands which print a list of matching audio files now
- emit a meaningful error message if no audio file matched the
- given pattern(s).
-
---------------------------------------
-0.4.8 (2011-08-19) "nested assignment"
---------------------------------------
-
-Gcrypt support, the overhauled osx writer and regex format specifiers
-are the highlights of this release.
-
- - support for libgcrypt as a drop-in replacement for openssl.
- Run configure --enable-cryptolib=gcrypt to link against
- libgcrypt. The two crypto implementations are compatible to
- each other, i.e. a para_client executable linked against
- gcrypt can connect to para_server linked against libssl
- and vice versa.
- - Rewrite of the osx writer (output plugin for Mac OS).
- - audiod: The format specifier for receivers, filters and
- writers is now treated as a regular expression. This allows
- to replace 5 lines in the config file (one for each audio
- format) by one single line. See the manual for details.
- - The *.cmdline.[ch] files are no longer contained in the released
- tarballs. This reduces the size of the tarballs but requires
- gengetopt to build the tarball.
- - Compiles cleanly also with llvm/clang.
- - Corrupt mp3 files are handled more gracefully.
- - The alsa writer uses poll fds instead of computing timeouts.
- - Cleanup of the generic writer API.
- - sched: Optimized zero timeouts.
- - vss timeout cleanups.
- - oggdec fixes and improvements.
-
---------------------------------------
-0.4.7 (2011-06-01) "infinite rollback"
---------------------------------------
-
-The new ao writer, support for ssh RSA keys and a couple of other
-enhancements.
-
- - Support for ESD, Pulseaudio, AIX, Solaris, IRIX and other
- platforms through the libao audio library.
- - Support for RSA keys generated with ssh-keygen.
- - configure: improved options for ogg/vorbis/speex.
- - The git version reported by --version always matches HEAD.
- - The autogen script detects the number of processors and
- runs a parallel make if possible.
- - Major cleanup of the crypto API.
- - Documentation updates.
-
-------------------------------------------
-0.4.6 (2011-03-31) "deterministic entropy"
-------------------------------------------
-
-Lots of ogg/vorbis improvements, the new test suite, enhancements
-for para_gui and a fair amount of other bug fixes.
-
- - For DCCP/OGG streams the audio file header is only sent once
- at the beginning of the stream rather than periodically
- every five seconds. This reduces network traffic and the
- FEC group size.
- - The vorbis comment header is replaced by an empty dummy header
- before the header is sent over the network. This also results in
- less network traffic and smaller FEC groups.
- - The new "test" make target allows to perform some sanity checks prior
- to installing the package.
- - ogg timing fixes and performance improvements
- - Scheduler improvements
- - Proper exit codes for para_write
- - para_gui: New option --theme to select a startup theme. Several
- other improvements and fixes.
- - aacdec error message cleanups
- - simplified color error handling
-
---------------------------------------------
-0.4.5 (2010-12-17) "symmetric randomization"
---------------------------------------------
-
-Bug fixes, internal cleanups and variable-sized FEC slices.
-
- - Contains a fix for an invalid-free-bug in the ogg audio format
- handler code.
- - Switching off the DCCP sender works again.
- - para_audiod handles crashes of para_server more robustly.
- - Internal scheduler and writer cleanups.
- - Reduced latency due to variable-sized FEC slices.
- - Improved documentation and error diagnostics.
- - The build of para_server is now optional, allowing the build
- to succeed in case libosl is not installed.
-
-------------------------------------------
-0.4.4 (2010-08-06) "persistent regularity"
-------------------------------------------
-
-Support for yet another audio format, para_write improvements and
-bug fixes.
-
- - Support for the speex codec.
- - Support for sample formats other than 16 bit little endian.
- - error2.h is now created by a perl script which speeds up configure
- considerably.
- - Fix a bug in the aac decoder which could lead to segfaults in
- para_filter/para_audiod.
- - Fixes for autoconf-2.66.
-
-----------------------------------------
-0.4.3 (2010-07-05) "imaginary radiation"
-----------------------------------------
-
-Many improvements for the DCCP and the UDP transport, the new user
-manual and the usual mix of bug fixes and internal improvements.
-
- - FEC support for the DCCP sender (Gerrit Renker). The new
- --dccp_max_slice_size, --dccp_data_slices_per_group and
- --dccp_slices_per_group options can be used to set the FEC
- parameters for the DCCP transport.
- - DNS lookups for UDP targets (Gerrit Renker).
- - The new user manual replaces the README, README.afs, REQUIREMENTS
- and INSTALL documents.
- - Fix an end-of-file detection bug in the oggdec filter.
- - The new nonblock API.
- - Both options of the oggdec filter have been removed.
- - New debug mode for the internal scheduler.
-
-------------------------------------------
-0.4.2 (2010-04-23) "associative expansion"
-------------------------------------------
-
-It's been some time since the last release, but finally here is
-paraslash-0.4.2. The bulk of the changes comes from the new buffer
-tree API, but there are changes all over the tree. Mainly performance
-and usability improvements, but also quite some bug fixes.
-
- - The new buffer tree API.
- - DCCP: Support for CCID negotiation (Gerrit Renker).
- - UDP robustness fixes.
- - The --bufsize option for mp3dec is gone as it no longer makes sense
- for the new buffer tree API.
- - Fix audible buffer underruns for wma streams.
- - The alsa writer no longer prints meaningless underrun durations.
- - audiod: Defaults work also for udp streams. If no filter is
- given for an audio format that is received via upd, fecdec is
- automatically added as the first filter (along with the decoder).
-
----------------------------------------
-0.4.1 (2009-12-22) "concurrent horizon"
----------------------------------------
-
-Support for another audio format, minor feature enhancements and lots of bug
-fixes. All fixes that have been accumulated in the maint branch (in particular
-those mentionened in the 0.3.6 release notes) appear in this release as well.
-
- - wma support.
- - new afh option: --human to activate human-readable output.
- - new server/audiod option: --log-timing to print timing information.
- - build system improvements.
- - source code documentation updates.
-
--------------------------------------
-0.3.6 (2009-12-07) "cubic continuity"
--------------------------------------
-
-Quite a few bugs have been found and fixed since 0.3.5, so here's
-another 0.3.x release. No new features.
-
- - Always check return value of malloc().
- - ogg vorbis/FEC: Do not write garbage after the audio file header.
- - exit if root privileges could not be dropped.
- - FEC: Fix computation of extra slices.
- - oss: Fix check for empty input buffer.
- - Avoid buffer underruns due to filter chain output buffer constraints.
- - server: Fix assignment of afs_pid.
- - Don't panic if the afs database contains unknown audio formats.
- - http/dccp: Do not send the audio file header twice.
- - FEC: Timing improvements.
-
-----------------------------------------------
-0.4.0 (2009-11-10) "simultaneous independence"
-----------------------------------------------
-
-Two significant changes which require the new version number: The
-improved authentication dialog and the fact that the database code
-has been moved to a library, libosl. To use the new version, you have
-to generate new RSA keys, see INSTALL for details. A shell script is
-provided for conversion of the 0.3 database to the new 0.4 format.
-
- - stronger crypto for client authentication
- - the database code has been moved to a library
- - improved status item handling
- - cleanup of the build system
- - The "-V" option now also prints the git version
- - the new parser-friendly listing mode for the ls and stat commands
- - mandatory rc4 encryption
- - major audio format handler cleanups
- - (id3,...) tags are no longer stored as a combined string in the database
- - new mood methods: artist_matches, title_matches, comment_matches,
- album_matches, year_maches, year.
-
---------------------------------------------
-0.3.5 (2009-09-21) "symplectic separability"
---------------------------------------------
-
-Full client support for *BSD Unixes, complete re-write of the ogg
-vorbis audio format handler, various improvements all over the place
-and the usual mix of bugfixes. This release marks the end of the 0.3
-series if no serious problems show up.
-
- - the new oss writer (supported on *BSD and Linux)
- - rewrite of the ogg vorbis audio format handler. It's
- recommended to replace the chunk tables of existing ogg
- vorbis files in the afs database by re-adding these files
- with "add -f".
- - support for netmask subsets (Gerrit Renker)
- - the new prebuffer filter
- - improved signal handling
- - variable fec output buffer size
- - improved FEC timing fixes audible buffer underruns in UDP mode
- - --log_color actually works
- - new ls option: -d (print dates as seconds after the epoch)
- - update to gengetopt 2.22.2
- - support for RSA keys of size > 512 bits
- - new option "mixer_channel" for para_fade
-
------------------------------------------
-0.3.4 (2009-05-07) "elliptic inheritance"
------------------------------------------
-
-The new udp sender, forward error correction, colored logs and various
-other improvements. As the udp sender does not depend on any special
-libraries, it is built unconditionally.
-
- - The udp sender replaces the ortp sender. The new code uses forward
- error correction to protect against packet losses. Many thanks to
- Gerrit Renker for providing ipv6 support.
- - The default port for udp streaming now defaults to 8000, like
- for the http and the dccp senders/receivers.
- - Loglevels are now specified as symbolic names, e.g.
- "--loglevel info".
- - improved ipv4 and ipv6 URI parser (Gerrit Renker).
- - para_server/para_audiod: Color support for log messages.
- - new options for mp3dec: --ignore-crc, --bufsize
- - new audiod option: --config-file.
- - gengetopt cleanups.
- - Improved help/man pages: The documentation of para_audiod,
- para_recv, para_filter and para_write now also contains
- all options of the available receivers/filters/writers. The
- man page of para_fade contains a description of the different
- modes of operation.
- - More source code documentation.
- - vss timing fixes.
-
---------------------------------------------
-0.3.3 (2008-12-01) "axiomatic perspectivity"
---------------------------------------------
-
-Internal code cleanups, bug fixes, improved tag handling and the new
-amplification filter.
-
- - para_server uses the generic scheduling code.
- - overhaul of the virtual streaming system.
- - mp3: id3 version 2 support via libid3tag (optional)
- - ogg: vorbis comment support.
- - aac meta info support.
- - mp3 audio format handler cleanups.
- - new filter: "amp" to amplify the amplitude of the audio stream
- - new status item/database entry: amplification. It is
- used by the amp filter to pre-amplify the audio stream.
- - fix a close-without-open bug in para_write.
- - fix a bug in com_init() which was introduced in 0.3.2.
- - better error diagnostics for para_client.
-
------------------------------------------
-0.3.2 (2008-04-11) "probabilistic parity"
------------------------------------------
-
-The new para_afh executable, scheduling and documentation improvements.
-
- - new ls option: -lc (list chunk table)
- - new executable: para_afh, the stand-alone audio file handler tool
- - afs commands can send output more than SHMMAX (32MB on Linux). This
- also reduces the memory usage of commands that produce large amounts
- of output.
- - major scheduler and audiod cleanups.
- - more detailed and much nicer man pages.
-
----------------------------------------
-0.3.1 (2008-02-23) "liquid interaction"
----------------------------------------
-
-A mix of cleanups, bug fixes, improvements, and some new features. No
-significant changes to the new database (osl) code, which is generally
-a good sign.
-
- - Share some similar/duplicate code between the http and the
- dccp sender.
- - Generic access control lists for paraslash senders.
- - dccp sender: Access control lists, connection limiting and support
- for the allow,deny,on,off,help sender commands.
- - The default dccp port changed from 5001 to 8000 (suggested by
- Gerrit Renker).
- - para_server starts even if not all public keys could be loaded.
- - Audiod performance improvements.
- - fix a bug in the "off" command of the http sender.
- - fix some fd and memory leaks.
- - Update to gengetopt-2.22.
-
--------------------------------------
-0.3.0 (2008-01-12) "solar saturation"
--------------------------------------
-
-paraslash.0.3.0 -- 'WWDBND --what would databases never do?'.
-
-
-Usually one might expect lots of new features AND a big increase in size
-for a major release like this.
-
-However, paraslash-0.3.0.tar.bz2 is the smallest paraslash tarball
-ever. The decrease in size is mostly due to the removal of some
-graphical tools (which were only quick hacks anyway). But also the
-fact that the mysql code is gone cuts down the size a bit.
-
-Being independent of mysql comes at a cost: The fact that paraslash
-now contains its own database (the object storage layer, osl) increases
-the (stripped) binary size of para_server by ~50K on i386.
-
- - no more restrictions on unique basenames.
- - independent of mysql: The new self-contained object
- storage layer (osl) replaces the mysql database.
- - New executable para_fsck: Check integrity of osl tables.
- - Lyrics support.
- - Reliable audio file move/rename detection.
- - More portable than ever: Tested on Linux (x86_32, x86_64, sparc64),
- MacOS (ppc32, x86_32), FreeBSD (x86_32), NetBSD (x86_32) and
- Solaris (sparc64).
- - the new osl-based audio file selector (afs) replaces the random,
- the playlist and the mysql selector of paraslash-0.2.x.
- - IPv6 support (thanks to Gerrit Renker).
- - paraslash-0.2.x streams are now called "moods". Writing
- 0.3.x-mood definitions should be both easier and more
- powerful than writing 0.2.x-stream definitions.
- - para_krell, para_slider, para_para_sdl_gui, para_dbadm have
- been removed. The world is a better place without them. However,
- para_gui is still there.
- - afs tracks audio file selection also in playlist mode.
- - few easy-to-use afs commands replace the many not-so-easy-to-use
- mysql commands (and are available also in playlist mode).
- - Improved error subsystem.
- - The earth-shaking new logo.
-
------------------------------------------
-0.2.17 (2007-11-20) "isotropic threshold"
------------------------------------------
-
-Mainly bugfixes and cleanups in this version which marks the end of
-the 0.2.x series if no serious bugs show up after the release.
-
- - mysql_selector: fix a locking bug.
- - universal chunk queueing.
- - dccp sender uses chunk queueing if write() returns EAGAIN (thanks
- to Gerrit Renker).
- - be more carful wrt. signed vs. unsigned argument passing.
- - cleanup error.h and fix some references to invalid error
- codes.
- - update to gengetopt-2.21.
- - update to ortp-0.13.1.
- - autoconf: extend checks for headers, library functions and
- compiler characteristics.
- - Fix streaming of large mp3 files.
- - Fix an off-by-one bug in playlist handling.
-
---------------------------------------
-0.2.16 (2007-04-05) "neural discharge"
---------------------------------------
-
-The main change in this release is the major audio format handler
-cleanup which removes some similar/duplicate code and makes it easier
-to implement plugins for other audio formats. Of course, the usual mix
-of other improvements/changes/bugfixes also made it into the release.
-
- - simplified audio format handlers (most of the handling functions
- were moved one layer up to the virtual streaming system).
- - para_server uses mmap to read audio files
- - repositioning of mp3 streams is much faster, in particular for
- jumping near the end of large mp3 files.
- - permission flags DB_READ,DB_WRITE have been renamed to AFS_READ
- and AFS_WRITE.
- - fix a bug in para_filter that caused decoding of aac files
- to start only after a few seconds.
- - fix osx_writer hangs
- - simplified dccp code (thanks to Gerrit Renker)
- - the compress filter works also on big endian systems (ppc)
-
------------------------------------------
-0.2.15 (2007-02-16) "inductive resonance"
------------------------------------------
-
-Minor improvements, more documentation and a bunch of bug fixes.
-
- - para_server: The server.users file is only read once on server
- startup rather than for each connection
- - mp3dec: Fix decoding of corrupt mp3 files
- - afs (audio file sender) is now called vss (virtual streaming
- system). Consequently, the permission flags specified in
- ~/.paraslash/server.users have also changed: AFS_READ and AFS_WRITE
- become VSS_READ and VSS_WRITE respectively.
- - para_audiod/para_filter: Fix a bug that caused the last chunk
- of audio data not being written under certain circumstances
- - audiod: compute the difference of server time and local time
- correctly
- - para_server/para_audiod: Fix some memory leaks
- - documentation improvements
- - configure.ac: fix checks for para_krell
- - new man pages
-
--------------------------------------------
-0.2.14 (2006-10-15) "transient singularity"
--------------------------------------------
-
-The only major enhancement of this version is the osx writer which completes
-the Mac OS Port and was originally planned already for 0.2.13 but had to wait
-until now for reasons beyond the scope of this changelog entry.
-
- - new output plugin for Mac Os: the osx writer
- - rename configure command line options from --enable-xxx-headers to
- --with-xxx-headers and --enable-xxx-libs to --with-xxx-libs
- - configure: new command line options: --with-mad-headers,
- --with-mad-libs, --with-oggvorbis-headers, and --with-oggvorbis-libs
- - some robustness fixes
- - dymamic audio format recognition for audiod
- - para_server: new command line option: --autoplay_delay
- - para_audiod: new command line option: --clock_diff_count
-
----------------------------------------
-0.2.13 (2006-07-14) "sonic convolution"
----------------------------------------
-
-A bunch of new features and core changes.
-
- - the new paraslash scheduler, short and sweet.
- - Support for m4a/mp4 files via the new aac audio format
- handler/filter (requires libfaad).
- - each writer has its own command line parser, just like
- para_recv and para_filter.
- - para_client and para_audioc use the error subsystem
- - writers are integrated in para_audiod (currently linux-only)
- - para_client is integrated in para_audiod
- - random/playlist selector: improved info strings
- - new audiod commands: tasks, kill
- - update to libortp-0.10.1
- - para_fade: wake time defaults to 8 hours from now
- - update to autoconf-2.60
-
-------------------------------------------
-0.2.12 (2006-05-12) "oriented abstraction"
-------------------------------------------
-
-Many user-visible changes in this release and lots of new
-features:
-
-
- - the new optional dccp sender/receiver. It uses the datagram
- congestion control protocol. You'll need a fairly new kernel
- for this.
- - paraslash works on Mac OS X (thanks to Gerd Becker)
- - para_play renamed to para_write
- - modular output plugin design (writers) for para_write
- - new file_writer output plugin for para_write
- - compress filter speed improvements
- - update to libortp-0.9.1
- - update to gengetopt-2.17rc
- - para_client no longer depends on libreadline (as the
- code for the interactive mode was removed).
- - gcc-2-95 is no longer a supported compiler. It may still
- work, but it gets no more testing.
- - the tarball no longer contains the screenshot images which
- reduces its size quite a bit.
- - configure: new command line options: --enable-mysql-headers
- and --enable-mysql-libs
-
-------------------------------------
-0.2.11 (2006-03-11) "atomic duality"
-------------------------------------
-
-Here it is, the first paraslash release developed with git. There
-are fairly many user-visible changes in this release. As two out of
-the three "database tools" of paraslash don't use a database at all,
-they are now called "audio file selectors" instead.
-
-
- - the cdt command (change database tool) becomes chs (change
- selector)
- - no more colon separators: The syntax of some options of
- para_audiod and para_filter have changed. Use --help for
- more info (and some examples).
- - update to gengetopt-2.16 (thanks to Lorenzo Bettini)
- - switch from cvs to git (should've done that earlier)
- - the new ipc subsystem
- - new audio file selector: playlist
- - para_server: the dopey selector is now called "random",
- and is the default selector. Use the --selector option to
- choose another selector at startup, or the chs command to
- change the selector at runtime.
- - X86_64 fixes (thanks to Steffen Klassert)
- - para_play fixes
-
---------------------------------------
-0.2.10 (2006-02-17) "cyclic attractor"
---------------------------------------
-
-Huge documentation update, a scrollable window for para_gui, ortp
-improvements, and of course many small fixes not mentioned here.
-The diffstat below is rather misleading as most insertions are due
-to the new source documentation.
-
- - autoconf cleanup
- - para_server also uses the new error subsystem
- - lots of new documentation (UTSL)
- - gui improvements:
- - keysyms for cursor keys and for next/previous page keys
- - scrollable output window
- - new internal commands: scroll up/down, page up/down
- - fix color of command output.
- - ortp: the --chunk_time and --header flags are no longer needed
- for para_recv/para_audiod as this information is now encoded in
- each rtp packet sent by para_server.
-
--------------------------------------------
-0.2.9 (2006-01-24) "progressive turbulence"
--------------------------------------------
-
-Internal audiod receivers/filters, the new error subsystem and
-a lot of small improvements.
-
- - para_recv and para_filter are integrated into the para_audiod
- binary, i.e. audiod no longer spawns a new process for
- each receiver/filter. As para_recv and para_filter might be
- useful as standalone programs, they still get built (linked
- against the same object files that are also used for audiod).
- - further ortp timing improvements should reduce the CPU usage
- of the ortp receiver.
- - improved audio grabbing. The 'grab' command of para_audiod
- has its own set of command line options. Read the output of
- "para_audioc help grab" for more info.
- - oggdec: configurable input prebuffer size.
- - the new error subsystem gives better error diagnostics
- and reduces code size.
-
------------------------------------------
-0.2.8 (2006-01-02) "dynamic accumulation"
------------------------------------------
-
-The new modular filter design and the para_play-hangs bugfix.
-
- - new executable: para_filter. It combines para_mp3dec,
- para_oggdec and para_compress. It also adds a further filter
- type, wav, that just inserts a wave header at the desired point
- of the filter chain. All 'piping' is done in-memory (i.e. no
- read/write operations are used).
- - para_play: fix a stupid bug that caused it to hang under
- certain circumstances.
-
--------------------------------------------
-0.2.7 (2006-12-27) "transparent invariance"
--------------------------------------------
-
-Not many user-visible changes but a fair amount of internal improvements.
-
-
- - The http sender buffers data if it can not be sent
- out immediately (because the socket is not writable). This
- should prevent para_server from shutting down the connection
- too early on a loaded network.
- - para_play also prebuffers data if it is told to start at a
- future time by the --start_time option.
- - The return of para_recv: It combines para_ortp_recv and
- para_http_recv. Use the --receiver option to switch between
- the two. para_recv builds without libortp, but contains
- only the http receiver in this case.
- - update to ortp 0.8.1. As this ortp release contains incompatible
- changes, para_recv-0.2.7 won't link against older ortp libs.
- - improved ortp timings.
- - use of gcc-extensions that #define away for non-gcc and
- gcc < 3.0.
-
--------------------------------------------
-0.2.6 (2005-10-29) "recursive compensation"
--------------------------------------------
-
-Transparent session encryption (uses openssl's Alleged RC4 cipher),
-the internal find command and several other improvements and cleanups.
-
- - Encrypt the session if encryption is requested by the client
- (default for para_client 0.2.6). This is backwards
- compatible, so older clients can still connect to para_server
- 0.2.6. Use the new client option --plain to request an
- uncrypted session (off by default, must be set to on in
- order to connect to para_server 0.2.x with 0 <= x <= 5).
- - para_server uses an internal function to locate audio files
- rather than calling find(1). The server option
- --mysql_audio_file_dir replaces --mysql_find_cmd.
- - documentation update
- - man pages
- - header file cleanup
- - para_client code cleanup
- - para_gui: faster display of output of display commands
-
-------------------------------------------
-0.2.5 (2005-10-13) "aggressive resolution"
-------------------------------------------
-
-This release adds internal senders, i.e. no more external programs are
-spawned for sending out the audio data. There are two different senders
-available: The http sender and the ortp sender (former para_send which
-is no longer needed).
-
-The new sender code has a plugin-like design so it can be easily
-extended should there be be any future need for supporting another
-network streaming protocol. All senders are completely independent of
-each other. In particular, the http and the ortp sender can operate
-in parallel.
-
- - new server command: sender to control senders at runtime.
- Read the output of "para_server -h" and "para_client help
- sender" for more information.
- - para_recv renamed to para_ortp_recv
- - new executable: para_http_recv, a simple command line
- http receiver.
- - major afs/mp3/ogg code simplifications due to internal
- senders.
- - ogg timing improvements
- - fix several minor memory leaks (found by valgrind)
- - empty stream definitions work again
- - com_ne(): ignore errors on remove
- - audiod: fix segfault on server restart
-
----------------------------------------
-0.2.4 (2005-09-21) "toxic anticipation"
----------------------------------------
-
-Several small improvements, fixes and the new grab command.
-
- - audiod:
- - new command: "grab" to grab the output of the stream reader
- or any filters. Read the output of "para_audioc help grab"
- for more information.
- - fix memory leak
- - code cleanup
- - audioc: new command line option: --bufsize to specify a
- buffer size different from the default size 8192.
- - improved error diagnostics for para_play.
- - new configure option: --enable-ssldir so search for openssl in
- non-standard places
- - sdl_gui: Make it look nice again for 1024x768
- - server: report total size of memory allocated with sbrk by malloc,
- new command line option: --announce_time
-
------------------------------------------
-0.2.3 (2005-09-01) "hydrophilic movement"
------------------------------------------
-
-Two new executables and major feature enhancements.
-
- - audiod filters: It is now possible to specify arbitrary many
- (including none) filters for each supported audio
- format. This can be used e.g. for normalizing volume,
- transforming or grabbing the audio stream, or for using
- visualizers. Read the output of "para_audiod -h" for the
- syntax of the new --filter_cmd option.
- - new executable: para_play, a tiny alsa player. It
- can play wave files or raw pcm (16 bit little endian)
- from stdin.
- - new executable: para_compress, a dynamic range compressor
- intended to keep audio output at a consistent volume. Derived
- from AudioCompress, http://trikuare.cx/code/AudioCompress.html.
- - audiod: New option: --stream_delay. This can be used in
- a local network to syncronize the audio output of all
- clients that play the same stream.
-
-------------------------------------------
-0.2.2 (2005-08-19) "tangential excitation"
-------------------------------------------
-
-Mostly internal changes in this release, but also some new commands
-for the mysql database tool.
-
- - cleanup exec.c, fix para_exec bug
- - compile time loglevel (log messages below the given level
- won't be compiled in, which reduces the size of the
- resulting binaries)
- - new log macros that shorten the size of the source code.
- - workaround a gcc-4.1 bug (?) that caused send_cred_buffer()
- to send only zeros. With this workaround, para_audioc works
- again.
- - avoid gcc-4 warning: conflicting types for built-in function 'clog'
- - new mysql commands: "rm" (remove entry), "mv" (rename entry) "ne"
- (new entry), "snp" (set numplayed). Read the manual for more
- information.
-
----------------------------------------
-0.2.1 (2005-08-15) "surreal experience"
----------------------------------------
-
-Here comes paraslash-0.2.1. It contains a couple of new features and,
-surprise, only minor bug fixes.
-
- - kill noisy mp3 debug message
- - cleanup of the build system
- - para_server and para_client directly use the crypto routines
- of the openssl library rather than invoking the openssl command
- line utitlity
- - server/audiod: new option --user to switch to the given user
- when invoked as root. Read the output of "para_server -h" for
- more information.
- - gui/sdl_gui: new option --stat_cmd to be used to retrieve the
- status. Default: "para_audioc stat"
- - sdl_gui: new option --pic_cmd to be used to download the picture.
- Default: "para_client pic"
- - audiod: 5 slots ought to be enough for everybody
- - audiod: new status item: Uptime, kill hup command
-
-------------------------------------------
-0.2.0 (2005-08-06) "distributed diffusion"
-------------------------------------------
-
-After several month of increased development activity, paraslash-0.2.0
-has arrived. It contains many new features and is much more
-self-contained than the old 0.1.x series. Enjoy!
-
-
- - para_server: fix hang on song change and crash on sighup.
- Speed up mysql queries. The DIR_LIKE macro is gone.
- - new executables: para_audiod, the local audio daemon that
- starts playback (uses SCM_CREDENTIALS socket magic) and
- para_audioc, the corresponding client.
- - new executables: para_mp3dec/para_oggdec, two really teensy
- decoders. para_mp3dec is based on libmad, para_oggdec requires
- libvorbisfile.
- - ovsend/ovrecv are capable of streaming ogg as well as mp3, so
- they are now called para_send and para_recv respectively.
- - documentation updates
- - para_gui is themable. For now there is the default theme that
- looks as before and the simple theme: blue and easy.
- - gui: audio streaming is now handled by audiod. Time display shows
- playback time rather than streaming time
- - slider: update to libzmw-0.2.0
- - para_krell: fix crash on server shutdown
- - switch from gzip to bzip2
-
-----------------------------------------
-0.1.7 (2005-04-18) "melting penetration"
-----------------------------------------
-
-The main change in this release is clearly the oggvorbis rewrite,
-but there are also lots of smaller changes. If you intend to use both
-the mp3 and the ogg plugin, it is recommended to use software mixing,
-e.g. the dmix plugin which is provided by ALSA.
-
- - new executables: para_ovsend and para_ovrecv for sending/receiving
- oggvorbis files via rtp. Requires the open rtp library. Get it at
- http://www.linphone.org/ortp/
- - rewrite of the ogg_vorbis core code
- - configure detects libzmw and, if detected, includes
- para_slider to the list of binaries to be built by make
- - server stream writers read from their associated fifo rather
- than from stdin
- - slider: two new sliders, lastplayed and numplayed
- - fix nasty double free bug which caused random segfaults in case of
- mp3 files with invalid header information
- - gui: new command line option: --stream_timeout=seconds to
- deactivate a slot if it is idle for that many seconds (default=`5')
- - diffstats
-
----------------------------------------
-0.1.6 (2005-03-05) "asymptotic balance"
----------------------------------------
-
-Only little user-visible changes in this release. Mainly bugfixes and
-core code cleanup. This is probably the most stable version ever if you
-stick to mp3...
-
- - fix several memory leaks
- - rename default name of mysql database from "music" to "paraslash".
- Use para_server's --mysql_database option if you do not want to
- rename your old database.
- - rework ogg vorbis code
- - make update command work on mysql servers with LOCAL_INFILE
- disabled
- - gui: improved stream I/O (slots)
- - simplified audio format API
- - para_pob_ogg is gone
-
-------------------------------------
-0.1.5 (2004-12-31) "opaque eternity"
-------------------------------------
-
-Let's slide gently into the new year.
-
- - new: para_slider (not built automatically, type "make
- para_slider" to build). A toy for those who always felt that
- creating stream definitions is difficult. See screenshots,
- README and FEATURES for more info.
- - improved signal handling. Fixes server segfault on SIGHUP
- for linux kernels newer than Aug 24 2004 and makes para_gui
- race-free.
- - reload database tool on SIGHUP
- - improved help message for sl
- - do not log "broken pipe" messages as errors. They are
- perfectly ok.
- - fix wrong error message on permission errors
-
------------------------------------------
-0.1.4 (2004-12-19) "tunneling transition"
------------------------------------------
-
-Bugfix release. As expected, 0.1.3 introduced a bunch of new bugs.
-Hopefully, most of them got wiped out with this release. Some
-enhancements went also in.
-
- - improved error diagnostics for all commands
- - stradd/picadd: overwrite previous contents if entry already
- exists, rather than returning errors
- - stradd: use current stream if invoked without args
- - faster (and hopefully more stable) ogg-vorbis handling
- - para_krell: reap children to avoid zombie-flooding in case
- no server is running
- - si: report also server pid
- - server: don't busy-loop if dbtool reports only invalid files.
- - gui: CTRL+C works again, fix stream_read command line option
- - fix pic_add, hist
- - fix mysql dbtool startup in case no database exists
- - many small fixes and cleanups
-
----------------------------------------
-0.1.3: (2004-12-10) "vanishing inertia"
----------------------------------------
-
-Starting from this release, the database tools are integrated in the
-server binary. This decreases server startup time, reduces code size
-and speeds up database commands. However, the layout of the underlying
-mysql database changed only slightly and 0.1.3 should be backwards
-compatible in that respect.
-
-Visible changes:
-
- - If mysql is not detected at compile time, or fails to init
- at runtime, fall back to the dopey database tool which should
- always work.
- - para_dbtool and dbtool.conf are gone. All mysql specific
- options are read from server.conf and are prefixed by 'mysql_'.
- - new command: cdt (change database tool)
- - new command line option: dbtool (choose startup database tool)
- - The name of current stream is now stored in the database,
- so paraslash remembers its current stream when restarted.
- - new command: csp (change stream and play)
- - para_gui also reports current database tool and server uptime
-
--------------------------------------------
-0.1.2: (2004-11-28) "spherical fluctuation"
--------------------------------------------
-
-Point release before the big dbtool changes go in.
-
- - dbtool: rename ca to cam (copy all meta data). It now also
- copies numplayed and lastplayed time as well as the picture
- id.
- - fix endless-loop-bug caused by mp3 files with invalid header
-
------------------------------------------
-0.1.1: (2004-11-05) "floating atmosphere"
------------------------------------------
-
- - gkrellm plugin
- - new dbtool command: mbox. Browse your sound-file collection
- with your favorite mail reader.
- - several small fixes
-
--------------------------------------
-0.1.0: (2004-10-22) "rotating cortex"
--------------------------------------
-
- - fix logging bug for loglevel > VERBOSE
- - fix skip command
- - correct timings for vbr mp3s
- - modular audio format support
- - ogg-vorbis support (experimental)
- - new server option: autoplay
-
------------------------------------------
-0.0.99: (2004-07-25) "harmonic deviation"
------------------------------------------
-
- - rename projectname from icc to paraslash (play, archive, rate
- and stream large audio sets happily)
- - paraslash is no longer restricted to one particular audio
- streaming software
- - new dbtool commands (stradd, strq, strdel) for easy stream
- managment w/o configuration file. That obsoletes stream_defs
- file/config option for dbtool.
- - picadd accepts jpeg data from stdin
- - new server commands: ps (select previous stream), sc (song change)
- - new default pictures for sdl_gui
- - gui: new key_map option for binding commands and internal
- functions to arbitrary keys, nice help screen, rip out
- soundcard/linux specific stuff, avoid noise artefacts while jumping,
- show silly logo on startup
- - new executables: para_fade for fading volume, para_dbadm for
- manipulating attributes
- - cdb adds _all_ tables to mysql database
- - revised and beautified documentation
- - sample dbtool rewritten in C
- - autoconf
-
----------------------------------------------
-0.0.98: (2003-12-26) "incremental smoothness"
----------------------------------------------
-
- - kick icecast in favour of poc. That removes some races and reduces
- core code considerably.
- - cbr/vbr is displayed by stat and gui/sdl_gui. New status flags
- give finer info on afs' status.
- - gui can start decoder (see config options). Further new gui
- commands: refresh (^L), jmp (F1-F10)
- - gui rereads conf on SIGUSR1 instead of SIGHUP. SIGHUP
- terminates gui. This fixes dead instances consuming memory
- continuously.
- - new dbtool command: verb for sending verbatim sql queries.
- - fix pid_list races (by removing pid_list)
- - codename funnies
-
---------------------
-0.0.97: (2003-10-26)
---------------------
-
- - installation prefix now defaults to /usr/local
- - new commands for gui: snozze, sleep and reread config
- - config file for gui and sdl_gui
- - fix problems with filenames containing funny characters
- (reported by Thomas Forell)
- - improved signal handling for gui, now it rereads conf on SIGHUP
- - new dbtool command: cdb (create database)
- - switch from argtable to gengetopt
- - major code cleanup and speed improvements
- - fix several potential buffer overflows
- - many small fixes and cleanups
-
--------------------
-0.0.96 (2003-08-30)
--------------------
-
- - easy stream_defs syntax
- - sdl_gui can display images associated to the file being played
- - Major feature enhancements for icc_gui including dynamic text
- placement and the top/bottom window design
- - vrfy/clean now also checks for NULL values in attributes as
- well as for invalid picture pointers
- - fix long outstanding case sensitivity bug
- - many small fixes and cleanups
-
--------------------
-0.0.95 (2003-06-29)
--------------------
-
- - sdl gui runs much faster
- - new dbtool command: ca (copy attributes)
- - count and display number of times the song has been played
- - new feature: scoring
- - command line options for sdl_gui
- - simpler syntax of streams file
- - decrease network traffic of stat
- - fix zombie bug
- - many small fixes and cleanups
-
--------------------
-0.0.94 (2003-05-04)
--------------------
-
- - new server command: ns (next stream)
- - new icc_gui command: c (change stream)
- - internal mp3info
- - stat shows also id3 tag info
- - new sdl based gui
- - log flodding bug fixed
- - many small fixes and cleanups
-
--------------------
-0.0.93 (2003-03-28)
--------------------
-
- - colors for icc_gui
- - icc_gui sets volume directly (linux only)
- - proper locking that fixes some races
- - fix security bug that caused commands to be executed even
- with unsufficient permissions
- - new command: hup to make all servers reread their configuration file
- - icecast meta data streaming
- - many small fixes and cleanups
--- /dev/null
+NEWS
+====
+
+------------------------------------------
+current master branch "cascading gradient"
+------------------------------------------
+
+- para_afh learned to modify meta tags of mp3 wma ogg spx
+ opus flac aac files.
+- afs commands propagate error codes to the client.
+- The check command now also checks the attribute table for
+ inconsistencies.
+- New -v flag for the version command (print verbose version string)
+- New option --priority for para_server and para_audiod.
+
+
+--------------------------------------
+0.5.5 (2015-09-20) "magnetic momentum"
+--------------------------------------
+
+Many new features and a lot of other improvements.
+
+- On Linux systems, local sockets are now created in the
+ abstract name space by default. This allows to get rid of
+ the socket specials in /var/paraslash.
+- The --user-allow option of para_audiod now accepts also
+ usernames rather than only user IDs.
+- New autoconf macros to avoid duplication in configure.ac.
+- Status items (as shown by para_gui) are updated correctly
+ when the meta information of the current audio changes.
+- para_server and para_audiod no longer refuse to start in
+ the background if no log file is given. Instead, all log
+ messages go to /dev/null in this case.
+- Web page cleanup.
+- New syntax for the -l and -s options of the ls command.
+ These options should now be specified as -l=v rather than
+ -lv, for example. The old syntax still works, but support
+ will be dropped in v0.6.0.
+
+Downloads:
+[tarball](./releases/paraslash-0.5.5.tar.bz2),
+[signature](./releases/paraslash-0.5.5.tar.bz2.asc)
+
+------------------------------------------
+0.5.4 (2015-01-23) "exponential alignment"
+------------------------------------------
+
+Another cleanup and bugfix release.
+
+- New server command: tasks.
+- Minor cleanups to daemon.c.
+- New URLs for home page and git services.
+- Improved error diagnostics for the mvblob commands.
+- New sender subcommand: status.
+- Improved help text for server and afs commands.
+- audiod memory leak fixes.
+- Miscellaneous improvements to the build system.
+- oss_writer improvements.
+- Improved handling of mp3 files with both id3v1 and id3v2 tags.
+
+Downloads:
+[tarball](./releases/paraslash-0.5.4.tar.bz2),
+[signature](./releases/paraslash-0.5.4.tar.bz2.asc)
+
+---------------------------------------------
+0.5.3 (2014-08-01) "symbolic synchronization"
+---------------------------------------------
+
+Not many new features, but lots of fixes and usability improvements.
+
+- para_gui has been converted to use the paraslash scheduler.
+- Various alsa-related fixes, mostly for the raspberry pi.
+- Many scheduler improvements and cleanups.
+- The test suite has been extended to include sanity checks
+ for the generated man pages.
+- ao_writer fixes. This writer was in a quite bad shape. Many
+ serious bugs have been fixed.
+- new audiod command: version.
+- Minor improvements to the bitstream API.
+- The cpsi command now prints a meaningful error message if
+ none of the given patterns matched any audio file.
+
+Downloads:
+[tarball](./releases/paraslash-0.5.3.tar.bz2),
+[signature](./releases/paraslash-0.5.3.tar.bz2.asc)
+
+----------------------------------------
+0.5.2 (2014-04-11) "orthogonal interior"
+----------------------------------------
+
+The new sync filter, the AES_CTR128 stream cipher and the overhauled
+network code are the highlights of this release. It also includes a
+fair number of smaller fixes and improvements not mentioned here.
+
+- The new sync filter synchronizes playback between multiple
+ clients.
+- Connections between para_server and para_client are now
+ encrypted by means of AES rather than RC4 if both sides
+ support it. RC4 is still available as a fallback. This
+ feature is fully transparent, i.e. no command line options
+ are necessary, and a client linked against openssl can
+ speak with a server linked against libgcrypt and vice versa.
+- Major cleanup of the networking subsystem.
+- Improvements to para_fade: the new set mode, multi-channel
+ initial volumes, better error logging.
+- The man pages of para_audiod, para_filter, para_recv, and
+ para_write contain the relevant options for receivers, filters,
+ writers. This broke in 0.5.0.
+- ogg/vorbis latency improvements.
+- Improved user manual.
+- Minor fixes to avoid clang warnings.
+
+Downloads:
+[tarball](./releases/paraslash-0.5.2.tar.bz2),
+[signature](./releases/paraslash-0.5.2.tar.bz2.asc)
+
+------------------------------------------
+0.5.1 (2013-12-20) "temporary implication"
+------------------------------------------
+
+Lots of fixes and improvements all over the place, and a major overhaul
+of the build system.
+
+- Audiod improvements and fixes.
+- Buffer tree robustness improvements.
+- Cleanup of the mood subsystem.
+- Fixes and cleanups for the flac decoder.
+- Latency improvements for the ogg/opus decoder.
+- Crypto support is now optional. On systems without
+ openssl/gcrypt, the build succeeds but para_server,
+ para_audiod, para_client won't be built.
+- The build system now works for cross-compile setups.
+- The dependency tree has been flattened, which speeds up
+ builds and avoids to recreate the man pages on every change.
+- The error code helper has been rewritten from perl to C,
+ which further improves build time.
+- Many small bugs in the build system have been identified
+ and fixed.
+
+Downloads:
+[tarball](./releases/paraslash-0.5.1.tar.bz2),
+[signature](./releases/paraslash-0.5.1.tar.bz2.asc)
+
+----------------------------------------
+0.5.0 (2013-08-23) "invertible validity"
+----------------------------------------
+
+Some API-breaking changes, one serious bug fix, and a lot of bike-shedding.
+
+- The sideband compatibility code has been removed, hence
+ sideband connections (introduced in 0.4.11) are now mandatory.
+- Addblob commands can produce output.
+- The stat command no longer sends garbage when para_server was
+ compiled against libgcrypt.
+- Dependencies for gengetopt files are computed automatically.
+ This eliminates a constant source of build bugs.
+- The setatt command now accepts file name patterns rather than only
+ path names.
+- overview.pdf is now based on dia, a simple diagram creation program.
+ The new version is much more detailed and contains descriptions of
+ the various programs of the paraslash package.
+- The separator of all multi-word options has been changed from
+ underscore to dash. For example --log_color becomes --log-color.
+- Overhauled web pages and the new logo.
+
+Downloads:
+[tarball](./releases/paraslash-0.5.0.tar.bz2),
+[signature](./releases/paraslash-0.5.0.tar.bz2.asc)
+
+--------------------------------------
+0.4.13 (2013-07-29) "spectral gravity"
+--------------------------------------
+
+One more 0.4.x release before the API-breaking changes for 0.5.0 go
+in. The main features of this release are the ogg/opus audio format,
+and UTF-8 support, but it includes also tons of other improvements
+and fixes all over the place.
+
+- New audio format: ogg/opus.
+- UTF8 support for para_gui and the mp3 audio format handler.
+- Scheduler improvements and fixes.
+- The obsolete gettimeofday() function has been replaced
+ by clock_gettime() on systems which support it.
+- Speed and usability improvements for para_gui.
+- para_client now restores the fd flags of stdin and stdout
+ on shutdown.
+- Improved manual pages.
+- Consistent version strings for all executables.
+- Reduced dependencies on generated files result in fewer
+ recompilations on changes.
+- Performance improvements for the compress filter.
+- Improved downloads web page.
+
+-----------------------------------------
+0.4.12 (2012-12-20) "volatile relativity"
+-----------------------------------------
+The new command line player, the resample filter, ALSA support for
+para_fade, and the improved build system are the highlights of this
+release which probably marks the end of the 0.4.x series.
+
+- The afh receiver and the para_play executable.
+- The resample filter: A sample rate converter based on
+ libsamplerate.
+- The "versions" directory has been removed from the master
+ branch. The tarballs of the old releases are now available
+ in the new "releases" branch.
+- Overhaul of the build system: All generated files are now
+ written to the "build" directory.
+- The modular mixer API and the alsa mixer.
+- Minor fixes for the osx writer.
+
+--------------------------------------
+0.4.11 (2012-07-20) "mutual diversity"
+--------------------------------------
+
+The major feature in this release is the new sideband API for
+client-server communication. This API will be used exclusively starting
+with 0.5.0, which breaks backward compatibility but allows to get rid
+of quite some compatibility code. Other noteworthy changes include
+decoder latency improvements and a long-standing bug fix for the
+ALSA writer.
+
+- Sideband connections: If both para_server and para_client
+ support this feature, data is sent as a multiplexed stream.
+- The --no_default_filters option of para_filter has been
+ removed.
+- Several fixes and latency improvements to various decoders.
+- The ALSA writer now limits the prebuffer time to 500ms.
+- Documentation improvements.
+- Overhaul of the command_util.sh script.
+- Fixes for some minor problems found by the clang analyzer.
+- Compiles (almost) without warnings on gcc-3.
+- Robustness improvements of the buffer tree code.
+
+------------------------------------------
+0.4.10 (2012-03-30) "heterogeneous vacuum"
+------------------------------------------
+
+Nothing earth-shaking in this release, but quite a few usability
+improvements and the usual mix of cleanups and fixes.
+
+- The --no_default_filters option of para_filter has been
+ deprecated. It still works but has no effect and will be
+ removed in the next version.
+- para_gui now prints also the stderr output of the executing
+ command in the bottom window.
+- Cleanup and consolidation of the various wrappers for
+ write(), writev(), send() and friends.
+- The obscure error messages on mmap() failures have been
+ replaced by meaningful messages. This affects mainly
+ para_afh.
+- para_audioc: Cleanups and memory leak fixes.
+- Test 0004-server no longer fails if para_server is not
+ being built.
+- New configure options: --with-id3tag-{headers,libs}.
+
+-------------------------------------
+0.4.9 (2011-12-06) "hybrid causality"
+-------------------------------------
+
+Support for another audio format, interactive mode for para_client
+and para_audiod and many small improvements/fixes all over the place.
+
+- Support for flac, the free lossless audio codec.
+- Fix for an endless loop in the mp3 decoder for certain
+ (corrupt) mp3 files.
+- When executed without specifying a command, para_client
+ and para_audioc start an interactive shell (requires
+ libreadline being installed). The interactive mode offers
+ full tab completion and command line history.
+- autogen.sh now detects a distcc setup and adjusts the
+ parameter for the -j option of make accordingly.
+- Shared memory areas are no longer restricted to 64K. We now
+ detect the maximal size of a shared memory area at runtime.
+- cleanup of the internal uptime API.
+- para_server prefaults the mmapped audio file to avoid
+ delays on slow media.
+- A new test for the test-suite that exercises the
+ communication between para_server and para_audiod.
+- The alsa writer eats up less CPU cycles when configured to
+ use the DMIX plugin.
+- Simplified and unified receiver code.
+- Makefile cleanups.
+- Commands which print a list of matching audio files now
+ emit a meaningful error message if no audio file matched the
+ given pattern(s).
+
+--------------------------------------
+0.4.8 (2011-08-19) "nested assignment"
+--------------------------------------
+
+Gcrypt support, the overhauled osx writer and regex format specifiers
+are the highlights of this release.
+
+- support for libgcrypt as a drop-in replacement for openssl.
+ Run configure --enable-cryptolib=gcrypt to link against
+ libgcrypt. The two crypto implementations are compatible to
+ each other, i.e. a para_client executable linked against
+ gcrypt can connect to para_server linked against libssl
+ and vice versa.
+- Rewrite of the osx writer (output plugin for Mac OS).
+- audiod: The format specifier for receivers, filters and
+ writers is now treated as a regular expression. This allows
+ to replace 5 lines in the config file (one for each audio
+ format) by one single line. See the manual for details.
+- The \*.cmdline.[ch] files are no longer contained in the released
+ tarballs. This reduces the size of the tarballs but requires
+ gengetopt to build the tarball.
+- Compiles cleanly also with llvm/clang.
+- Corrupt mp3 files are handled more gracefully.
+- The alsa writer uses poll fds instead of computing timeouts.
+- Cleanup of the generic writer API.
+- sched: Optimized zero timeouts.
+- vss timeout cleanups.
+- oggdec fixes and improvements.
+
+--------------------------------------
+0.4.7 (2011-06-01) "infinite rollback"
+--------------------------------------
+
+The new ao writer, support for ssh RSA keys and a couple of other
+enhancements.
+
+- Support for ESD, Pulseaudio, AIX, Solaris, IRIX and other
+ platforms through the libao audio library.
+- Support for RSA keys generated with ssh-keygen.
+- configure: improved options for ogg/vorbis/speex.
+- The git version reported by --version always matches HEAD.
+- The autogen script detects the number of processors and
+ runs a parallel make if possible.
+- Major cleanup of the crypto API.
+- Documentation updates.
+
+------------------------------------------
+0.4.6 (2011-03-31) "deterministic entropy"
+------------------------------------------
+
+Lots of ogg/vorbis improvements, the new test suite, enhancements
+for para_gui and a fair amount of other bug fixes.
+
+- For DCCP/OGG streams the audio file header is only sent once
+ at the beginning of the stream rather than periodically
+ every five seconds. This reduces network traffic and the
+ FEC group size.
+- The vorbis comment header is replaced by an empty dummy header
+ before the header is sent over the network. This also results in
+ less network traffic and smaller FEC groups.
+- The new "test" make target allows to perform some sanity checks prior
+ to installing the package.
+- ogg timing fixes and performance improvements
+- Scheduler improvements
+- Proper exit codes for para_write
+- para_gui: New option --theme to select a startup theme. Several
+ other improvements and fixes.
+- aacdec error message cleanups
+- simplified color error handling
+
+--------------------------------------------
+0.4.5 (2010-12-17) "symmetric randomization"
+--------------------------------------------
+
+Bug fixes, internal cleanups and variable-sized FEC slices.
+
+- Contains a fix for an invalid-free-bug in the ogg audio format
+ handler code.
+- Switching off the DCCP sender works again.
+- para_audiod handles crashes of para_server more robustly.
+- Internal scheduler and writer cleanups.
+- Reduced latency due to variable-sized FEC slices.
+- Improved documentation and error diagnostics.
+- The build of para_server is now optional, allowing the build
+ to succeed in case libosl is not installed.
+
+------------------------------------------
+0.4.4 (2010-08-06) "persistent regularity"
+------------------------------------------
+
+Support for yet another audio format, para_write improvements and
+bug fixes.
+
+- Support for the speex codec.
+- Support for sample formats other than 16 bit little endian.
+- error2.h is now created by a perl script which speeds up configure
+ considerably.
+- Fix a bug in the aac decoder which could lead to segfaults in
+ para_filter/para_audiod.
+- Fixes for autoconf-2.66.
+
+----------------------------------------
+0.4.3 (2010-07-05) "imaginary radiation"
+----------------------------------------
+
+Many improvements for the DCCP and the UDP transport, the new user
+manual and the usual mix of bug fixes and internal improvements.
+
+- FEC support for the DCCP sender (Gerrit Renker). The new
+ --dccp_max_slice_size, --dccp_data_slices_per_group and
+ --dccp_slices_per_group options can be used to set the FEC
+ parameters for the DCCP transport.
+- DNS lookups for UDP targets (Gerrit Renker).
+- The new user manual replaces the README, README.afs, REQUIREMENTS
+ and INSTALL documents.
+- Fix an end-of-file detection bug in the oggdec filter.
+- The new nonblock API.
+- Both options of the oggdec filter have been removed.
+- New debug mode for the internal scheduler.
+
+------------------------------------------
+0.4.2 (2010-04-23) "associative expansion"
+------------------------------------------
+
+It's been some time since the last release, but finally here is
+paraslash-0.4.2. The bulk of the changes comes from the new buffer
+tree API, but there are changes all over the tree. Mainly performance
+and usability improvements, but also quite some bug fixes.
+
+- The new buffer tree API.
+- DCCP: Support for CCID negotiation (Gerrit Renker).
+- UDP robustness fixes.
+- The --bufsize option for mp3dec is gone as it no longer makes sense
+ for the new buffer tree API.
+- Fix audible buffer underruns for wma streams.
+- The alsa writer no longer prints meaningless underrun durations.
+- audiod: Defaults work also for udp streams. If no filter is
+ given for an audio format that is received via upd, fecdec is
+ automatically added as the first filter (along with the decoder).
+
+---------------------------------------
+0.4.1 (2009-12-22) "concurrent horizon"
+---------------------------------------
+
+Support for another audio format, minor feature enhancements and lots of bug
+fixes. All fixes that have been accumulated in the maint branch (in particular
+those mentionened in the 0.3.6 release notes) appear in this release as well.
+
+- wma support.
+- new afh option: --human to activate human-readable output.
+- new server/audiod option: --log-timing to print timing information.
+- build system improvements.
+- source code documentation updates.
+
+-------------------------------------
+0.3.6 (2009-12-07) "cubic continuity"
+-------------------------------------
+
+Quite a few bugs have been found and fixed since 0.3.5, so here's
+another 0.3.x release. No new features.
+
+- Always check return value of malloc().
+- ogg vorbis/FEC: Do not write garbage after the audio file header.
+- exit if root privileges could not be dropped.
+- FEC: Fix computation of extra slices.
+- oss: Fix check for empty input buffer.
+- Avoid buffer underruns due to filter chain output buffer constraints.
+- server: Fix assignment of afs_pid.
+- Don't panic if the afs database contains unknown audio formats.
+- http/dccp: Do not send the audio file header twice.
+- FEC: Timing improvements.
+
+----------------------------------------------
+0.4.0 (2009-11-10) "simultaneous independence"
+----------------------------------------------
+
+Two significant changes which require the new version number: The
+improved authentication dialog and the fact that the database code
+has been moved to a library, libosl. To use the new version, you have
+to generate new RSA keys, see INSTALL for details. A shell script is
+provided for conversion of the 0.3 database to the new 0.4 format.
+
+- stronger crypto for client authentication
+- the database code has been moved to a library
+- improved status item handling
+- cleanup of the build system
+- The "-V" option now also prints the git version
+- the new parser-friendly listing mode for the ls and stat commands
+- mandatory rc4 encryption
+- major audio format handler cleanups
+- (id3,...) tags are no longer stored as a combined string in the database
+- new mood methods: artist_matches, title_matches, comment_matches,
+ album_matches, year_maches, year.
+
+--------------------------------------------
+0.3.5 (2009-09-21) "symplectic separability"
+--------------------------------------------
+
+Full client support for \*BSD Unixes, complete re-write of the ogg
+vorbis audio format handler, various improvements all over the place
+and the usual mix of bugfixes. This release marks the end of the 0.3
+series if no serious problems show up.
+
+- the new oss writer (supported on \*BSD and Linux)
+- rewrite of the ogg vorbis audio format handler. It's
+ recommended to replace the chunk tables of existing ogg
+ vorbis files in the afs database by re-adding these files
+ with "add -f".
+- support for netmask subsets (Gerrit Renker)
+- the new prebuffer filter
+- improved signal handling
+- variable fec output buffer size
+- improved FEC timing fixes audible buffer underruns in UDP mode
+- --log_color actually works
+- new ls option: -d (print dates as seconds after the epoch)
+- update to gengetopt 2.22.2
+- support for RSA keys of size > 512 bits
+- new option "mixer_channel" for para_fade
+
+-----------------------------------------
+0.3.4 (2009-05-07) "elliptic inheritance"
+-----------------------------------------
+
+The new udp sender, forward error correction, colored logs and various
+other improvements. As the udp sender does not depend on any special
+libraries, it is built unconditionally.
+
+- The udp sender replaces the ortp sender. The new code uses forward
+ error correction to protect against packet losses. Many thanks to
+ Gerrit Renker for providing ipv6 support.
+- The default port for udp streaming now defaults to 8000, like
+ for the http and the dccp senders/receivers.
+- Loglevels are now specified as symbolic names, e.g.
+ "--loglevel info".
+- improved ipv4 and ipv6 URI parser (Gerrit Renker).
+- para_server/para_audiod: Color support for log messages.
+- new options for mp3dec: --ignore-crc, --bufsize
+- new audiod option: --config-file.
+- gengetopt cleanups.
+- Improved help/man pages: The documentation of para_audiod,
+ para_recv, para_filter and para_write now also contains
+ all options of the available receivers/filters/writers. The
+ man page of para_fade contains a description of the different
+ modes of operation.
+- More source code documentation.
+- vss timing fixes.
+
+--------------------------------------------
+0.3.3 (2008-12-01) "axiomatic perspectivity"
+--------------------------------------------
+
+Internal code cleanups, bug fixes, improved tag handling and the new
+amplification filter.
+
+- para_server uses the generic scheduling code.
+- overhaul of the virtual streaming system.
+- mp3: id3 version 2 support via libid3tag (optional)
+- ogg: vorbis comment support.
+- aac meta info support.
+- mp3 audio format handler cleanups.
+- new filter: "amp" to amplify the amplitude of the audio stream
+- new status item/database entry: amplification. It is
+ used by the amp filter to pre-amplify the audio stream.
+- fix a close-without-open bug in para_write.
+- fix a bug in com_init() which was introduced in 0.3.2.
+- better error diagnostics for para_client.
+
+-----------------------------------------
+0.3.2 (2008-04-11) "probabilistic parity"
+-----------------------------------------
+
+The new para_afh executable, scheduling and documentation improvements.
+
+- new ls option: -lc (list chunk table)
+- new executable: para_afh, the stand-alone audio file handler tool
+- afs commands can send output more than SHMMAX (32MB on Linux). This
+ also reduces the memory usage of commands that produce large amounts
+ of output.
+- major scheduler and audiod cleanups.
+- more detailed and much nicer man pages.
+
+---------------------------------------
+0.3.1 (2008-02-23) "liquid interaction"
+---------------------------------------
+
+A mix of cleanups, bug fixes, improvements, and some new features. No
+significant changes to the new database (osl) code, which is generally
+a good sign.
+
+- Share some similar/duplicate code between the http and the
+ dccp sender.
+- Generic access control lists for paraslash senders.
+- dccp sender: Access control lists, connection limiting and support
+ for the allow,deny,on,off,help sender commands.
+- The default dccp port changed from 5001 to 8000 (suggested by
+ Gerrit Renker).
+- para_server starts even if not all public keys could be loaded.
+- Audiod performance improvements.
+- fix a bug in the "off" command of the http sender.
+- fix some fd and memory leaks.
+- Update to gengetopt-2.22.
+
+-------------------------------------
+0.3.0 (2008-01-12) "solar saturation"
+-------------------------------------
+
+paraslash.0.3.0 -- 'WWDBND --what would databases never do?'.
+
+
+Usually one might expect lots of new features AND a big increase in size
+for a major release like this.
+
+However, paraslash-0.3.0.tar.bz2 is the smallest paraslash tarball
+ever. The decrease in size is mostly due to the removal of some
+graphical tools (which were only quick hacks anyway). But also the
+fact that the mysql code is gone cuts down the size a bit.
+
+Being independent of mysql comes at a cost: The fact that paraslash
+now contains its own database (the object storage layer, osl) increases
+the (stripped) binary size of para_server by ~50K on i386.
+
+- no more restrictions on unique basenames.
+- independent of mysql: The new self-contained object
+ storage layer (osl) replaces the mysql database.
+- New executable para_fsck: Check integrity of osl tables.
+- Lyrics support.
+- Reliable audio file move/rename detection.
+- More portable than ever: Tested on Linux (x86_32, x86_64, sparc64),
+ MacOS (ppc32, x86_32), FreeBSD (x86_32), NetBSD (x86_32) and
+ Solaris (sparc64).
+- the new osl-based audio file selector (afs) replaces the random,
+ the playlist and the mysql selector of paraslash-0.2.x.
+- IPv6 support (thanks to Gerrit Renker).
+- paraslash-0.2.x streams are now called "moods". Writing
+ 0.3.x-mood definitions should be both easier and more
+ powerful than writing 0.2.x-stream definitions.
+- para_krell, para_slider, para_para_sdl_gui, para_dbadm have
+ been removed. The world is a better place without them. However,
+ para_gui is still there.
+- afs tracks audio file selection also in playlist mode.
+- few easy-to-use afs commands replace the many not-so-easy-to-use
+ mysql commands (and are available also in playlist mode).
+- Improved error subsystem.
+- The earth-shaking new logo.
+
+-----------------------------------------
+0.2.17 (2007-11-20) "isotropic threshold"
+-----------------------------------------
+
+Mainly bugfixes and cleanups in this version which marks the end of
+the 0.2.x series if no serious bugs show up after the release.
+
+- mysql_selector: fix a locking bug.
+- universal chunk queueing.
+- dccp sender uses chunk queueing if write() returns EAGAIN (thanks
+ to Gerrit Renker).
+- be more carful wrt. signed vs. unsigned argument passing.
+- cleanup error.h and fix some references to invalid error
+ codes.
+- update to gengetopt-2.21.
+- update to ortp-0.13.1.
+- autoconf: extend checks for headers, library functions and
+ compiler characteristics.
+- Fix streaming of large mp3 files.
+- Fix an off-by-one bug in playlist handling.
+
+--------------------------------------
+0.2.16 (2007-04-05) "neural discharge"
+--------------------------------------
+
+The main change in this release is the major audio format handler
+cleanup which removes some similar/duplicate code and makes it easier
+to implement plugins for other audio formats. Of course, the usual mix
+of other improvements/changes/bugfixes also made it into the release.
+
+- simplified audio format handlers (most of the handling functions
+ were moved one layer up to the virtual streaming system).
+- para_server uses mmap to read audio files
+- repositioning of mp3 streams is much faster, in particular for
+ jumping near the end of large mp3 files.
+- permission flags DB_READ,DB_WRITE have been renamed to AFS_READ
+ and AFS_WRITE.
+- fix a bug in para_filter that caused decoding of aac files
+ to start only after a few seconds.
+- fix osx_writer hangs
+- simplified dccp code (thanks to Gerrit Renker)
+- the compress filter works also on big endian systems (ppc)
+
+-----------------------------------------
+0.2.15 (2007-02-16) "inductive resonance"
+-----------------------------------------
+
+Minor improvements, more documentation and a bunch of bug fixes.
+
+- para_server: The server.users file is only read once on server
+ startup rather than for each connection
+- mp3dec: Fix decoding of corrupt mp3 files
+- afs (audio file sender) is now called vss (virtual streaming
+ system). Consequently, the permission flags specified in
+ ~/.paraslash/server.users have also changed: AFS_READ and AFS_WRITE
+ become VSS_READ and VSS_WRITE respectively.
+- para_audiod/para_filter: Fix a bug that caused the last chunk
+ of audio data not being written under certain circumstances
+- audiod: compute the difference of server time and local time
+ correctly
+- para_server/para_audiod: Fix some memory leaks
+- documentation improvements
+- configure.ac: fix checks for para_krell
+- new man pages
+
+-------------------------------------------
+0.2.14 (2006-10-15) "transient singularity"
+-------------------------------------------
+
+The only major enhancement of this version is the osx writer which completes
+the Mac OS Port and was originally planned already for 0.2.13 but had to wait
+until now for reasons beyond the scope of this changelog entry.
+
+- new output plugin for Mac Os: the osx writer
+- rename configure command line options from --enable-xxx-headers to
+ --with-xxx-headers and --enable-xxx-libs to --with-xxx-libs
+- configure: new command line options: --with-mad-headers,
+ --with-mad-libs, --with-oggvorbis-headers, and --with-oggvorbis-libs
+- some robustness fixes
+- dymamic audio format recognition for audiod
+- para_server: new command line option: --autoplay_delay
+- para_audiod: new command line option: --clock_diff_count
+
+---------------------------------------
+0.2.13 (2006-07-14) "sonic convolution"
+---------------------------------------
+
+A bunch of new features and core changes.
+
+- the new paraslash scheduler, short and sweet.
+- Support for m4a/mp4 files via the new aac audio format
+ handler/filter (requires libfaad).
+- each writer has its own command line parser, just like
+ para_recv and para_filter.
+- para_client and para_audioc use the error subsystem
+- writers are integrated in para_audiod (currently linux-only)
+- para_client is integrated in para_audiod
+- random/playlist selector: improved info strings
+- new audiod commands: tasks, kill
+- update to libortp-0.10.1
+- para_fade: wake time defaults to 8 hours from now
+- update to autoconf-2.60
+
+------------------------------------------
+0.2.12 (2006-05-12) "oriented abstraction"
+------------------------------------------
+
+Many user-visible changes in this release and lots of new
+features:
+
+- the new optional dccp sender/receiver. It uses the datagram
+ congestion control protocol. You'll need a fairly new kernel
+ for this.
+- paraslash works on Mac OS X (thanks to Gerd Becker)
+- para_play renamed to para_write
+- modular output plugin design (writers) for para_write
+- new file_writer output plugin for para_write
+- compress filter speed improvements
+- update to libortp-0.9.1
+- update to gengetopt-2.17rc
+- para_client no longer depends on libreadline (as the
+ code for the interactive mode was removed).
+- gcc-2-95 is no longer a supported compiler. It may still
+ work, but it gets no more testing.
+- the tarball no longer contains the screenshot images which
+ reduces its size quite a bit.
+- configure: new command line options: --enable-mysql-headers
+ and --enable-mysql-libs
+
+------------------------------------
+0.2.11 (2006-03-11) "atomic duality"
+------------------------------------
+
+Here it is, the first paraslash release developed with git. There
+are fairly many user-visible changes in this release. As two out of
+the three "database tools" of paraslash don't use a database at all,
+they are now called "audio file selectors" instead.
+
+- the cdt command (change database tool) becomes chs (change
+ selector)
+- no more colon separators: The syntax of some options of
+ para_audiod and para_filter have changed. Use --help for
+ more info (and some examples).
+- update to gengetopt-2.16 (thanks to Lorenzo Bettini)
+- switch from cvs to git (should've done that earlier)
+- the new ipc subsystem
+- new audio file selector: playlist
+- para_server: the dopey selector is now called "random",
+ and is the default selector. Use the --selector option to
+ choose another selector at startup, or the chs command to
+ change the selector at runtime.
+- X86_64 fixes (thanks to Steffen Klassert)
+- para_play fixes
+
+--------------------------------------
+0.2.10 (2006-02-17) "cyclic attractor"
+--------------------------------------
+
+Huge documentation update, a scrollable window for para_gui, ortp
+improvements, and of course many small fixes not mentioned here.
+The diffstat below is rather misleading as most insertions are due
+to the new source documentation.
+
+- autoconf cleanup
+- para_server also uses the new error subsystem
+- lots of new documentation (UTSL)
+- gui improvements:
+ - keysyms for cursor keys and for next/previous page keys
+ - scrollable output window
+ - new internal commands: scroll up/down, page up/down
+ - fix color of command output.
+- ortp: the --chunk_time and --header flags are no longer needed
+for para_recv/para_audiod as this information is now encoded in
+each rtp packet sent by para_server.
+
+-------------------------------------------
+0.2.9 (2006-01-24) "progressive turbulence"
+-------------------------------------------
+
+Internal audiod receivers/filters, the new error subsystem and
+a lot of small improvements.
+
+- para_recv and para_filter are integrated into the para_audiod
+ binary, i.e. audiod no longer spawns a new process for
+ each receiver/filter. As para_recv and para_filter might be
+ useful as standalone programs, they still get built (linked
+ against the same object files that are also used for audiod).
+- further ortp timing improvements should reduce the CPU usage
+ of the ortp receiver.
+- improved audio grabbing. The 'grab' command of para_audiod
+ has its own set of command line options. Read the output of
+ "para_audioc help grab" for more info.
+- oggdec: configurable input prebuffer size.
+- the new error subsystem gives better error diagnostics
+ and reduces code size.
+
+-----------------------------------------
+0.2.8 (2006-01-02) "dynamic accumulation"
+-----------------------------------------
+
+The new modular filter design and the para_play-hangs bugfix.
+
+- new executable: para_filter. It combines para_mp3dec,
+ para_oggdec and para_compress. It also adds a further filter
+ type, wav, that just inserts a wave header at the desired point
+ of the filter chain. All 'piping' is done in-memory (i.e. no
+ read/write operations are used).
+- para_play: fix a stupid bug that caused it to hang under
+ certain circumstances.
+
+-------------------------------------------
+0.2.7 (2006-12-27) "transparent invariance"
+-------------------------------------------
+
+Not many user-visible changes but a fair amount of internal improvements.
+
+- The http sender buffers data if it can not be sent
+ out immediately (because the socket is not writable). This
+ should prevent para_server from shutting down the connection
+ too early on a loaded network.
+- para_play also prebuffers data if it is told to start at a
+ future time by the --start_time option.
+- The return of para_recv: It combines para_ortp_recv and
+ para_http_recv. Use the --receiver option to switch between
+ the two. para_recv builds without libortp, but contains
+ only the http receiver in this case.
+- update to ortp 0.8.1. As this ortp release contains incompatible
+ changes, para_recv-0.2.7 won't link against older ortp libs.
+- improved ortp timings.
+- use of gcc-extensions that #define away for non-gcc and
+ gcc < 3.0.
+
+-------------------------------------------
+0.2.6 (2005-10-29) "recursive compensation"
+-------------------------------------------
+
+Transparent session encryption (uses openssl's Alleged RC4 cipher),
+the internal find command and several other improvements and cleanups.
+
+- Encrypt the session if encryption is requested by the client
+ (default for para_client 0.2.6). This is backwards
+ compatible, so older clients can still connect to para_server
+ 0.2.6. Use the new client option --plain to request an
+ uncrypted session (off by default, must be set to on in
+ order to connect to para_server 0.2.x with 0 <= x <= 5).
+- para_server uses an internal function to locate audio files
+ rather than calling find(1). The server option
+ --mysql_audio_file_dir replaces --mysql_find_cmd.
+- documentation update
+- man pages
+- header file cleanup
+- para_client code cleanup
+- para_gui: faster display of output of display commands
+
+------------------------------------------
+0.2.5 (2005-10-13) "aggressive resolution"
+------------------------------------------
+
+This release adds internal senders, i.e. no more external programs are
+spawned for sending out the audio data. There are two different senders
+available: The http sender and the ortp sender (former para_send which
+is no longer needed).
+
+The new sender code has a plugin-like design so it can be easily
+extended should there be be any future need for supporting another
+network streaming protocol. All senders are completely independent of
+each other. In particular, the http and the ortp sender can operate
+in parallel.
+
+- new server command: sender to control senders at runtime.
+ Read the output of "para_server -h" and "para_client help
+ sender" for more information.
+- para_recv renamed to para_ortp_recv
+- new executable: para_http_recv, a simple command line
+ http receiver.
+- major afs/mp3/ogg code simplifications due to internal
+ senders.
+- ogg timing improvements
+- fix several minor memory leaks (found by valgrind)
+- empty stream definitions work again
+- com_ne(): ignore errors on remove
+- audiod: fix segfault on server restart
+
+---------------------------------------
+0.2.4 (2005-09-21) "toxic anticipation"
+---------------------------------------
+
+Several small improvements, fixes and the new grab command.
+
+- audiod:
+ - new command: "grab" to grab the output of the stream reader
+ or any filters. Read the output of "para_audioc help grab"
+ for more information.
+ - fix memory leak
+ - code cleanup
+- audioc: new command line option: --bufsize to specify a
+ buffer size different from the default size 8192.
+- improved error diagnostics for para_play.
+- new configure option: --enable-ssldir so search for openssl in
+ non-standard places
+- sdl_gui: Make it look nice again for 1024x768
+- server: report total size of memory allocated with sbrk by malloc,
+ new command line option: --announce_time
+
+-----------------------------------------
+0.2.3 (2005-09-01) "hydrophilic movement"
+-----------------------------------------
+
+Two new executables and major feature enhancements.
+
+- audiod filters: It is now possible to specify arbitrary many
+ (including none) filters for each supported audio
+ format. This can be used e.g. for normalizing volume,
+ transforming or grabbing the audio stream, or for using
+ visualizers. Read the output of "para_audiod -h" for the
+ syntax of the new --filter_cmd option.
+- new executable: para_play, a tiny alsa player. It
+ can play wave files or raw pcm (16 bit little endian)
+ from stdin.
+- new executable: para_compress, a dynamic range compressor
+ intended to keep audio output at a consistent volume. Derived
+ from [AudioCompress](http://trikuare.cx/code/AudioCompress.html).
+- audiod: New option: --stream_delay. This can be used in
+ a local network to syncronize the audio output of all
+ clients that play the same stream.
+
+------------------------------------------
+0.2.2 (2005-08-19) "tangential excitation"
+------------------------------------------
+
+Mostly internal changes in this release, but also some new commands
+for the mysql database tool.
+
+- cleanup exec.c, fix para_exec bug
+- compile time loglevel (log messages below the given level
+ won't be compiled in, which reduces the size of the
+ resulting binaries)
+- new log macros that shorten the size of the source code.
+- workaround a gcc-4.1 bug (?) that caused send_cred_buffer()
+ to send only zeros. With this workaround, para_audioc works
+ again.
+- avoid gcc-4 warning: conflicting types for built-in function 'clog'
+- new mysql commands: "rm" (remove entry), "mv" (rename entry) "ne"
+ (new entry), "snp" (set numplayed). Read the manual for more
+ information.
+
+---------------------------------------
+0.2.1 (2005-08-15) "surreal experience"
+---------------------------------------
+
+Here comes paraslash-0.2.1. It contains a couple of new features and,
+surprise, only minor bug fixes.
+
+- kill noisy mp3 debug message
+- cleanup of the build system
+- para_server and para_client directly use the crypto routines
+ of the openssl library rather than invoking the openssl command
+ line utitlity
+- server/audiod: new option --user to switch to the given user
+ when invoked as root. Read the output of "para_server -h" for
+ more information.
+- gui/sdl_gui: new option --stat_cmd to be used to retrieve the
+ status. Default: "para_audioc stat"
+- sdl_gui: new option --pic_cmd to be used to download the picture.
+ Default: "para_client pic"
+- audiod: 5 slots ought to be enough for everybody
+- audiod: new status item: Uptime, kill hup command
+
+------------------------------------------
+0.2.0 (2005-08-06) "distributed diffusion"
+------------------------------------------
+
+After several month of increased development activity, paraslash-0.2.0
+has arrived. It contains many new features and is much more
+self-contained than the old 0.1.x series. Enjoy!
+
+- para_server: fix hang on song change and crash on sighup.
+ Speed up mysql queries. The DIR_LIKE macro is gone.
+- new executables: para_audiod, the local audio daemon that
+ starts playback (uses SCM_CREDENTIALS socket magic) and
+ para_audioc, the corresponding client.
+- new executables: para_mp3dec/para_oggdec, two really teensy
+ decoders. para_mp3dec is based on libmad, para_oggdec requires
+ libvorbisfile.
+- ovsend/ovrecv are capable of streaming ogg as well as mp3, so
+ they are now called para_send and para_recv respectively.
+- documentation updates
+- para_gui is themable. For now there is the default theme that
+ looks as before and the simple theme: blue and easy.
+- gui: audio streaming is now handled by audiod. Time display shows
+ playback time rather than streaming time
+- slider: update to libzmw-0.2.0
+- para_krell: fix crash on server shutdown
+- switch from gzip to bzip2
+
+----------------------------------------
+0.1.7 (2005-04-18) "melting penetration"
+----------------------------------------
+
+The main change in this release is clearly the oggvorbis rewrite,
+but there are also lots of smaller changes. If you intend to use both
+the mp3 and the ogg plugin, it is recommended to use software mixing,
+e.g. the dmix plugin which is provided by ALSA.
+
+- new executables: para_ovsend and para_ovrecv for sending/receiving
+ oggvorbis files via rtp. Requires the open rtp library. Get it at
+ http://www.linphone.org/ortp/
+- rewrite of the ogg_vorbis core code
+- configure detects libzmw and, if detected, includes
+ para_slider to the list of binaries to be built by make
+- server stream writers read from their associated fifo rather
+ than from stdin
+- slider: two new sliders, lastplayed and numplayed
+- fix nasty double free bug which caused random segfaults in case of
+ mp3 files with invalid header information
+- gui: new command line option: --stream_timeout=seconds to
+ deactivate a slot if it is idle for that many seconds (default=`5')
+- diffstats
+
+---------------------------------------
+0.1.6 (2005-03-05) "asymptotic balance"
+---------------------------------------
+
+Only little user-visible changes in this release. Mainly bugfixes and
+core code cleanup. This is probably the most stable version ever if you
+stick to mp3...
+
+- fix several memory leaks
+- rename default name of mysql database from "music" to "paraslash".
+ Use para_server's --mysql_database option if you do not want to
+ rename your old database.
+- rework ogg vorbis code
+- make update command work on mysql servers with LOCAL_INFILE
+ disabled
+- gui: improved stream I/O (slots)
+- simplified audio format API
+- para_pob_ogg is gone
+
+------------------------------------
+0.1.5 (2004-12-31) "opaque eternity"
+------------------------------------
+
+Let's slide gently into the new year.
+
+- new: para_slider (not built automatically, type "make
+ para_slider" to build). A toy for those who always felt that
+ creating stream definitions is difficult. See screenshots,
+ README and FEATURES for more info.
+- improved signal handling. Fixes server segfault on SIGHUP
+ for linux kernels newer than Aug 24 2004 and makes para_gui
+ race-free.
+- reload database tool on SIGHUP
+- improved help message for sl
+- do not log "broken pipe" messages as errors. They are
+ perfectly ok.
+- fix wrong error message on permission errors
+
+-----------------------------------------
+0.1.4 (2004-12-19) "tunneling transition"
+-----------------------------------------
+
+Bugfix release. As expected, 0.1.3 introduced a bunch of new bugs.
+Hopefully, most of them got wiped out with this release. Some
+enhancements went also in.
+
+- improved error diagnostics for all commands
+- stradd/picadd: overwrite previous contents if entry already
+ exists, rather than returning errors
+- stradd: use current stream if invoked without args
+- faster (and hopefully more stable) ogg-vorbis handling
+- para_krell: reap children to avoid zombie-flooding in case
+ no server is running
+- si: report also server pid
+- server: don't busy-loop if dbtool reports only invalid files.
+- gui: CTRL+C works again, fix stream_read command line option
+- fix pic_add, hist
+- fix mysql dbtool startup in case no database exists
+- many small fixes and cleanups
+
+---------------------------------------
+0.1.3: (2004-12-10) "vanishing inertia"
+---------------------------------------
+
+Starting from this release, the database tools are integrated in the
+server binary. This decreases server startup time, reduces code size
+and speeds up database commands. However, the layout of the underlying
+mysql database changed only slightly and 0.1.3 should be backwards
+compatible in that respect.
+
+Visible changes:
+
+- If mysql is not detected at compile time, or fails to init
+ at runtime, fall back to the dopey database tool which should
+ always work.
+- para_dbtool and dbtool.conf are gone. All mysql specific
+ options are read from server.conf and are prefixed by 'mysql_'.
+- new command: cdt (change database tool)
+- new command line option: dbtool (choose startup database tool)
+- The name of current stream is now stored in the database,
+ so paraslash remembers its current stream when restarted.
+- new command: csp (change stream and play)
+- para_gui also reports current database tool and server uptime
+
+-------------------------------------------
+0.1.2: (2004-11-28) "spherical fluctuation"
+-------------------------------------------
+
+Point release before the big dbtool changes go in.
+
+- dbtool: rename ca to cam (copy all meta data). It now also
+ copies numplayed and lastplayed time as well as the picture
+ id.
+- fix endless-loop-bug caused by mp3 files with invalid header
+
+-----------------------------------------
+0.1.1: (2004-11-05) "floating atmosphere"
+-----------------------------------------
+
+- gkrellm plugin
+- new dbtool command: mbox. Browse your sound-file collection
+ with your favorite mail reader.
+- several small fixes
+
+-------------------------------------
+0.1.0: (2004-10-22) "rotating cortex"
+-------------------------------------
+
+- fix logging bug for loglevel > VERBOSE
+- fix skip command
+- correct timings for vbr mp3s
+- modular audio format support
+- ogg-vorbis support (experimental)
+- new server option: autoplay
+
+-----------------------------------------
+0.0.99: (2004-07-25) "harmonic deviation"
+-----------------------------------------
+
+- rename projectname from icc to paraslash (play, archive, rate
+ and stream large audio sets happily)
+- paraslash is no longer restricted to one particular audio
+ streaming software
+- new dbtool commands (stradd, strq, strdel) for easy stream
+ managment w/o configuration file. That obsoletes stream_defs
+ file/config option for dbtool.
+- picadd accepts jpeg data from stdin
+- new server commands: ps (select previous stream), sc (song change)
+- new default pictures for sdl_gui
+- gui: new key_map option for binding commands and internal
+ functions to arbitrary keys, nice help screen, rip out
+ soundcard/linux specific stuff, avoid noise artefacts while jumping,
+ show silly logo on startup
+- new executables: para_fade for fading volume, para_dbadm for
+ manipulating attributes
+- cdb adds _all_ tables to mysql database
+- revised and beautified documentation
+- sample dbtool rewritten in C
+- autoconf
+
+---------------------------------------------
+0.0.98: (2003-12-26) "incremental smoothness"
+---------------------------------------------
+
+- kick icecast in favour of poc. That removes some races and reduces
+ core code considerably.
+- cbr/vbr is displayed by stat and gui/sdl_gui. New status flags
+ give finer info on afs' status.
+- gui can start decoder (see config options). Further new gui
+ commands: refresh (^L), jmp (F1-F10)
+- gui rereads conf on SIGUSR1 instead of SIGHUP. SIGHUP
+ terminates gui. This fixes dead instances consuming memory
+ continuously.
+- new dbtool command: verb for sending verbatim sql queries.
+- fix pid_list races (by removing pid_list)
+- codename funnies
+
+--------------------
+0.0.97: (2003-10-26)
+--------------------
+
+- installation prefix now defaults to /usr/local
+- new commands for gui: snozze, sleep and reread config
+- config file for gui and sdl_gui
+- fix problems with filenames containing funny characters
+ (reported by Thomas Forell)
+- improved signal handling for gui, now it rereads conf on SIGHUP
+- new dbtool command: cdb (create database)
+- switch from argtable to gengetopt
+- major code cleanup and speed improvements
+- fix several potential buffer overflows
+- many small fixes and cleanups
+
+-------------------
+0.0.96 (2003-08-30)
+-------------------
+
+- easy stream_defs syntax
+- sdl_gui can display images associated to the file being played
+- Major feature enhancements for icc_gui including dynamic text
+ placement and the top/bottom window design
+- vrfy/clean now also checks for NULL values in attributes as
+ well as for invalid picture pointers
+- fix long outstanding case sensitivity bug
+- many small fixes and cleanups
+
+-------------------
+0.0.95 (2003-06-29)
+-------------------
+
+- sdl gui runs much faster
+- new dbtool command: ca (copy attributes)
+- count and display number of times the song has been played
+- new feature: scoring
+- command line options for sdl_gui
+- simpler syntax of streams file
+- decrease network traffic of stat
+- fix zombie bug
+- many small fixes and cleanups
+
+-------------------
+0.0.94 (2003-05-04)
+-------------------
+
+- new server command: ns (next stream)
+- new icc_gui command: c (change stream)
+- internal mp3info
+- stat shows also id3 tag info
+- new sdl based gui
+- log flodding bug fixed
+- many small fixes and cleanups
+
+-------------------
+0.0.93 (2003-03-28)
+-------------------
+
+- colors for icc_gui
+- icc_gui sets volume directly (linux only)
+- proper locking that fixes some races
+- fix security bug that caused commands to be executed even
+ with unsufficient permissions
+- new command: hup to make all servers reread their configuration file
+- icecast meta data streaming
+- many small fixes and cleanups
+++ /dev/null
-dnl To generate the html version, execute
-dnl m4 web/manual.m4 | grutatxt --toc
-
-define(`LOCAL_LINK_NAME', `translit(`$1', `A-Z
-', `a-z__')')
-define(`REMOVE_NEWLINE', `translit(`$1',`
-', ` ')')
-
-define(`REFERENCE', ./``#''`LOCAL_LINK_NAME($1)' (`REMOVE_NEWLINE($2)'))
-define(`XREFERENCE', `$1' (`REMOVE_NEWLINE($2)'))
-define(`EMPH', ``_''`REMOVE_NEWLINE($1)'``_'')
-
-Paraslash user manual
-=====================
-
-This document describes how to install, configure and use the paraslash
-network audio streaming system. Most chapters start with a chapter
-overview and conclude with an example section. We try to focus on
-general concepts and on the interaction of the various pieces of the
-paraslash package. Hence this user manual is not meant as a replacement
-for the manual pages that describe all command line options of each
-paraslash executable.
-
-------------
-Introduction
-------------
-
-In this chapter we give an REFERENCE(Overview, overview) of the
-interactions of the two main programs contained in the paraslash
-package, followed by REFERENCE(The paraslash executables, brief
-descriptions) of all executables.
-
-Overview
-~~~~~~~~
-
-The core functionality of the para suite is provided by two main
-executables, para_server and para_audiod. The former maintains a
-database of audio files and streams these files to para_audiod which
-receives and plays the stream.
-
-In a typical setting, both para_server and para_audiod act as
-background daemons whose functionality is controlled by client
-programs: the para_audioc client controls para_audiod over a local
-socket while the para_client program connects to para_server over a
-local or remote networking connection.
-
-Typically, these two daemons run on different hosts but a local setup
-is also possible.
-
-A simplified picture of a typical setup is as follows
-<<
-<pre>
- server_host client_host
- ~~~~~~~~~~~ ~~~~~~~~~~~
-
- +-----------+ audio stream +-----------+
- |para_server| -----------------------------> |para_audiod|
- +-----------+ +-----------+
- ^ ^
- | |
- | | connect
- | |
- | |
- | +-----------+
- | |para_audioc|
- | +-----------+
- |
- |
- | connect +-----------+
- +-------------------------------------- |para_client|
- +-----------+
-</pre>
->>
-
-The paraslash executables
-~~~~~~~~~~~~~~~~~~~~~~~~~
-
-*para_server*
-
-para_server streams binary audio data (MP3, ...) over local and/or
-remote networks. It listens on a TCP port and accepts commands such
-as play, stop, pause, next from authenticated clients. There are
-many more commands though, see the man page of para_server for a
-description of all commands.
-
-It supports three built-in network streaming protocols
-(senders/receivers): HTTP, DCCP, or UDP. This is explained in more
-detail in the section on REFERENCE(Networking, networking).
-
-The built-in audio file selector of paraslash is used to manage your
-audio files. It maintains statistics on the usage of all available
-audio files such as last-played time, and the number of times each
-file was selected.
-
-Additional information may be added to the database to allow
-fine-grained selection based on various properties of the audio file,
-including information found in (ID3) tags. However, old-fashioned
-playlists are also supported.
-
-It is also possible to store images (album covers) and lyrics in the
-database and associate these to the corresponding audio files.
-
-The section on the REFERENCE(The audio file selector, audio file
-selector) discusses this topic.
-
-
-*para_client*
-
-The client program to connect to para_server. paraslash commands
-are sent to para_server and the response is dumped to STDOUT. This
-can be used by any scripting language to produce user interfaces with
-little programming effort.
-
-All connections between para_server and para_client are encrypted
-with a symmetric session key. For each user of paraslash you must
-create a public/secret RSA key pair for authentication.
-
-If para_client is started without non-option arguments, an interactive
-session (shell) is started. Command history and command completion are
-supported through libreadline.
-
-*para_audiod*
-
-The local daemon that collects information from para_server.
-
-It runs on the client side and connects to para_server. As soon as
-para_server announces the availability of an audio stream, para_audiod
-starts an appropriate receiver, any number of filters and a paraslash
-writer to play the stream.
-
-Moreover, para_audiod listens on a local socket and sends status
-information about para_server and para_audiod to local clients on
-request. Access via this local socket may be restricted by using Unix
-socket credentials, if available.
-
-
-*para_audioc*
-
-The client program which talks to para_audiod. Used to control
-para_audiod, to receive status info, or to grab the stream at any
-point of the decoding process. Like para_client, para_audioc supports
-interactive sessions on systems with libreadline.
-
-*para_recv*
-
-A command line HTTP/DCCP/UDP stream grabber. The http mode is
-compatible with arbitrary HTTP streaming sources (e.g. icecast).
-In addition to the three network streaming modes, para_recv can also
-operate in local (afh) mode. In this mode it writes the content of
-an audio file on the local file system in complete chunks to stdout,
-optionally 'just in time'. This allows to cut an audio file without
-first decoding it, and it enables third-party software which is unaware
-of the particular audio format to send complete frames in real time.
-
-*para_filter*
-
-A filter program that reads from STDIN and writes to STDOUT.
-Like para_recv, this is an atomic building block which can be used to
-assemble higher-level audio receiving facilities. It combines several
-different functionalities in one tool: decoders for multiple audio
-formats and a number of processing filters, among these a normalizer
-for audio volume.
-
-*para_afh*
-
-A small stand-alone program that prints tech info about the given
-audio file to STDOUT. It can be instructed to print a "chunk table",
-an array of offsets within the audio file.
-
-*para_write*
-
-A modular audio stream writer. It supports a simple file writer
-output plug-in and optional WAV/raw players for ALSA (Linux) and for
-coreaudio (Mac OS). para_write can also be used as a stand-alone WAV
-or raw audio player.
-
-*para_play*
-
-A command line audio player.
-
-*para_gui*
-
-Curses-based gui that presents status information obtained in a curses
-window. Appearance can be customized via themes. para_gui provides
-key-bindings for the most common server commands and new key-bindings
-can be added easily.
-
-
-*para_fade*
-
-An alarm clock and volume-fader for OSS and ALSA.
-
------------
-Quick start
------------
-
-This chapter lists the REFERENCE(Requirements, necessary software)
-that must be installed to compile the paraslash package, describes
-how to REFERENCE(Installation, compile and install) the paraslash
-source code and the steps that have to be performed in order to
-REFERENCE(Quick start, set up) a typical server and client.
-
-Requirements
-~~~~~~~~~~~~
-For the impatient:
-
- git clone git://git.tuebingen.mpg.de/osl
- cd osl && make && sudo make install && sudo ldconfig
- sudo apt-get install autoconf libssl-dev help2man gengetopt \
- libmad0-dev libid3tag0-dev libasound2-dev libvorbis-dev \
- libfaad-dev libspeex-dev libFLAC-dev libsamplerate-dev \
- libasound2-dev libao-dev libreadline-dev libncurses-dev \
- libopus-dev
-
-Detailed description: In any case you'll need
-
- - XREFERENCE(http://people.tuebingen.mpg.de/maan/osl/, libosl).
- The _object storage layer_ library is used by para_server. To
- clone the source code repository, execute
-
- git clone git://git.tuebingen.mpg.de/osl
-
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/gcc, gcc) or
- XREFERENCE(http://clang.llvm.org, clang). All gcc versions
- >= 3.3 are currently supported. Clang version 1.1 or newer
- should work as well.
-
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/make, gnu make) is
- also shipped with the disto. On BSD systems the gnu make
- executable is often called gmake.
-
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/bash, bash). Some
- scripts which run during compilation require the EMPH(Bourne
- again shell). It is most likely already installed.
-
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/gengetopt/, gengetopt)
- is needed to generate the C code for the command line parsers
- of all paraslash executables.
-
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/help2man, help2man)
- is used to create the man pages.
-
-Optional:
-
- - XREFERENCE(http://www.openssl.org/, openssl) or
- XREFERENCE(ftp://ftp.gnupg.org/gcrypt/libgcrypt/, libgcrypt).
- At least one of these two libraries is needed as the backend
- for cryptographic routines on both the server and the client
- side. Both openssl and libgcrypt are usually shipped with the
- distro, but you might have to install the development package
- (libssl-dev or libgcrypt-dev on debian systems) as well.
-
- - XREFERENCE(http://www.underbit.com/products/mad/, libmad).
- To compile in MP3 support for paraslash, the development
- package must be installed. It is called libmad0-dev on
- debian-based systems. Note that libmad is not necessary on
- the server side, i.e. for sending MP3 files.
-
- - XREFERENCE(http://www.underbit.com/products/mad/,
- libid3tag). For version-2 ID3 tag support, you'll need
- the libid3tag development package libid3tag0-dev. Without
- libid3tag, only version-1 tags are recognized. The mp3 tagger
- also needs this library for modifying (id3v1 and id3v2) tags.
-
- - XREFERENCE(http://www.xiph.org/downloads/, ogg vorbis).
- For ogg vorbis streams you'll need libogg, libvorbis,
- libvorbisfile. The corresponding Debian packages are called
- libogg-dev and libvorbis-dev.
-
- - XREFERENCE(http://www.audiocoding.com/, libfaad). For aac
- files (m4a) you'll need libfaad (libfaad-dev).
-
- - XREFERENCE(http://www.speex.org/, speex). In order to stream
- or decode speex files, libspeex (libspeex-dev) is required.
-
- - XREFERENCE(http://flac.sourceforge.net/, flac). To stream
- or decode files encoded with the _Free Lossless Audio Codec_,
- libFLAC (libFLAC-dev) must be installed.
-
- - XREFERENCE(http://www.mega-nerd.com/SRC/index.html,
- libsamplerate). The resample filter will only be compiled if
- this library is installed. Debian package: libsamplerate-dev.
-
- - XREFERENCE(ftp://ftp.alsa-project.org/pub/lib/, alsa-lib). On
- Linux, you'll need to have ALSA's development package
- libasound2-dev installed.
-
- - XREFERENCE(http://downloads.xiph.org/releases/ao/,
- libao). Needed to build the ao writer (ESD, PulseAudio,...).
- Debian package: libao-dev.
-
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/ncurses, curses). Needed
- for para_gui. Debian package: libncurses-dev.
-
- - XREFERENCE(http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html,
- GNU Readline). If this library (libreadline-dev) is installed,
- para_client, para_audioc and para_play support interactive
- sessions.
-
-Installation
-~~~~~~~~~~~~
-To build the sources from a tarball, execute
-
- ./configure && make
-
-To build from git or a gitweb snapshot, run this command instead:
-
- ./autogen.sh
-
-There should be no errors but probably some warnings about missing
-packages which usually implies that not all audio formats will be
-supported. If headers or libs are installed at unusual locations you
-might need to tell the configure script where to find them. Try
-
- ./configure --help
-
-to see a list of options. If the paraslash package was compiled
-successfully, execute (optionally)
-
- make test
-
-to run the paraslash test suite. If all tests pass, execute as root
-
- make install
-
-to install executables under /usr/local/bin and the man pages under
-/usr/local/man.
-
-Configuration
-~~~~~~~~~~~~~
-
-*Step 1*: Create a paraslash user
-
-In order to control para_server at runtime you must create a paraslash
-user. As authentication is based on the RSA crypto system you'll have
-to create an RSA key pair. If you already have a user and an RSA key
-pair, you may skip this step.
-
-In this section we'll assume a typical setup: You would like to run
-para_server on some host called server_host as user foo, and you want
-to connect to para_server from another machine called client_host as
-user bar.
-
-As foo@server_host, create ~/.paraslash/server.users by typing the
-following commands:
-
- user=bar
- target=~/.paraslash/server.users
- key=~/.paraslash/id_rsa.pub.$user
- perms=AFS_READ,AFS_WRITE,VSS_READ,VSS_WRITE
- mkdir -p ~/.paraslash
- echo "user $user $key $perms" >> $target
-
-Next, change to the "bar" account on client_host and generate the
-key pair with the commands
-
- ssh-keygen -q -t rsa -b 2048 -N '' -f $key
-
-This generates the two files id_rsa and id_rsa.pub in ~/.ssh. Note
-that para_server won't accept keys shorter than 2048 bits. Moreover,
-para_client rejects private keys which are world-readable.
-
-para_server only needs to know the public key of the key pair just
-created. Copy this public key to server_host:
-
- src=~/.ssh/id_rsa.pub
- dest=.paraslash/id_rsa.pub.$LOGNAME
- scp $src foo@server_host:$dest
-
-Finally, tell para_client to connect to server_host:
-
- conf=~/.paraslash/client.conf
- echo 'hostname server_host' > $conf
-
-
-*Step 2*: Start para_server
-
-For this first try, we'll use the info loglevel to make the output
-of para_server more verbose.
-
- para_server -l info
-
-Now you can use para_client to connect to the server and issue
-commands. Open a new shell as bar@client_host and try
-
- para_client help
- para_client si
-
-to retrieve the list of available commands and some server info.
-Don't proceed if this doesn't work.
-
-*Step 3*: Create and populate the database
-
-An empty database is created with
-
- para_client init
-
-This initializes a couple of empty tables under
-~/.paraslash/afs_database-0.4. You normally don't need to look at these
-tables, but it's good to know that you can start from scratch with
-
- rm -rf ~/.paraslash/afs_database-0.4
-
-in case something went wrong.
-
-Next, you need to add some audio files to that database so that
-para_server knows about them. Choose an absolute path to a directory
-containing some audio files and add them to the audio file table:
-
- para_client add /my/mp3/dir
-
-This might take a while, so it is a good idea to start with a directory
-containing not too many files. Note that the table only contains data
-about the audio files found, not the files themselves.
-
-You may print the list of all known audio files with
-
- para_client ls
-
-*Step 4*: Configure para_audiod
-
-We will have to tell para_audiod that it should receive the audio
-stream from server_host via http:
-
- para_audiod -l info -r '.:http -i server_host'
-
-You should now be able to listen to the audio stream once para_server
-starts streaming. To activate streaming, execute
-
- para_client play
-
-Since no playlist has been specified yet, the "dummy" mode which
-selects all known audio files is activated automatically. See the
-section on the REFERENCE(The audio file selector, audio file selector)
-for how to use playlists and moods to specify which files should be
-streamed in which order.
-
-*Troubleshooting*
-
-If you receive a socket related error on server or audiod startup,
-make sure you have write permissions to the /var/paraslash directory:
-
- sudo chown $LOGNAME /var/paraslash
-
-Alternatively, use the --afs-socket (para_server) or --socket
-(para_audiod) option to specify a different socket pathname.
-
-To identify streaming problems try to receive, decode and play the
-stream manually using para_recv, para_filter and para_write as follows.
-For simplicity we assume that you're running Linux/ALSA and that only
-MP3 files have been added to the database.
-
- para_recv -r 'http -i server_host' > file.mp3
- # (interrupt with CTRL+C after a few seconds)
- ls -l file.mp3 # should not be empty
- para_filter -f mp3dec -f wav < file.mp3 > file.wav
- ls -l file.wav # should be much bigger than file.mp3
- para_write -w alsa < file.wav
-
-Double check what is logged by para_server and use the --loglevel
-option of para_recv, para_filter and para_write to increase verbosity.
-
----------------
-User management
----------------
-
-para_server uses a challenge-response mechanism to authenticate
-requests from incoming connections, similar to ssh's public key
-authentication method. Authenticated connections are encrypted using
-a stream cipher, either RC4 or AES in integer counter mode.
-
-In this chapter we briefly describe RSA, RC4 and AES, and sketch the
-REFERENCE(Client-server authentication, authentication handshake)
-between para_client and para_server. User management is discussed
-in the section on REFERENCE(The user_list file, the user_list file).
-These sections are all about communication between the client and the
-server. Connecting para_audiod is a different matter and is described
-in a REFERENCE(Connecting para_audiod, separate section).
-
-
-
-RSA, RC4, AES
-~~~~~~~~~~~~~
-
-RSA is an asymmetric block cipher which is used in many applications,
-including ssh and gpg. An RSA key consists in fact of two keys,
-called the public key and the private key. A message can be encrypted
-with either key and only the counterpart of that key can decrypt
-the message. While RSA can be used for both signing and encrypting
-a message, paraslash uses RSA only for the latter purpose. The
-RSA public key encryption and signatures algorithms are defined in
-detail in RFC 2437.
-
-RC4 is a stream cipher, i.e. the input is XORed with a pseudo-random
-key stream to produce the output. Decryption uses the same function
-calls as encryption. While RC4 supports variable key lengths,
-paraslash uses a fixed length of 256 bits, which is considered a
-strong encryption by today's standards. Since the same key must never
-be used twice, a different, randomly-generated key is used for every
-new connection.
-
-AES, the advanced encryption standard, is a well-known symmetric block
-cipher, i.e. a transformation operating on fixed-length blocks which
-is determined by a single key for both encryption and decryption. Any
-block cipher can be turned into a stream cipher by generating
-a pseudo-random key stream by encrypting successive values of a
-counter. The AES_CTR128 stream cipher used in paraslash is obtained
-in this way from the AES block cipher with a 128 bit block size.
-
-
-Client-server authentication
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The authentication handshake between para_client and para_server goes
-as follows:
-
- - para_client connects to para_server and sends an
- authentication request for a user. It does so by connecting
- to TCP port 2990 of the server host. This port is called the
- para_server _control port_.
-
- - para_server accepts the connection and forks a child process
- which handles the incoming request. The parent process keeps
- listening on the control port while the child process (also
- called para_server below) continues as follows.
-
- - para_server loads the RSA public key of that user, fills a
- fixed-length buffer with random bytes, encrypts that buffer
- using the public key and sends the encrypted buffer to the
- client. The first part of the buffer is the challenge which
- is used for authentication while the second part is the
- session key.
-
- - para_client receives the encrypted buffer and decrypts it
- with the user's private key, thereby obtaining the challenge
- buffer and the session key. It sends the SHA1 hash value of
- the challenge back to para_server and stores the session key
- for further use.
-
- - para_server also computes the SHA1 hash of the challenge
- and compares it against what was sent back by the client.
-
- - If the two hashes do not match, the authentication has
- failed and para_server closes the connection.
-
- - Otherwise the user is considered authenticated and the client
- is allowed to proceed by sending a command to be executed. From
- this point on the communication is encrypted using the stream
- cipher with the session key known to both peers.
-
-paraslash relies on the quality of the pseudo-random bytes provided
-by the crypto library (openssl or libgcrypt), on the security of
-the implementation of the RSA, RC4 and AES crypto routines and on the
-infeasibility to invert the SHA1 function.
-
-Neither para_server or para_client create RSA keys on their own. This
-has to be done once for each user as sketched in REFERENCE(Quick start,
-Quick start) and discussed in more detail REFERENCE(The user_list
-file, below).
-
-The user_list file
-~~~~~~~~~~~~~~~~~~
-
-At startup para_server reads the user list file which contains one
-line per user. The default location of the user list file may be
-changed with the --user-list option.
-
-There should be at least one user in this file. Each user must have
-an RSA key pair. The public part of the key is needed by para_server
-while the private key is needed by para_client. Each line of the
-user list file must be of the form
-
- user <username> <key> <perms>
-
-where _username_ is an arbitrary string (usually the user's login
-name), _key_ is the full path to that user's public RSA key, and
-_perms_ is a comma-separated list of zero or more of the following
-permission bits:
-
- +---------------------------------------------------------+
- | AFS_READ | read the contents of the databases |
- +-----------+---------------------------------------------+
- | AFS_WRITE | change database contents |
- +-----------+---------------------------------------------+
- | VSS_READ | obtain information about the current stream |
- +-----------+---------------------------------------------+
- | VSS_WRITE | change the current stream |
- +---------------------------------------------------------+
-
-The permission bits specify which commands the user is allowed to
-execute. The output of
-
- para_client help
-
-contains in the third column the permissions needed to execute the
-command.
-
-It is possible to make para_server reread the user_list file by
-executing the paraslash "hup" command or by sending SIGHUP to the
-PID of para_server.
-
-
-Connecting para_audiod
-~~~~~~~~~~~~~~~~~~~~~~
-
-para_audiod listens on a Unix domain socket. Those sockets are
-for local communication only, so only local users can connect to
-para_audiod. The default is to let any user connect but this can be
-restricted on platforms that support UNIX socket credentials which
-allow para_audiod to obtain the Unix credentials of the connecting
-process.
-
-Use para_audiod's --user-allow option to allow connections only for
-a limited set of users.
-
------------------------
-The audio file selector
------------------------
-
-paraslash comes with a sophisticated audio file selector (AFS),
-whose main task is to determine which file to stream next, based on
-information on the audio files stored in a database. It communicates
-also with para_client whenever an AFS command is executed, for example
-to answer a database query.
-
-Besides the traditional playlists, AFS supports audio file selection
-based on _moods_ which act as a filter that limits the set of all
-known audio files to those which satisfy certain criteria. It also
-maintains tables containing images (e.g. album cover art) and lyrics
-that can be associated with one or more audio files.
-
-AFS uses XREFERENCE(http://people.tuebingen.mpg.de/maan/osl/, libosl), the
-object storage layer library, as the backend library for storing
-information on audio files, playlists, etc. This library offers
-functionality similar to a relational database, but is much more
-lightweight than a full database backend.
-
-In this chapter we sketch the setup of the REFERENCE(The AFS process,
-AFS process) during server startup and proceed with the description
-of the REFERENCE(Database layout, layout) of the various database
-tables. The section on REFERENCE(Playlists and moods, playlists
-and moods) explains these two audio file selection mechanisms
-in detail and contains pratical examples. The way REFERENCE(File
-renames and content changes, file renames and content changes) are
-detected is discussed briefly before the REFERENCE(Troubleshooting,
-Troubleshooting) section concludes the chapter.
-
-The AFS process
-~~~~~~~~~~~~~~~
-
-On startup, para_server forks to create the AFS process which opens
-the OSL database tables. The server process communicates with the
-AFS process via pipes and shared memory. Usually, the AFS process
-awakes only briefly whenever the current audio file changes. The AFS
-process determines the next audio file, opens it, verifies it has
-not been changed since it was added to the database and passes the
-open file descriptor to the server process, along with audio file
-meta-data such as file name, duration, audio format and so on. The
-server process then starts to stream the audio file.
-
-The AFS process also accepts connections from local clients via
-a well-known socket. However, only child processes of para_server
-may connect through this socket. All server commands that have the
-AFS_READ or AFS_WRITE permission bits use this mechanism to query or
-change the database.
-
-Database layout
-~~~~~~~~~~~~~~~
-
-*The audio file table*
-
-This is the most important and usually also the largest table of the
-AFS database. It contains the information needed to stream each audio
-file. In particular the following data is stored for each audio file.
-
- - SHA1 hash value of the audio file contents. This is computed
- once when the file is added to the database. Whenever AFS
- selects this audio file for streaming the hash value is
- recomputed and checked against the value stored in the
- database to detect content changes.
-
- - The time when this audio file was last played.
-
- - The number of times the file has been played so far.
-
- - The attribute bitmask.
-
- - The image id which describes the image associated with this
- audio file.
-
- - The lyrics id which describes the lyrics associated with
- this audio file.
-
- - The audio format id (MP3, OGG, ...).
-
- - An amplification value that can be used by the amplification
- filter to pre-amplify the decoded audio stream.
-
- - The chunk table. It describes the location and the timing
- of the building blocks of the audio file. This is used by
- para_server to send chunks of the file at appropriate times.
-
- - The duration of the audio file.
-
- - Tag information contained in the audio file (ID3 tags,
- Vorbis comments, ...).
-
- - The number of channels
-
- - The encoding bitrate.
-
- - The sampling frequency.
-
-To add or refresh the data contained in the audio file table, the _add_
-command is used. It takes the full path of either an audio file or a
-directory. In the latter case, the directory is traversed recursively
-and all files which are recognized as valid audio files are added to
-the database.
-
-*The attribute table*
-
-The attribute table contains two columns, _name_ and _bitnum_. An
-attribute is simply a name for a certain bit number in the attribute
-bitmask of the audio file table.
-
-Each of the 64 bits of the attribute bitmask can be set for each
-audio file individually. Hence up to 64 different attributes may be
-defined. For example, "pop", "rock", "blues", "jazz", "instrumental",
-"german_lyrics", "speech", whatever. You are free to choose as
-many attributes as you like and there are no naming restrictions
-for attributes.
-
-A new attribute "test" is created by
-
- para_client addatt test
-and
- para_client lsatt
-
-lists all available attributes. You can set the "test" attribute for
-an audio file by executing
-
- para_client setatt test+ /path/to/the/audio/file
-
-Similarly, the "test" bit can be removed from an audio file with
-
- para_client setatt test- /path/to/the/audio/file
-
-Instead of a path you may use a shell wildcard pattern. The attribute
-is applied to all audio files matching this pattern:
-
- para_client setatt test+ '/test/directory/*'
-
-The command
-
- para_client -- ls -l=v
-
-gives you a verbose listing of your audio files also showing which
-attributes are set.
-
-In case you wonder why the double-dash in the above command is needed:
-It tells para_client to not interpret the options after the dashes. If
-you find this annoying, just say
-
- alias para='para_client --'
-
-and be happy. In what follows we shall use this alias.
-
-The "test" attribute can be dropped from the database with
-
- para rmatt test
-
-Read the output of
-
- para help ls
- para help setatt
-
-for more information and a complete list of command line options to
-these commands.
-
-*Blob tables*
-
-The image, lyrics, moods and playlists tables are all blob tables.
-Blob tables consist of three columns each: The identifier which is
-a positive non-negative number that is auto-incremented, the name
-(an arbitrary string) and the content (the blob).
-
-All blob tables support the same set of actions: cat, ls, mv, rm
-and add. Of course, _add_ is used for adding new blobs to the table
-while the other actions have the same meaning as the corresponding
-Unix commands. The paraslash commands to perform these actions are
-constructed as the concatenation of the table name and the action. For
-example addimg, catimg, lsimg, mvimg, rmimg are the commands that
-manipulate or query the image table.
-
-The add variant of these commands is special as these commands read
-the blob contents from stdin. To add an image to the image table the
-command
-
- para addimg image_name < file.jpg
-
-can be used.
-
-Note that the images and lyrics are not interpreted at all, and also
-the playlist and the mood blobs are only investigated when the mood
-or playlist is activated with the select command.
-
-*The score table*
-
-Unlike all other tables the contents of the score table remain in
-memory and are never stored on disk. The score table contains two
-columns: The SHA1 hash value (of an audio file) and its current
-score.
-
-However, only those files which are admissible for the current mood
-or playlist are contained in the score table. The audio file selector
-always chooses the row with the highest score as the file to stream
-next. While doing so, it computes the new score and updates the
-last_played and the num_played fields in the audio file table.
-
-The score table is recomputed by the select command which loads a
-mood or playlist. Audio files are chosen for streaming from the rows
-of the score table on a highest-score-first basis.
-
-
-Playlists and moods
-~~~~~~~~~~~~~~~~~~~
-
-Playlists and moods offer two different ways of specifying the set of
-admissible files. A playlist in itself describes a set of admissible
-files. A mood, in contrast, describes the set of admissible files in
-terms of attributes and other type of information available in the
-audio file table. As an example, a mood can define a filename pattern,
-which is then matched against the names of audio files in the table.
-
-*Playlists*
-
-Playlists are accommodated in the playlist table of the afs database,
-using the aforementioned blob format for tables. A new playlist is
-created with the addpl command by specifying the full (absolute)
-paths of all desired audio files, separated by newlines. Example:
-
- find /my/mp3/dir -name "*.mp3" | para addpl my_playlist
-
-If _my_playlist_ already exists it is overwritten. To activate the
-new playlist, execute
-
- para select p/my_playlist
-
-The audio file selector will assign scores to each entry of the list,
-in descending order so that files will be selected in order. If a
-file could not be opened for streaming, its entry is removed from
-the score table (but not from the playlist).
-
-*Moods*
-
-A mood consists of a unique name and its *mood definition*, which is
-a set of *mood lines* containing expressions in terms of attributes
-and other data contained in the database.
-
-At any time at most one mood can be *active* which means that
-para_server is going to select only files from that subset of
-admissible files.
-
-So in order to create a mood definition one has to write a set of
-mood lines. Mood lines come in three flavours: Accept lines, deny
-lines and score lines.
-
-The general syntax of the three types of mood lines is
-
-
- accept [with score <score>] [if] [not] <mood_method> [options]
- deny [with score <score>] [if] [not] <mood_method> [options]
- score <score> [if] [not] <mood_method> [options]
-
-
-Here <score> is either an integer or the string "random" which assigns
-a random score to all matching files. The score value changes the
-order in which admissible files are going to be selected, but is of
-minor importance for this introduction.
-
-So we concentrate on the first two forms, i.e. accept and deny
-lines. As usual, everything in square brackets is optional, i.e.
-accept/deny lines take the following form when ignoring scores:
-
- accept [if] [not] <mood_method> [options]
-
-and analogously for the deny case. The "if" keyword is only syntactic
-sugar and has no function. The "not" keyword just inverts the result,
-so the essence of a mood line is the mood method part and the options
-following thereafter.
-
-A *mood method* is realized as a function which takes an audio file
-and computes a number from the data contained in the database.
-If this number is non-negative, we say the file *matches* the mood
-method. The file matches the full mood line if it either
-
- - matches the mood method and the "not" keyword is not given,
-or
- - does not match the mood method, but the "not" keyword is given.
-
-The set of admissible files for the whole mood is now defined as those
-files which match at least one accept mood line, but no deny mood line.
-More formally, an audio file F is admissible if and only if
-
- (F ~ AL1 or F ~ AL2...) and not (F ~ DL1 or F ~ DN2 ...)
-
-where AL1, AL2... are the accept lines, DL1, DL2... are the deny
-lines and "~" means "matches".
-
-The cases where no mood lines of accept/deny type are defined need
-special treatment:
-
- - Neither accept nor deny lines: This treats all files as
- admissible (in fact, that is the definition of the dummy mood
- which is activated automatically if no moods are available).
-
- - Only accept lines: A file is admissible iff it matches at
- least one accept line:
-
- F ~ AL1 or F ~ AL2 or ...
-
- - Only deny lines: A file is admissible iff it matches no
- deny line:
-
- not (F ~ DL1 or F ~ DN2 ...)
-
-
-
-*List of mood_methods*
-
- no_attributes_set
-
-Takes no arguments and matches an audio file if and only if no
-attributes are set.
-
- is_set <attribute_name>
-
-Takes the name of an attribute and matches iff that attribute is set.
-
- path_matches <pattern>
-
-Takes a filename pattern and matches iff the path of the audio file
-matches the pattern.
-
- artist_matches <pattern>
- album_matches <pattern>
- title_matches <pattern>
- comment_matches <pattern>
-
-Takes an extended regular expression and matches iff the text of the
-corresponding tag of the audio file matches the pattern. If the tag
-is not set, the empty string is matched against the pattern.
-
- year ~ <num>
- bitrate ~ <num>
- frequency ~ <num>
- channels ~ <num>
- num_played ~ <num>
-
-Takes a comparator ~ of the set {<, =, <=, >, >=, !=} and a number
-<num>. Matches an audio file iff the condition <val> ~ <num> is
-satisfied where val is the corresponding value of the audio file
-(value of the year tag, bitrate in kbit/s, frequency in Hz, channel
-count, play count).
-
-The year tag is special as its value is undefined if the audio file
-has no year tag or the content of the year tag is not a number. Such
-audio files never match. Another difference is the special treatment
-if the year tag is a two-digit number. In this case either 1900 or
-2000 is added to the tag value, depending on whether the number is
-greater than 2000 plus the current year.
-
-
-*Mood usage*
-
-To create a new mood called "my_mood", write its definition into
-some temporary file, say "tmpfile", and add it to the mood table
-by executing
-
- para addmood my_mood < tmpfile
-
-If the mood definition is really short, you may just pipe it to the
-client instead of using temporary files. Like this:
-
- echo "$MOOD_DEFINITION" | para addmood my_mood
-
-There is no need to keep the temporary file since you can always use
-the catmood command to get it back:
-
- para catmood my_mood
-
-A mood can be activated by executing
-
- para select m/my_mood
-
-Once active, the list of admissible files is shown by the ls command
-if the "-a" switch is given:
-
- para ls -a
-
-
-*Example mood definition*
-
-Suppose you have defined attributes "punk" and "rock" and want to define
-a mood containing only Punk-Rock songs. That is, an audio file should be
-admissible if and only if both attributes are set. Since
-
- punk and rock
-
-is obviously the same as
-
- not (not punk or not rock)
-
-(de Morgan's rule), a mood definition that selects only Punk-Rock
-songs is
-
- deny if not is_set punk
- deny if not is_set rock
-
-
-
-File renames and content changes
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Since the audio file selector knows the SHA1 of each audio file that
-has been added to the afs database, it recognizes if the content of
-a file has changed, e.g. because an ID3 tag was added or modified.
-Also, if a file has been renamed or moved to a different location,
-afs will detect that an entry with the same hash value already exists
-in the audio file table.
-
-In both cases it is enough to just re-add the new file. In the
-first case (file content changed), the audio table is updated, while
-metadata such as the num_played and last_played fields, as well as
-the attributes, remain unchanged. In the other case, when the file
-is moved or renamed, only the path information is updated, all other
-data remains as before.
-
-It is possible to change the behaviour of the add command by using the
-"-l" (lazy add) or the "-f" (force add) option.
-
-Troubleshooting
-~~~~~~~~~~~~~~~
-
-Use the debug loglevel (-l debug) to show debugging info. All paraslash
-executables have a brief online help which is displayed when -h is
-given. The --detailed-help option prints the full help text.
-
-If para_server crashed or was killed by SIGKILL (signal 9), it
-may refuse to start again because of "dirty osl tables". In this
-case you'll have to run the oslfsck program of libosl to fix your
-database:
-
- oslfsck -fd ~/.paraslash/afs_database-0.4
-
-However, make sure para_server isn't running before executing oslfsck.
-
-If you don't mind to recreate your database you can start
-from scratch by removing the entire database directory, i.e.
-
- rm -rf ~/.paraslash/afs_database-0.4
-
-Be aware that this removes all attribute definitions, all playlists
-and all mood definitions and requires to re-initialize the tables.
-
-Although oslfsck fixes inconsistencies in database tables it doesn't
-care about the table contents. To check for invalid table contents, use
-
- para_client check
-
-This prints out references to missing audio files as well as invalid
-playlists and mood definitions.
-
-Similarly, para_audiod refuses to start if its socket file exists, since
-this indicates that another instance of para_audiod is running. After
-a crash a stale socket file might remain and you must run
-
- para_audiod --force
-
-once to fix it up.
-
----------------------------------------
-Audio formats and audio format handlers
----------------------------------------
-
-Audio formats
-~~~~~~~~~~~~~
-
-The following audio formats are supported by paraslash:
-
-*MP3*
-
-Mp3, MPEG-1 Audio Layer 3, is a common audio format for audio storage,
-designed as part of its MPEG-1 standard. An MP3 file is made up of
-multiple MP3 frames, which consist of a header and a data block. The
-size of an MP3 frame depends on the bit rate and on the number
-of channels. For a typical CD-audio file (sample rate of 44.1 kHz
-stereo), encoded with a bit rate of 128 kbit, an MP3 frame is about
-400 bytes large.
-
-*OGG/Vorbis*
-
-OGG is a standardized audio container format, while Vorbis is an
-open source codec for lossy audio compression. Since Vorbis is most
-commonly made available via the OGG container format, it is often
-referred to as OGG/Vorbis. The OGG container format divides data into
-chunks called OGG pages. A typical OGG page is about 4KB large. The
-Vorbis codec creates variable-bitrate (VBR) data, where the bitrate
-may vary considerably.
-
-*OGG/Speex*
-
-Speex is an open-source speech codec that is based on CELP (Code
-Excited Linear Prediction) coding. It is designed for voice
-over IP applications, has modest complexity and a small memory
-footprint. Wideband and narrowband (telephone quality) speech are
-supported. As for Vorbis audio, Speex bit-streams are often stored
-in OGG files. As of 2012 this codec is considered obsolete since the
-Oppus codec, described below, surpasses its performance in all areas.
-
-*OGG/Opus*
-
-Opus is a lossy audio compression format standardized through RFC
-6716 in 2012. It combines the speech-oriented SILK codec and the
-low-latency CELT (Constrained Energy Lapped Transform) codec. Like
-OGG/Vorbis and OGG/Speex, Opus data is usually encapsulated in OGG
-containers. All known software patents which cover Opus are licensed
-under royalty-free terms.
-
-*AAC*
-
-Advanced Audio Coding (AAC) is a standardized, lossy compression
-and encoding scheme for digital audio which is the default audio
-format for Apple's iPhone, iPod, iTunes. Usually MPEG-4 is used as
-the container format and audio files encoded with AAC have the .m4a
-extension. A typical AAC frame is about 700 bytes large.
-
-*WMA*
-
-Windows Media Audio (WMA) is an audio data compression technology
-developed by Microsoft. A WMA file is usually encapsulated in the
-Advanced Systems Format (ASF) container format, which also specifies
-how meta data about the file is to be encoded. The bit stream of WMA
-is composed of superframes, each containing one or more frames of
-2048 samples. For 16 bit stereo a WMA superframe is about 8K large.
-
-*FLAC*
-
-The Free Lossless Audio Codec (FLAC) compresses audio without quality
-loss. It gives better compression ratios than a general purpose
-compressor like zip or bzip2 because FLAC is designed specifically
-for audio. A FLAC-encoded file consists of frames of varying size, up
-to 16K. Each frame starts with a header that contains all information
-necessary to decode the frame.
-
-Meta data
-~~~~~~~~~
-
-Unfortunately, each audio format has its own conventions how meta
-data is added as tags to the audio file.
-
-For MP3 files, ID3, version 1 and 2 are widely used. ID3 version 1
-is rather simple but also very limited as it supports only artist,
-title, album, year and comment tags. Each of these can only be at most
-32 characters long. ID3, version 2 is much more flexible but requires
-a separate library being installed for paraslash to support it.
-
-Ogg vorbis, ogg speex and flac files contain meta data as Vorbis
-comments, which are typically implemented as strings of the form
-"[TAG]=[VALUE]". Unlike ID3 version 1 tags, one may use whichever
-tags are appropriate for the content.
-
-AAC files usually use the MPEG-4 container format for storing meta
-data while WMA files wrap meta data as special objects within the
-ASF container format.
-
-paraslash only tracks the most common tags that are supported by
-all tag variants: artist, title, year, album, comment. When a file
-is added to the AFS database, the meta data of the file is extracted
-and stored in the audio file table.
-
-Chunks and chunk tables
-~~~~~~~~~~~~~~~~~~~~~~~
-
-paraslash uses the word "chunk" as common term for the building blocks
-of an audio file. For MP3 files, a chunk is the same as an MP3 frame,
-while for OGG files a chunk is an OGG page, etc. Therefore the chunk
-size varies considerably between audio formats, from a few hundred
-bytes (MP3) up to 16K (FLAC).
-
-The chunk table contains the offsets within the audio file that
-correspond to the chunk boundaries of the file. Like the meta data,
-the chunk table is computed and stored in the database whenever an
-audio file is added.
-
-The paraslash senders (see below) always send complete chunks. The
-granularity for seeking is therefore determined by the chunk size.
-
-Audio format handlers
-~~~~~~~~~~~~~~~~~~~~~
-
-For each audio format paraslash contains an audio format handler whose
-first task is to tell whether a given file is a valid audio file of
-this type. If so, the audio file handler extracts some technical data
-(duration, sampling rate, number of channels etc.), computes the
-chunk table and reads the meta data.
-
-The audio format handler code is linked into para_server and executed
-via the _add_ command. The same code is also available as a stand-alone
-tool, para_afh, which prints the technical data, the chunk table
-and the meta data of a file. Moreover, all audio format handlers are
-combined in the afh receiver which is part of para_recv and para_play.
-
-----------
-Networking
-----------
-
-Paraslash uses different network connections for control and data.
-para_client communicates with para_server over a dedicated TCP control
-connection. To transport audio data, separate data connections are
-used. For these data connections, a variety of transports (UDP, DCCP,
-HTTP) can be chosen.
-
-The chapter starts with the REFERENCE(The paraslash control
-service, control service), followed by a section on the various
-REFERENCE(Streaming protocols, streaming protocols) in which the data
-connections are described. The way audio file headers are embedded into
-the stream is discussed REFERENCE(Streams with headers and headerless
-streams, briefly) before the REFERENCE(Networking examples, example
-section) which illustrates typical commands for real-life scenarios.
-
-Both IPv4 and IPv6 are supported.
-
-The paraslash control service
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-para_server is controlled at runtime via the paraslash control
-connection. This connection is used for server commands (play, stop,
-...) as well as for afs commands (ls, select, ...).
-
-The server listens on a TCP port and accepts connections from clients
-that connect the open port. Each connection causes the server to fork
-off a client process which inherits the connection and deals with that
-client only. In this classical accept/fork approach the server process
-is unaffected if the child dies or goes crazy for whatever reason. In
-fact, the child process can not change address space of server process.
-
-The section on REFERENCE(Client-server authentication, client-server
-authentication) above described the early connection establishment
-from the crypto point of view. Here it is described what happens
-after the connection (including crypto setup) has been established.
-There are four processes involved during command dispatch as sketched
-in the following diagram.
-
-<<
-<pre>
- server_host client_host
- ~~~~~~~~~~~ ~~~~~~~~~~~
-
- +-----------+ connect +-----------+
- |para_server|<------------------------------ |para_client|
- +-----------+ +-----------+
- | ^
- | fork +---+ |
- +----------> |AFS| |
- | +---+ |
- | ^ |
- | | |
- | | connect (cookie) |
- | | |
- | | |
- | fork +-----+ inherited connection |
- +---------->|child|<--------------------------+
- +-----+
-</pre>
->>
-
-Note that the child process is not a child of the afs process,
-so communication of these two processes has to happen via local
-sockets. In order to avoid abuse of the local socket by unrelated
-processes, a magic cookie is created once at server startup time just
-before the server process forks off the AFS process. This cookie is
-known to the server, AFS and the child, but not to unrelated processes.
-
-There are two different kinds of commands: First there are commands
-that cause the server to respond with some answer such as the list
-of all audio files. All but the addblob commands (addimg, addlyr,
-addpl, addmood) are of this kind. The addblob commands add contents
-to the database, so they need to transfer data the other way round,
-from the client to the server.
-
-There is no knowledge about the server commands built into para_client,
-so it does not know about addblob commands. Instead, the server sends
-a special "awaiting data" packet for these commands. If the client
-receives this packet, it sends STDIN to the server, otherwise it
-dumps data from the server to STDOUT.
-
-Streaming protocols
-~~~~~~~~~~~~~~~~~~~
-
-A network (audio) stream usually consists of one streaming source,
-the _sender_, and one or more _receivers_ which read data over the
-network from the streaming source.
-
-Senders are thus part of para_server while receivers are part of
-para_audiod. Moreover, there is the stand-alone tool para_recv which
-can be used to manually download a stream, either from para_server
-or from a web-based audio streaming service.
-
-The following three streaming protocols are supported by paraslash:
-
- - HTTP. Recommended for public streams that can be played by
- any player like mpg123, xmms, itunes, winamp, etc. The HTTP
- sender is supported on all operating systems and all platforms.
-
- - DCCP. Recommended for LAN streaming. DCCP is currently
- available only for Linux.
-
- - UDP. Recommended for multicast LAN streaming.
-
-See the Appendix on REFERENCE(Network protocols, network protocols)
-for brief descriptions of the various protocols relevant for network
-audio streaming with paraslash.
-
-It is possible to activate more than one sender simultaneously.
-Senders can be controlled at run time and via config file and command
-line options.
-
-Note that audio connections are _not_ encrypted. Transport or Internet
-layer encryption should be used if encrypted data connections are
-needed.
-
-Since DCCP and TCP are both connection-oriented protocols, connection
-establishment/teardown and access control are very similar between
-these two streaming protocols. UDP is the most lightweight option,
-since in contrast to TCP/DCCP it is connectionless. It is also the
-only protocol supporting IP multicast.
-
-The HTTP and the DCCP sender listen on a (TCP/DCCP) port waiting for
-clients to connect and establish a connection via some protocol-defined
-handshake mechanism. Both senders maintain two linked lists each:
-The list of all clients which are currently connected, and the list
-of access control entries which determines who is allowed to connect.
-IP-based access control may be configured through config file and
-command line options and via the "allow" and "deny" sender subcommands.
-
-Upon receiving a GET request from the client, the HTTP sender sends
-back a status line and a message. The body of this message is the
-audio stream. This is common practice and is supported by many popular
-clients which can thus be used to play a stream offered by para_server.
-For DCCP things are a bit simpler: No messages are exchanged between
-the receiver and sender. The client simply connects and the sender
-starts to stream.
-
-DCCP is an experimental protocol which offers a number of new features
-not available for TCP. Both ends can negotiate these features using
-a built-in negotiation mechanism. In contrast to TCP/HTTP, DCCP is
-datagram-based (no retransmissions) and thus should not be used over
-lossy media (e.g. WiFi networks). One useful feature offered by DCCP
-is access to a variety of different congestion-control mechanisms
-called CCIDs. Two different CCIDs are available per default on Linux:
-
-
- - _CCID 2_. A Congestion Control mechanism similar to that
- of TCP. The sender maintains a congestion window and halves
- this window in response to congestion.
-
-
- - _CCID-3_. Designed to be fair when competing for bandwidth.
- It has lower variation of throughput over time compared with
- TCP, which makes it suitable for streaming media.
-
-Unlike the HTTP and DCCP senders, the UDP sender maintains only a
-single list, the _target list_. This list describes the set of clients
-to which the stream is sent. There is no list for access control and
-no "allow" and "deny" commands for the UDP sender. Instead, the "add"
-and "delete" commands can be used to modify the target list.
-
-Since both UDP and DCCP offer an unreliable datagram-based transport,
-additional measures are necessary to guard against disruptions over
-networks that are lossy or which may be subject to interference (as
-is for instance the case with WiFi). Paraslash uses FEC (Forward
-Error Correction) to guard against packet losses and reordering. The
-stream is FEC-encoded before it is sent through the UDP socket and
-must be decoded accordingly on the receiver side.
-
-The packet size and the amount of redundancy introduced by FEC can
-be configured via the FEC parameters which are dictated by server
-and may also be configured through the "sender" command. The FEC
-parameters are encoded in the header of each network packet, so no
-configuration is necessary on the receiver side. See the section on
-REFERENCE(Forward error correction, FEC) below.
-
-Streams with headers and headerless streams
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-For OGG/Vorbis, OGG/Speex and wma streams, some of the information
-needed to decode the stream is only contained in the audio file
-header of the container format but not in each data chunk. Clients
-must be able to obtain this information in case streaming starts in
-the middle of the file or if para_audiod is started while para_server
-is already sending a stream.
-
-This is accomplished in different ways, depending on the streaming
-protocol. For connection-oriented streams (HTTP, DCCP) the audio file
-header is sent prior to audio file data. This technique however does
-not work for the connectionless UDP transport. Hence the audio file
-header is periodically being embedded into the UDP audio data stream.
-By default, the header is resent after five seconds. The receiver has
-to wait until the next header arrives before it can start decoding
-the stream.
-
-Examples
-~~~~~~~~
-
-The "si" (server info) command lists some information about the
-currently running server process.
-
--> Show PIDs, number of connected clients, uptime, and more:
-
- para_client si
-
-The sender command of para_server prints information about senders,
-like the various access control lists, and it allows to (de-)activate
-senders and to change the access permissions at runtime.
-
--> List all senders
-
- para_client sender
-
--> Obtain general help for the sender command:
-
- para_client help sender
-
--> Get help for a specific sender (contains further examples):
-
- s=http # or dccp or udp
- para_client sender $s help
-
--> Show status of the http sender
-
- para_client sender http status
-
-By default para_server activates both the HTTP and th DCCP sender on
-startup. This can be changed via command line options or para_server's
-config file.
-
--> List config file options for senders:
-
- para_server -h
-
-All senders share the "on" and "off" commands, so senders may be
-activated and deactivated independently of each other.
-
--> Switch off the http sender:
-
- para_client sender http off
-
--> Receive a DCCP stream using CCID2 and write the output into a file:
-
- host=foo.org; ccid=2; filename=bar
- para_recv --receiver "dccp --host $host --ccid $ccid" > $filename
-
-Note the quotes around the arguments for the dccp receiver. Each
-receiver has its own set of command line options and its own command
-line parser, so arguments for the dccp receiver must be protected
-from being interpreted by para_recv.
-
--> Start UDP multicast, using the default multicast address:
-
- para_client sender udp add 224.0.1.38
-
--> Receive FEC-encoded multicast stream and write the output into a file:
-
- filename=foo
- para_recv -r udp > $filename
-
--> Add an UDP unicast for a client to the target list of the UDP sender:
-
- t=client.foo.org
- para_client sender udp add $t
-
--> Receive this (FEC-encoded) unicast stream:
-
- filename=foo
- para_recv -r 'udp -i 0.0.0.0' > $filename
-
--> Create a minimal config for para_audiod for HTTP streams:
-
- c=$HOME/.paraslash/audiod.conf.min; s=server.foo.com
- echo receiver \".:http -i $s\" > $c
- para_audiod --config $c
-
--------
-Filters
--------
-
-A paraslash filter is a module which transforms an input stream into
-an output stream. Filters are included in the para_audiod executable
-and in the stand-alone tool para_filter which usually contains the
-same modules.
-
-While para_filter reads its input stream from STDIN and writes
-the output to STDOUT, the filter modules of para_audiod are always
-connected to a receiver which produces the input stream and a writer
-which absorbs the output stream.
-
-Some filters depend on a specific library and are not compiled in
-if this library was not found at compile time. To see the list of
-supported filters, run para_filter and para_audiod with the --help
-option. The output looks similar to the following:
-
- Available filters:
- compress wav amp fecdec wmadec prebuffer oggdec aacdec mp3dec
-
-Out of these filter modules, a chain of filters can be constructed,
-much in the way Unix pipes can be chained, and analogous to the use
-of modules in gstreamer: The output of the first filter becomes the
-input of the second filter. There is no limitation on the number of
-filters and the same filter may occur more than once.
-
-Like receivers, each filter has its own command line options which
-must be quoted to protect them from the command line options of
-the driving application (para_audiod or para_filter). Example:
-
- para_filter -f 'mp3dec --ignore-crc' -f 'compress --damp 1'
-
-For para_audiod, each audio format has its own set of filters. The
-name of the audio format for which the filter should be applied can
-be used as the prefix for the filter option. Example:
-
- para_audiod -f 'mp3:prebuffer --duration 300'
-
-The "mp3" prefix above is actually interpreted as a POSIX extended
-regular expression. Therefore
-
- para_audiod -f '.:prebuffer --duration 300'
-
-activates the prebuffer filter for all supported audio formats (because
-"." matches all audio formats) while
-
- para_audiod -f 'wma|ogg:prebuffer --duration 300'
-
-activates it only for wma and ogg streams.
-
-Decoders
-~~~~~~~~
-
-For each supported audio format there is a corresponding filter
-which decodes audio data in this format to 16 bit PCM data which
-can be directly sent to the sound device or any other software that
-operates on undecoded PCM data (visualizers, equalizers etc.). Such
-filters are called _decoders_ in general, and xxxdec is the name of
-the paraslash decoder for the audio format xxx. For example, the mp3
-decoder is called mp3dec.
-
-Note that the output of the decoder is about 10 times larger than
-its input. This means that filters that operate on the decoded audio
-stream have to deal with much more data than filters that transform
-the audio stream before it is fed to the decoder.
-
-Paraslash relies on external libraries for most decoders, so these
-libraries must be installed for the decoder to be included in the
-executables. For example, the mp3dec filter depends on the mad library.
-
-Forward error correction
-~~~~~~~~~~~~~~~~~~~~~~~~
-
-As already mentioned REFERENCE(Streaming protocols, earlier),
-paraslash uses forward error correction (FEC) for the unreliable UDP
-and DCCP transports. FEC is a technique which was invented already
-in 1960 by Reed and Solomon and which is widely used for the parity
-calculations of storage devices (RAID arrays). It is based on the
-algebraic concept of finite fields, today called Galois fields, in
-honour of the mathematician Galois (1811-1832). The FEC implementation
-of paraslash is based on code by Luigi Rizzo.
-
-Although the details require a sound knowledge of the underlying
-mathematics, the basic idea is not hard to understand: For positive
-integers k and n with k < n it is possible to compute for any k given
-data bytes d_1, ..., d_k the corresponding r := n -k parity bytes p_1,
-..., p_r such that all data bytes can be reconstructed from *any*
-k bytes of the set
-
- {d_1, ..., d_k, p_1, ..., p_r}.
-
-FEC-encoding for unreliable network transports boils down to slicing
-the audio stream into groups of k suitably sized pieces called _slices_
-and computing the r corresponding parity slices. This step is performed
-in para_server which then sends both the data and the parity slices
-over the unreliable network connection. If the client was able
-to receive at least k of the n = k + r slices, it can reconstruct
-(FEC-decode) the original audio stream.
-
-From these observations it is clear that there are three different
-FEC parameters: The slice size, the number of data slices k, and the
-total number of slices n. It is crucial to choose the slice size
-such that no fragmentation of network packets takes place because
-FEC only guards against losses and reordering but fails if slices are
-received partially.
-
-FEC decoding in paralash is performed through the fecdec filter which
-usually is the first filter (there can be other filters before fecdec
-if these do not alter the audio stream).
-
-
-Volume adjustment (amp and compress)
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The amp and the compress filter both adjust the volume of the audio
-stream. These filters operate on uncompressed audio samples. Hence
-they are usually placed directly after the decoding filter. Each
-sample is multiplied with a scaling factor (>= 1) which makes amp
-and compress quite expensive in terms of computing power.
-
-*amp*
-
-The amp filter amplifies the audio stream by a fixed scaling factor
-that must be known in advance. For para_audiod this factor is derived
-from the amplification field of the audio file's entry in the audio
-file table while para_filter uses the value given at the command line.
-
-The optimal scaling factor F for an audio file is the largest real
-number F >= 1 such that after multiplication with F all samples still
-fit into the sample interval [-32768, 32767]. One can use para_filter
-in combination with the sox utility to compute F:
-
- para_filter -f mp3dec -f wav < file.mp3 | sox -t wav - -e stat -v
-
-The amplification value V which is stored in the audio file table,
-however, is an integer between 0 and 255 which is connected to F
-through the formula
-
- V = (F - 1) * 64.
-
-To store V in the audio file table, the command
-
- para_client -- touch -a=V file.mp3
-
-is used. The reader is encouraged to write a script that performs
-these computations :)
-
-*compress*
-
-Unlike the amplification filter, the compress filter adjusts the volume
-of the audio stream dynamically without prior knowledge about the peak
-value. It maintains the maximal volume of the last n samples of the
-audio stream and computes a suitable amplification factor based on that
-value and the various configuration options. It tries to chose this
-factor such that the adjusted volume meets the desired target level.
-
-Note that it makes sense to combine amp and compress.
-
-Misc filters (wav and prebuffer)
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-These filters are rather simple and do not modify the audio stream at
-all. The wav filter is only useful with para_filter and in connection
-with a decoder. It asks the decoder for the number of channels and the
-sample rate of the stream and adds a Microsoft wave header containing
-this information at the beginning. This allows to write wav files
-rather than raw PCM files (which do not contain any information about
-the number of channels and the sample rate).
-
-The prebuffer filter simply delays the output until the given time has
-passed (starting from the time the first byte was available in its
-input queue) or until the given amount of data has accumulated. It
-is mainly useful for para_audiod if the standard parameters result
-in buffer underruns.
-
-Both filters require almost no additional computing time, even when
-operating on uncompressed audio streams, since data buffers are simply
-"pushed down" rather than copied.
-
-Examples
-~~~~~~~~
-
--> Decode an mp3 file to wav format:
-
- para_filter -f mp3dec -f wav < file.mp3 > file.wav
-
--> Amplify a raw audio file by a factor of 1.5:
-
- para_filter -f amp --amp 32 < foo.raw > bar.raw
-
-------
-Output
-------
-
-Once an audio stream has been received and decoded to PCM format,
-it can be sent to a sound device for playback. This part is performed
-by paraslash _writers_ which are described in this chapter.
-
-Writers
-~~~~~~~
-
-A paraslash writer acts as a data sink that consumes but does not
-produce audio data. Paraslash writers operate on the client side and
-are contained in para_audiod and in the stand-alone tool para_write.
-
-The para_write program reads uncompressed audio data from STDIN. If
-this data starts with a wav header, sample rate, sample format and
-channel count are read from the header. Otherwise CD audio (44.1KHz
-16 bit little endian, stereo) is assumed but this can be overridden
-by command line options. para_audiod, on the other hand, obtains
-the sample rate and the number of channels from the decoder.
-
-Like receivers and filters, each writer has an individual set of
-command line options, and for para_audiod writers can be configured
-per audio format separately. It is possible to activate more than
-one writer for the same stream simultaneously.
-
-OS-dependent APIs
-~~~~~~~~~~~~~~~~~
-
-Unfortunately, the various flavours of Unix on which paraslash
-runs on have different APIs for opening a sound device and starting
-playback. Hence for each such API there is a paraslash writer that
-can play the audio stream via this API.
-
-*ALSA*. The _Advanced Linux Sound Architecture_ is only available on
-Linux systems. Although there are several mid-layer APIs in use by
-the various Linux distributions (ESD, Jack, PulseAudio), paraslash
-currently supports only the low-level ALSA API which is not supposed
-to be change. ALSA is very feature-rich, in particular it supports
-software mixing via its DMIX plugin. ALSA is the default writer on
-Linux systems.
-
-*OSS*. The _Open Sound System_ is the only API on *BSD Unixes and
-is also available on Linux systems, usually provided by ALSA as an
-emulation for backwards compatibility. This API is rather simple but
-also limited. For example only one application can open the device
-at any time. The OSS writer is activated by default on BSD Systems.
-
-*OSX*. Mac OS X has yet another API called CoreAudio. The OSX writer
-for this API is only compiled in on such systems and is of course
-the default there.
-
-*FILE*. The file writer allows to capture the audio stream and
-write the PCM data to a file on the file system rather than playing
-it through a sound device. It is supported on all platforms and is
-always compiled in.
-
-*AO*. _Libao_ is a cross-platform audio library which supports a wide
-variety of platforms including PulseAudio (gnome), ESD (Enlightened
-Sound Daemon), AIX, Solaris and IRIX. The ao writer plays audio
-through an output plugin of libao.
-
-Examples
-~~~~~~~~
-
--> Use the OSS writer to play a wav file:
-
- para_write --writer oss < file.wav
-
--> Enable ALSA software mixing for mp3 streams
-
- para_audiod --writer 'mp3:alsa -d plug:swmix'
-
-
----
-Gui
----
-
-para_gui executes an arbitrary command which is supposed to print
-status information to STDOUT. It then displays this information in
-a curses window. By default the command
-
- para_audioc -- stat -p
-
-is executed, but this can be customized via the --stat-cmd option. In
-particular it possible to use
-
- para_client -- stat -p
-
-to make para_gui work on systems on which para_audiod is not running.
-
-Key bindings
-~~~~~~~~~~~~
-
-It is possible to bind keys to arbitrary commands via custom
-key-bindings. Besides the internal keys which can not be changed (help,
-quit, loglevel, version...), the following flavours of key-bindings
-are supported:
-
- - external: Shutdown curses before launching the given command.
- Useful for starting other ncurses programs from within
- para_gui, e.g. aumix or dialog scripts. Or, use the mbox
- output format to write a mailbox containing one mail for each
- (admissible) file the audio file selector knows about. Then
- start mutt from within para_gui to browse your collection!
-
- - display: Launch the command and display its stdout in
- para_gui's bottom window.
-
- - para: Like display, but start "para_client <specified
- command>" instead of "<specified command>".
-
-The general form of a key binding is
-
- key_map k:m:c
-
-which maps key k to command c using mode m. Mode may be x, d or p
-for external, display and paraslash commands, respectively.
-
-Themes
-~~~~~~
-
-Currently there are only two themes for para_gui. It is easy, however,
-to add more themes. To create a new theme one has to define the
-position, color and geometry for for each status item that should be
-shown by this theme. See gui_theme.c for examples.
-
-The "." and "," keys are used to switch between themes.
-
-Examples
-~~~~~~~~
-
--> Show server info:
-
- key_map "i:p:si"
-
--> Jump to the middle of the current audio file by pressing F5:
-
- key_map "<F5>:p:jmp 50"
-
--> vi-like bindings for jumping around:
-
- key_map "l:p:ff 10"
- key_map "h:p:ff 10-"
- key_map "w:p:ff 60"
- key_map "b:p:ff 60-"
-
--> Print the current date and time:
-
- key_map "D:d:date"
-
--> Call other curses programs:
-
- key_map "U:x:aumix"
- key_map "!:x:/bin/bash"
- key_map "^E:x:/bin/sh -c 'vi ~/.paraslash/gui.conf'"
-
------------
-Development
------------
-
-Tools
-~~~~~
-
-In order to compile the sources from the git repository (rather than
-from tar balls) and for contributing non-trivial changes to the
-paraslash project, some additional tools should be installed on a
-developer machine.
-
-http://git.or.cz/ (git). As described in more detail REFERENCE(Git
-branches, below), the git source code management tool is used for
-paraslash development. It is necessary for cloning the git repository
-and for getting updates.
-
-ftp://ftp.gnu.org/pub/gnu/m4/ (m4). Some input files for gengetopt
-are generated from templates by the m4 macro processor.
-
-ftp://ftp.gnu.org/pub/gnu/autoconf/ (autoconf) GNU autoconf creates
-the configure file which is shipped in the tarballs but has to be
-generated when compiling from git.
-
-http://www.triptico.com/software/grutatxt.html (grutatxt). The
-HTML version of this manual and some of the paraslash web pages are
-generated by the grutatxt plain text to HTML converter. If changes
-are made to these text files the grutatxt package must be installed
-to regenerate the HTML files.
-
-http://www.stack.nl/~dimitri/doxygen/ (doxygen). The documentation
-of paraslash's C sources uses the doxygen documentation system. The
-conventions for documenting the source code is described in the
-REFERENCE(Doxygen, Doxygen section).
-
-ftp://ftp.gnu.org/pub/gnu/global (global). This is used to generate
-browsable HTML from the C sources. It is needed by doxygen.
-
-Git branches
-~~~~~~~~~~~~
-
-Paraslash has been developed using the git source code management
-tool since 2006. Development is organized roughly in the same spirit
-as the git development itself, as described below.
-
-The following text passage is based on "A note from the maintainer",
-written by Junio C Hamano, the maintainer of git.
-
-There are four branches in the paraslash repository that track the
-source tree: "master", "maint", "next", and "pu".
-
-The "master" branch is meant to contain what is well tested and
-ready to be used in a production setting. There could occasionally be
-minor breakages or brown paper bag bugs but they are not expected to
-be anything major, and more importantly quickly and easily fixable.
-Every now and then, a "feature release" is cut from the tip of this
-branch, named with three dotted decimal digits, like 0.4.2.
-
-Whenever changes are about to be included that will eventually lead to
-a new major release (e.g. 0.5.0), a "maint" branch is forked off from
-"master" at that point. Obvious, safe and urgent fixes after the major
-release are applied to this branch and maintenance releases are cut
-from it. New features never go to this branch. This branch is also
-merged into "master" to propagate the fixes forward.
-
-A trivial and safe enhancement goes directly on top of "master".
-New development does not usually happen on "master", however.
-Instead, a separate topic branch is forked from the tip of "master",
-and it first is tested in isolation; Usually there are a handful such
-topic branches that are running ahead of "master". The tip of these
-branches is not published in the public repository to keep the number
-of branches that downstream developers need to worry about low.
-
-The quality of topic branches varies widely. Some of them start out as
-"good idea but obviously is broken in some areas" and then with some
-more work become "more or less done and can now be tested by wider
-audience". Luckily, most of them start out in the latter, better shape.
-
-The "next" branch is to merge and test topic branches in the latter
-category. In general, this branch always contains the tip of "master".
-It might not be quite rock-solid production ready, but is expected to
-work more or less without major breakage. The maintainer usually uses
-the "next" version of paraslash for his own pleasure, so it cannot
-be _that_ broken. The "next" branch is where new and exciting things
-take place.
-
-The two branches "master" and "maint" are never rewound, and "next"
-usually will not be either (this automatically means the topics that
-have been merged into "next" are usually not rebased, and you can find
-the tip of topic branches you are interested in from the output of
-"git log next"). You should be able to safely build on top of them.
-
-However, at times "next" will be rebuilt from the tip of "master" to
-get rid of merge commits that will never be in "master". The commit
-that replaces "next" will usually have the identical tree, but it
-will have different ancestry from the tip of "master".
-
-The "pu" (proposed updates) branch bundles the remainder of the
-topic branches. The "pu" branch, and topic branches that are only in
-"pu", are subject to rebasing in general. By the above definition
-of how "next" works, you can tell that this branch will contain quite
-experimental and obviously broken stuff.
-
-When a topic that was in "pu" proves to be in testable shape, it
-graduates to "next". This is done with
-
- git checkout next
- git merge that-topic-branch
-
-Sometimes, an idea that looked promising turns out to be not so good
-and the topic can be dropped from "pu" in such a case.
-
-A topic that is in "next" is expected to be polished to perfection
-before it is merged to "master". Similar to the above, this is
-done with
-
- git checkout master
- git merge that-topic-branch
- git branch -d that-topic-branch
-
-Note that being in "next" is not a guarantee to appear in the next
-release (being in "master" is such a guarantee, unless it is later
-found seriously broken and reverted), nor even in any future release.
-
-Coding Style
-~~~~~~~~~~~~
-
-The preferred coding style for paraslash coincides more or less
-with the style of the Linux kernel. So rather than repeating what is
-written XREFERENCE(http://www.kernel.org/doc/Documentation/CodingStyle,
-there), here are the most important points.
-
- - Burn the GNU coding standards.
- - Never use spaces for indentation.
- - Tabs are 8 characters, and thus indentations are also 8 characters.
- - Don't put multiple assignments on a single line.
- - Avoid tricky expressions.
- - Don't leave whitespace at the end of lines.
- - The limit on the length of lines is 80 columns.
- - Use K&R style for placing braces and spaces:
-
- if (x is true) {
- we do y
- }
-
- - Use a space after (most) keywords.
- - Do not add spaces around (inside) parenthesized expressions.
- - Use one space around (on each side of) most binary and ternary operators.
- - Do not use cute names like ThisVariableIsATemporaryCounter, call it tmp.
- - Mixed-case names are frowned upon.
- - Descriptive names for global variables are a must.
- - Avoid typedefs.
- - Functions should be short and sweet, and do just one thing.
- - The number of local variables shouldn't exceed 10.
- - Gotos are fine if they improve readability and reduce nesting.
- - Don't use C99-style "// ..." comments.
- - Names of macros defining constants and labels in enums are capitalized.
- - Enums are preferred when defining several related constants.
- - Always use the paraslash wrappers for allocating memory.
- - If the name of a function is an action or an imperative.
- command, the function should return an error-code integer
- (<0 means error, >=0 means success). If the name is a
- predicate, the function should return a "succeeded" boolean.
-
-
-Doxygen
-~~~~~~~
-
-Doxygen is a documentation system for various programming
-languages. The API reference on the paraslash web page is generated
-by doxygen.
-
-It is more illustrative to look at the source code for examples than
-to describe the conventions in this manual, so we only describe which
-parts of the code need doxygen comments, but leave out details on
-documentation conventions.
-
-As a rule, only the public part of the C source is documented with
-Doxygen. This includes structures, defines and enumerations in header
-files as well as public (non-static) C functions. These should be
-documented completely. For example, each parameter and the return
-value of a public function should get a descriptive doxygen comment.
-
-No doxygen comments are necessary for static functions and for
-structures and enumerations in C files (which are used only within
-this file). This does not mean, however, that those entities need
-no documentation at all. Instead, common sense should be applied to
-document what is not obvious from reading the code.
-
---------
-Appendix
---------
-
-Network protocols
-~~~~~~~~~~~~~~~~~
-
-*IP*. The _Internet Protocol_ is the primary networking protocol
-used for the Internet. All protocols described below use IP as the
-underlying layer. Both the prevalent IPv4 and the next-generation
-IPv6 variant are being deployed actively worldwide.
-
-*Connection-oriented and connectionless protocols*. Connectionless
-protocols differ from connection-oriented ones in that state
-associated with the sending/receiving endpoints is treated
-implicitly. Connectionless protocols maintain no internal knowledge
-about the state of the connection. Hence they are not capable of
-reacting to state changes, such as sudden loss or congestion on the
-connection medium. Connection-oriented protocols, in contrast, make
-this knowledge explicit. The connection is established only after
-a bidirectional handshake which requires both endpoints to agree
-on the state of the connection, and may also involve negotiating
-specific parameters for the particular connection. Maintaining an
-up-to-date internal state of the connection also in general means
-that the sending endpoints perform congestion control, adapting to
-qualitative changes of the connection medium.
-
-*Reliability*. In IP networking, packets can be lost, duplicated,
-or delivered out of order, and different network protocols handle
-these problems in different ways. We call a transport-layer protocol
-_reliable_, if it turns the unreliable IP delivery into an ordered,
-duplicate- and loss-free delivery of packets. Sequence numbers
-are used to discard duplicates and re-arrange packets delivered
-out-of-order. Retransmission is used to guarantee loss-free
-delivery. Unreliable protocols, in contrast, do not guarantee ordering
-or data integrity.
-
-*Classification*. With these definitions the protocols which are used
-by paraslash for steaming audio data may be classified as follows.
-
- - HTTP/TCP: connection-oriented, reliable,
- - UDP: connectionless, unreliable,
- - DCCP: connection-oriented, unreliable.
-
-Below we give a short descriptions of these protocols.
-
-*TCP*. The _Transmission Control Protocol_ provides reliable,
-ordered delivery of a stream and a classic window-based congestion
-control. In contrast to UDP and DCCP (see below), TCP does not have
-record-oriented or datagram-based syntax, i.e. it provides a stream
-which is unaware and independent of any record (packet) boundaries.
-TCP is used extensively by many application layers. Besides HTTP (the
-Hypertext Transfer Protocol), also FTP (the File Transfer protocol),
-SMTP (Simple Mail Transfer Protocol), SSH (Secure Shell) all sit on
-top of TCP.
-
-*UDP*. The _User Datagram Protocol_ is the simplest transport-layer
-protocol, built as a thin layer directly on top of IP. For this reason,
-it offers the same best-effort service as IP itself, i.e. there is no
-detection of duplicate or reordered packets. Being a connectionless
-protocol, only minimal internal state about the connection is
-maintained, which means that there is no protection against packet
-loss or network congestion. Error checking and correction (if at all)
-are performed in the application.
-
-*DCCP*. The _Datagram Congestion Control Protocol_ combines the
-connection-oriented state maintenance known from TCP with the
-unreliable, datagram-based transport of UDP. This means that it
-is capable of reacting to changes in the connection by performing
-congestion control, offering multiple alternative approaches. But it
-is bound to datagram boundaries (the maximum packet size supported
-by a medium), and like UDP it lacks retransmission to protect
-against loss. Due to the use of sequence numbers, it is however
-able to react to loss (interpreted as a congestion indication) and
-to ignore out-of-order and duplicate packets. Unlike TCP it allows
-to negotiate specific, binding features for a connection, such as
-the choice of congestion control: classic, window-based congestion
-control known from TCP is available as CCID-2, rate-based, "smooth"
-congestion control is offered as CCID-3.
-
-*HTTP*. _The Hypertext Transfer Protocol_ is an application layer
-protocol on top of TCP. It is spoken by web servers and is most often
-used for web services. However, as can be seen by the many Internet
-radio stations and YouTube/Flash videos, http is by far not limited to
-the delivery of web pages only. Being a simple request/response based
-protocol, the semantics of the protocol also allow the delivery of
-multimedia content, such as audio over http.
-
-*Multicast*. IP multicast is not really a protocol but a technique
-for one-to-many communication over an IP network. The challenge is to
-deliver information to a group of destinations simultaneously using
-the most efficient strategy to send the messages over each link of
-the network only once. This has benefits for streaming multimedia:
-the standard one-to-one unicast offered by TCP/DCCP means that
-n clients listening to the same stream also consume n-times the
-resources, whereas multicast requires to send the stream just once,
-irrespective of the number of receivers. Since it would be costly to
-maintain state for each listening receiver, multicast often implies
-connectionless transport, which is the reason that it is currently
-only available via UDP.
-
-Abstract socket namespace
-~~~~~~~~~~~~~~~~~~~~~~~~~
-UNIX domain sockets are a traditional way to communicate between
-processes on the same machine. They are always reliable (see above)
-and don't reorder datagrams. Unlike TCP and UDP, UNIX domain sockets
-support passing open file descriptors or process credentials to
-other processes.
-
-The usual way to set up a UNIX domain socket (as obtained from
-socket(2)) for listening is to first bind the socket to a file system
-pathname and then call listen(2), then accept(2). Such sockets are
-called _pathname sockets_ because bind(2) creates a special socket
-file at the specified path. Pathname sockets allow unrelated processes
-to communicate with the listening process by binding to the same path
-and calling connect(2).
-
-There are two problems with pathname sockets:
-
- * The listing process must be able to (safely) create the
- socket special in a directory which is also accessible to
- the connecting process.
-
- * After an unclean shutdown of the listening process, a stale
- socket special may reside on the file system.
-
-The abstract socket namespace is a non-portable Linux feature which
-avoids these problems. Abstract sockets are still bound to a name,
-but the name has no connection with file system pathnames.
-
-License
-~~~~~~~
-
-Paraslash is licensed under the GPL, version 2. Most of the code
-base has been written from scratch, and those parts are GPL V2
-throughout. Notable exceptions are FEC and the WMA decoder. See the
-corresponding source files for licencing details for these parts. Some
-code sniplets of several other third party software packages have
-been incorporated into the paraslash sources, for example log message
-coloring was taken from the git sources. These third party software
-packages are all published under the GPL or some other license
-compatible to the GPL.
-
-Acknowledgements
-~~~~~~~~~~~~~~~~
-
-Many thanks to Gerrit Renker who read an early draft of this manual
-and contributed significant improvements.
-
-----------
-References
-----------
-
-Articles
-~~~~~~~~
- - Reed, Irving S.; Solomon, Gustave (1960),
- XREFERENCE(http://kom.aau.dk/~heb/kurser/NOTER/KOFA01.PDF,
- Polynomial Codes over Certain Finite Fields), Journal of the
- Society for Industrial and Applied Mathematics (SIAM) 8 (2):
- 300-304, doi:10.1137/0108018)
-
-RFCs
-~~~~
-
- - XREFERENCE(http://www.ietf.org/rfc/rfc768.txt, RFC 768) (1980):
- User Datagram Protocol
- - XREFERENCE(http://www.ietf.org/rfc/rfc791.txt, RFC 791) (1981):
- Internet Protocol
- - XREFERENCE(http://www.ietf.org/rfc/rfc2437.txt, RFC 2437) (1998):
- RSA Cryptography Specifications
- - XREFERENCE(http://www.ietf.org/rfc/rfc4340.txt, RFC 4340)
- (2006): Datagram Congestion Control Protocol (DCCP)
- - XREFERENCE(http://www.ietf.org/rfc/rfc4341.txt, RFC 4341) (2006):
- Congestion Control ID 2: TCP-like Congestion Control
- - XREFERENCE(http://www.ietf.org/rfc/rfc4342.txt, RFC 4342) (2006):
- Congestion Control ID 3: TCP-Friendly Rate Control (TFRC)
- - XREFERENCE(http://www.ietf.org/rfc/rfc6716.txt, RFC 6716) (2012):
- Definition of the Opus Audio Codec
-
-Application web pages
-~~~~~~~~~~~~~~~~~~~~~
-
- - XREFERENCE(http://people.tuebingen.mpg.de/maan/paraslash/, paraslash)
- - XREFERENCE(http://paraslash.systemlinux.org/, paraslash (alternative page))
- - XREFERENCE(http://xmms2.org/wiki/Main_Page, xmms)
- - XREFERENCE(http://www.mpg123.de/, mpg123)
- - XREFERENCE(http://gstreamer.freedesktop.org/, gstreamer)
- - XREFERENCE(http://www.icecast.org/, icecast)
- - XREFERENCE(http://beesbuzz.biz/code/audiocompress.php, Audio Compress)
-
-External documentation
-~~~~~~~~~~~~~~~~~~~~~~
-
- - XREFERENCE(http://kernel.org/pub/linux/kernel/people/hpa/raid6.pdf,
- H. Peter Anvin: The mathematics of Raid6)
- - XREFERENCE(http://info.iet.unipi.it/~luigi/fec_ccr.ps.gz,
- Luigi Rizzo: Effective Erasure Codes for reliable Computer
- Communication Protocols)
-
-Code
-~~~~
- - XREFERENCE(http://info.iet.unipi.it/~luigi/vdm.tar.gz,
- Original FEC implementation by Luigi Rizzo)
-
--- /dev/null
+**Paraslash user manual**
+
+This document describes how to install, configure and use the paraslash
+network audio streaming system. Most chapters start with a chapter
+overview and conclude with an example section. We try to focus on
+general concepts and on the interaction of the various pieces of the
+paraslash package. Hence this user manual is not meant as a replacement
+for the manual pages that describe all command line options of each
+paraslash executable.
+
+============
+Introduction
+============
+
+In this chapter we give an [overview](#Overview) of the interactions of
+the two main programs contained in the paraslash package, followed by
+[brief descriptions](#The.paraslash.executables) of all executables.
+
+Overview
+--------
+
+The core functionality of the para suite is provided by two main
+executables, para_server and para_audiod. The former maintains a
+database of audio files and streams these files to para_audiod which
+receives and plays the stream.
+
+In a typical setting, both para_server and para_audiod act as
+background daemons whose functionality is controlled by client
+programs: the para_audioc client controls para_audiod over a local
+socket while the para_client program connects to para_server over a
+local or remote networking connection.
+
+Typically, these two daemons run on different hosts but a local setup
+is also possible.
+
+A simplified picture of a typical setup is as follows
+
+ server_host client_host
+ ~~~~~~~~~~~ ~~~~~~~~~~~
+
+ +-----------+ audio stream +-----------+
+ |para_server| -----------------------------> |para_audiod|
+ +-----------+ +-----------+
+ ^ ^
+ | |
+ | | connect
+ | |
+ | |
+ | +-----------+
+ | |para_audioc|
+ | +-----------+
+ |
+ |
+ | connect +-----------+
+ +-------------------------------------- |para_client|
+ +-----------+
+The paraslash executables
+-------------------------
+
+### para_server ###
+
+para_server streams binary audio data (MP3, ...) over local and/or
+remote networks. It listens on a TCP port and accepts commands such
+as play, stop, pause, next from authenticated clients. There are
+many more commands though, see the man page of para_server for a
+description of all commands.
+
+It supports three built-in network streaming protocols
+(senders/receivers): HTTP, DCCP, or UDP. This is explained in more
+detail in the section on [networking](#Networking).
+
+The built-in audio file selector of paraslash is used to manage your
+audio files. It maintains statistics on the usage of all available
+audio files such as last-played time, and the number of times each
+file was selected.
+
+Additional information may be added to the database to allow
+fine-grained selection based on various properties of the audio file,
+including information found in (ID3) tags. However, old-fashioned
+playlists are also supported.
+
+It is also possible to store images (album covers) and lyrics in the
+database and associate these to the corresponding audio files.
+
+The section on the [audio file selector](#The.audio.file.selector)
+discusses this topic.
+
+
+### para_client ###
+
+The client program to connect to para_server. paraslash commands
+are sent to para_server and the response is dumped to STDOUT. This
+can be used by any scripting language to produce user interfaces with
+little programming effort.
+
+All connections between para_server and para_client are encrypted
+with a symmetric session key. For each user of paraslash you must
+create a public/secret RSA key pair for authentication.
+
+If para_client is started without non-option arguments, an interactive
+session (shell) is started. Command history and command completion are
+supported through libreadline.
+
+### para_audiod ###
+
+The local daemon that collects information from para_server.
+
+It runs on the client side and connects to para_server. As soon as
+para_server announces the availability of an audio stream, para_audiod
+starts an appropriate receiver, any number of filters and a paraslash
+writer to play the stream.
+
+Moreover, para_audiod listens on a local socket and sends status
+information about para_server and para_audiod to local clients on
+request. Access via this local socket may be restricted by using Unix
+socket credentials, if available.
+
+
+### para_audioc ###
+
+The client program which talks to para_audiod. Used to control
+para_audiod, to receive status info, or to grab the stream at any
+point of the decoding process. Like para_client, para_audioc supports
+interactive sessions on systems with libreadline.
+
+### para_recv ###
+
+A command line HTTP/DCCP/UDP stream grabber. The http mode is
+compatible with arbitrary HTTP streaming sources (e.g. icecast).
+In addition to the three network streaming modes, para_recv can also
+operate in local (afh) mode. In this mode it writes the content of
+an audio file on the local file system in complete chunks to stdout,
+optionally 'just in time'. This allows to cut an audio file without
+first decoding it, and it enables third-party software which is unaware
+of the particular audio format to send complete frames in real time.
+
+### para_filter ###
+
+A filter program that reads from STDIN and writes to STDOUT.
+Like para_recv, this is an atomic building block which can be used to
+assemble higher-level audio receiving facilities. It combines several
+different functionalities in one tool: decoders for multiple audio
+formats and a number of processing filters, among these a normalizer
+for audio volume.
+
+### para_afh ###
+
+A small stand-alone program that prints tech info about the given
+audio file to STDOUT. It can be instructed to print a "chunk table",
+an array of offsets within the audio file.
+
+### para_write ###
+
+A modular audio stream writer. It supports a simple file writer
+output plug-in and optional WAV/raw players for ALSA (Linux) and for
+coreaudio (Mac OS). para_write can also be used as a stand-alone WAV
+or raw audio player.
+
+### para_play ###
+
+A command line audio player.
+
+### para_gui ###
+
+Curses-based gui that presents status information obtained in a curses
+window. Appearance can be customized via themes. para_gui provides
+key-bindings for the most common server commands and new key-bindings
+can be added easily.
+
+### para_fade ###
+
+An alarm clock and volume-fader for OSS and ALSA.
+
+===========
+Quick start
+===========
+
+This chapter lists the [necessary software](#Requirements)
+that must be installed to compile the paraslash package, describes
+how to [compile and install](#Installation) the paraslash
+source code and the steps that have to be performed in order to
+[set up](#Configuration) a typical server and client.
+
+Requirements
+------------
+### For the impatient ###
+
+ git clone git://git.tuebingen.mpg.de/osl
+ cd osl && make && sudo make install && sudo ldconfig
+ sudo apt-get install autoconf libssl-dev help2man gengetopt \
+ libmad0-dev libid3tag0-dev libasound2-dev libvorbis-dev \
+ libfaad-dev libspeex-dev libFLAC-dev libsamplerate-dev \
+ libasound2-dev libao-dev libreadline-dev libncurses-dev \
+ libopus-dev
+
+### Detailed description ###
+
+In any case you will need
+
+- [libosl](http://people.tuebingen.mpg.de/maan/osl/). The _object
+storage layer_ library is used by para_server. To clone the source
+code repository, execute
+
+ git clone git://git.tuebingen.mpg.de/osl
+
+- [gcc](ftp://ftp.gnu.org/pub/gnu/gcc) or
+[clang](http://clang.llvm.org). All gcc versions >= 3.3 are currently
+supported. Clang version 1.1 or newer should work as well.
+
+- [gnu make](ftp://ftp.gnu.org/pub/gnu/make) is also shipped with the
+disto. On BSD systems the gnu make executable is often called gmake.
+
+- [bash](ftp://ftp.gnu.org/pub/gnu/bash). Some scripts which run
+during compilation require the _Bourne again shell_. It is most
+likely already installed.
+
+- [gengetopt](ftp://ftp.gnu.org/pub/gnu/gengetopt/) is needed to
+generate the C code for the command line parsers of all paraslash
+executables.
+
+- [help2man](ftp://ftp.gnu.org/pub/gnu/help2man) is used to create
+the man pages.
+
+Optional:
+
+- [openssl](http://www.openssl.org/) or
+[libgcrypt](ftp://ftp.gnupg.org/gcrypt/libgcrypt/). At least one
+of these two libraries is needed as the backend for cryptographic
+routines on both the server and the client side. Both openssl and
+libgcrypt are usually shipped with the distro, but you might have
+to install the development package (`libssl-dev` or `libgcrypt-dev`
+on debian systems) as well.
+
+- [libmad](http://www.underbit.com/products/mad/). To compile in MP3
+support for paraslash, the development package must be installed. It
+is called `libmad0-dev` on debian-based systems. Note that libmad is
+not necessary on the server side, i.e., for sending MP3 files.
+
+- [libid3tag](http://www.underbit.com/products/mad/). For version-2
+ID3 tag support, you willl need the libid3tag development package
+`libid3tag0-dev`. Without libid3tag, only version-1 tags are
+recognized. The mp3 tagger also needs this library for modifying
+(id3v1 and id3v2) tags.
+
+- [ogg vorbis](http://www.xiph.org/downloads/). For ogg vorbis streams
+you need libogg, libvorbis, libvorbisfile. The corresponding Debian
+packages are called `libogg-dev` and `libvorbis-dev`.
+
+- [libfaad](http://www.audiocoding.com/). For aac files (m4a) you
+need libfaad (`libfaad-dev`).
+
+- [speex](http://www.speex.org/). In order to stream or decode speex
+files, libspeex (`libspeex-dev`) is required.
+
+- [flac](http://flac.sourceforge.net/). To stream or decode files
+encoded with the _Free Lossless Audio Codec_, libFLAC (`libFLAC-dev`)
+must be installed.
+
+- [libsamplerate](http://www.mega-nerd.com/SRC/index.html). The
+resample filter will only be compiled if this library is
+installed. Debian package: `libsamplerate-dev`.
+
+- [alsa-lib](ftp://ftp.alsa-project.org/pub/lib/). On Linux, you will
+need to have the ALSA development package `libasound2-dev` installed.
+
+- [libao](http://downloads.xiph.org/releases/ao/). Needed to build
+the ao writer (ESD, PulseAudio,...). Debian package: `libao-dev`.
+
+- [curses](ftp://ftp.gnu.org/pub/gnu/ncurses). Needed for
+para_gui. Debian package: `libncurses-dev`.
+
+- [GNU
+Readline](http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html). If
+this library (`libreadline-dev`) is installed, para_client, para_audioc
+and para_play support interactive sessions.
+
+Installation
+------------
+To build the sources from a tarball, execute
+
+ ./configure && make
+
+To build from git or a gitweb snapshot, run this command instead:
+
+ ./autogen.sh
+
+There should be no errors but probably some warnings about missing
+packages which usually implies that not all audio formats will be
+supported. If headers or libs are installed at unusual locations you
+might need to tell the configure script where to find them. Try
+
+ ./configure --help
+
+to see a list of options. If the paraslash package was compiled
+successfully, execute (optionally)
+
+ make test
+
+to run the paraslash test suite. If all tests pass, execute as root
+
+ make install
+
+to install executables under /usr/local/bin and the man pages under
+/usr/local/man.
+
+Configuration
+-------------
+
+### Create a paraslash user ###
+
+In order to control para_server at runtime you must create a paraslash
+user. As authentication is based on the RSA crypto system you'll have
+to create an RSA key pair. If you already have a user and an RSA key
+pair, you may skip this step.
+
+In this section we'll assume a typical setup: You would like to run
+para_server on some host called server_host as user foo, and you want
+to connect to para_server from another machine called client_host as
+user bar.
+
+As foo@server_host, create ~/.paraslash/server.users by typing the
+following commands:
+
+ user=bar
+ target=~/.paraslash/server.users
+ key=~/.paraslash/id_rsa.pub.$user
+ perms=AFS_READ,AFS_WRITE,VSS_READ,VSS_WRITE
+ mkdir -p ~/.paraslash
+ echo "user $user $key $perms" >> $target
+
+Next, change to the "bar" account on client_host and generate the
+key pair with the commands
+
+ ssh-keygen -q -t rsa -b 2048 -N '' -f $key
+
+This generates the two files id_rsa and id_rsa.pub in ~/.ssh. Note
+that para_server won't accept keys shorter than 2048 bits. Moreover,
+para_client rejects private keys which are world-readable.
+
+para_server only needs to know the public key of the key pair just
+created. Copy this public key to server_host:
+
+ src=~/.ssh/id_rsa.pub
+ dest=.paraslash/id_rsa.pub.$LOGNAME
+ scp $src foo@server_host:$dest
+
+Finally, tell para_client to connect to server_host:
+
+ conf=~/.paraslash/client.conf
+ echo 'hostname server_host' > $conf
+
+
+### Start para_server ###
+
+For this first try, we'll use the info loglevel to make the output
+of para_server more verbose.
+
+ para_server -l info
+
+Now you can use para_client to connect to the server and issue
+commands. Open a new shell as bar@client_host and try
+
+ para_client help
+ para_client si
+
+to retrieve the list of available commands and some server info.
+Don't proceed if this doesn't work.
+
+### Create and populate the database ###
+
+An empty database is created with
+
+ para_client init
+
+This initializes a couple of empty tables under
+~/.paraslash/afs_database-0.4. You normally don't need to look at these
+tables, but it's good to know that you can start from scratch with
+
+ rm -rf ~/.paraslash/afs_database-0.4
+
+in case something went wrong.
+
+Next, you need to add some audio files to that database so that
+para_server knows about them. Choose an absolute path to a directory
+containing some audio files and add them to the audio file table:
+
+ para_client add /my/mp3/dir
+
+This might take a while, so it is a good idea to start with a directory
+containing not too many files. Note that the table only contains data
+about the audio files found, not the files themselves.
+
+You may print the list of all known audio files with
+
+ para_client ls
+
+### Configure para_audiod ###
+
+We will have to tell para_audiod that it should receive the audio
+stream from server_host via http:
+
+ para_audiod -l info -r '.:http -i server_host'
+
+You should now be able to listen to the audio stream once para_server
+starts streaming. To activate streaming, execute
+
+ para_client play
+
+Since no playlist has been specified yet, the "dummy" mode which
+selects all known audio files is activated automatically. See the
+section on the [audio file selector](#The.audio.file.selector) for how
+to use playlists and moods to specify which files should be streamed
+in which order.
+
+Troubleshooting
+---------------
+
+If you receive a socket related error on server or audiod startup,
+make sure you have write permissions to the /var/paraslash directory:
+
+ sudo chown $LOGNAME /var/paraslash
+
+Alternatively, use the --afs-socket (para_server) or --socket
+(para_audiod) option to specify a different socket pathname.
+
+To identify streaming problems try to receive, decode and play the
+stream manually using para_recv, para_filter and para_write as follows.
+For simplicity we assume that you're running Linux/ALSA and that only
+MP3 files have been added to the database.
+
+ para_recv -r 'http -i server_host' > file.mp3
+ # (interrupt with CTRL+C after a few seconds)
+ ls -l file.mp3 # should not be empty
+ para_filter -f mp3dec -f wav < file.mp3 > file.wav
+ ls -l file.wav # should be much bigger than file.mp3
+ para_write -w alsa < file.wav
+
+Double check what is logged by para_server and use the --loglevel
+option of para_recv, para_filter and para_write to increase verbosity.
+
+===============
+User management
+===============
+
+para_server uses a challenge-response mechanism to authenticate
+requests from incoming connections, similar to ssh's public key
+authentication method. Authenticated connections are encrypted using
+a stream cipher, either RC4 or AES in integer counter mode.
+
+In this chapter we briefly describe RSA, RC4 and AES, and sketch the
+[authentication handshake](#Client-server.authentication)
+between para_client and para_server. User management is discussed
+in the section on [the user_list file](#The.user_list.file).
+These sections are all about communication between the client and the
+server. Connecting para_audiod is a different matter and is described
+in a [separate section](#Connecting.para_audiod).
+
+RSA, RC4, AES
+-------------
+
+RSA is an asymmetric block cipher which is used in many applications,
+including ssh and gpg. An RSA key consists in fact of two keys,
+called the public key and the private key. A message can be encrypted
+with either key and only the counterpart of that key can decrypt
+the message. While RSA can be used for both signing and encrypting
+a message, paraslash uses RSA only for the latter purpose. The
+RSA public key encryption and signatures algorithms are defined in
+detail in RFC 2437.
+
+RC4 is a stream cipher, i.e. the input is XORed with a pseudo-random
+key stream to produce the output. Decryption uses the same function
+calls as encryption. While RC4 supports variable key lengths,
+paraslash uses a fixed length of 256 bits, which is considered a
+strong encryption by today's standards. Since the same key must never
+be used twice, a different, randomly-generated key is used for every
+new connection.
+
+AES, the advanced encryption standard, is a well-known symmetric block
+cipher, i.e. a transformation operating on fixed-length blocks which
+is determined by a single key for both encryption and decryption. Any
+block cipher can be turned into a stream cipher by generating
+a pseudo-random key stream by encrypting successive values of a
+counter. The AES_CTR128 stream cipher used in paraslash is obtained
+in this way from the AES block cipher with a 128 bit block size.
+
+Client-server authentication
+----------------------------
+
+The authentication handshake between para_client and para_server goes
+as follows:
+
+- para_client connects to para_server and sends an authentication
+request for a user. It does so by connecting to TCP port 2990 of the
+server host. This port is called the para_server _control port_.
+
+- para_server accepts the connection and forks a child process which
+handles the incoming request. The parent process keeps listening on the
+control port while the child process (also called para_server below)
+continues as follows.
+
+- para_server loads the RSA public key of that user, fills a
+fixed-length buffer with random bytes, encrypts that buffer using the
+public key and sends the encrypted buffer to the client. The first
+part of the buffer is the challenge which is used for authentication
+while the second part is the session key.
+
+- para_client receives the encrypted buffer and decrypts it with the
+user's private key, thereby obtaining the challenge buffer and the
+session key. It sends the SHA1 hash value of the challenge back to
+para_server and stores the session key for further use.
+
+- para_server also computes the SHA1 hash of the challenge and compares
+it against what was sent back by the client.
+
+- If the two hashes do not match, the authentication has failed and
+para_server closes the connection.
+
+- Otherwise the user is considered authenticated and the client is
+allowed to proceed by sending a command to be executed. From this
+point on the communication is encrypted using the stream cipher with
+the session key known to both peers.
+
+paraslash relies on the quality of the pseudo-random bytes provided
+by the crypto library (openssl or libgcrypt), on the security of the
+implementation of the RSA, RC4 and AES crypto routines and on the
+infeasibility to invert the SHA1 function.
+
+Neither para_server or para_client create RSA keys on their
+own. This has to be done once for each user as sketched in
+[Quick start](#Quick.start) and discussed in more detail
+[below](#The.user_list.file).
+
+The user_list file
+------------------
+
+At startup para_server reads the user list file which contains one
+line per user. The default location of the user list file may be
+changed with the --user-list option.
+
+There should be at least one user in this file. Each user must have
+an RSA key pair. The public part of the key is needed by para_server
+while the private key is needed by para_client. Each line of the
+user list file must be of the form
+
+ user <username> <key> <perms>
+
+where _username_ is an arbitrary string (usually the user's login
+name), _key_ is the full path to that user's public RSA key, and
+_perms_ is a comma-separated list of zero or more of the following
+permission bits:
+
+ +---------------------------------------------------------+
+ | AFS_READ | read the contents of the databases |
+ +-----------+---------------------------------------------+
+ | AFS_WRITE | change database contents |
+ +-----------+---------------------------------------------+
+ | VSS_READ | obtain information about the current stream |
+ +-----------+---------------------------------------------+
+ | VSS_WRITE | change the current stream |
+ +---------------------------------------------------------+
+
+The permission bits specify which commands the user is allowed to
+execute. The output of
+
+ para_client help
+
+contains in the third column the permissions needed to execute the
+command.
+
+It is possible to make para_server reread the user_list file by
+executing the paraslash "hup" command or by sending SIGHUP to the
+PID of para_server.
+
+Connecting para_audiod
+----------------------
+
+para_audiod listens on a Unix domain socket. Those sockets are
+for local communication only, so only local users can connect to
+para_audiod. The default is to let any user connect but this can be
+restricted on platforms that support UNIX socket credentials which
+allow para_audiod to obtain the Unix credentials of the connecting
+process.
+
+Use para_audiod's --user-allow option to allow connections only for
+a limited set of users.
+
+=======================
+The audio file selector
+=======================
+
+paraslash comes with a sophisticated audio file selector (AFS),
+whose main task is to determine which file to stream next, based on
+information on the audio files stored in a database. It communicates
+also with para_client whenever an AFS command is executed, for example
+to answer a database query.
+
+Besides the traditional playlists, AFS supports audio file selection
+based on _moods_ which act as a filter that limits the set of all
+known audio files to those which satisfy certain criteria. It also
+maintains tables containing images (e.g. album cover art) and lyrics
+that can be associated with one or more audio files.
+
+AFS employs [libosl](http://people.tuebingen.mpg.de/maan/osl/), the
+object storage layer library, as the backend library for storing
+information on audio files, playlists, etc. This library offers
+functionality similar to a relational database, but is much more
+lightweight than a full database backend.
+
+In this chapter we sketch the setup of the [AFS
+process](#The.AFS.process) during server startup and proceed with the
+description of the [layout](#Database.layout) of the various database
+tables. The section on [playlists and moods](#Playlists.and.moods)
+explains these two audio file selection mechanisms in detail
+and contains pratical examples. The way [file renames and content
+changes](#File.renames.and.content.changes) are detected is discussed
+briefly before the [Troubleshooting](#Troubleshooting) section
+concludes the chapter.
+
+The AFS process
+---------------
+
+On startup, para_server forks to create the AFS process which opens
+the OSL database tables. The server process communicates with the
+AFS process via pipes and shared memory. Usually, the AFS process
+awakes only briefly whenever the current audio file changes. The AFS
+process determines the next audio file, opens it, verifies it has
+not been changed since it was added to the database and passes the
+open file descriptor to the server process, along with audio file
+meta-data such as file name, duration, audio format and so on. The
+server process then starts to stream the audio file.
+
+The AFS process also accepts connections from local clients via
+a well-known socket. However, only child processes of para_server
+may connect through this socket. All server commands that have the
+AFS_READ or AFS_WRITE permission bits use this mechanism to query or
+change the database.
+
+Database layout
+---------------
+
+### The audio file table ###
+
+This is the most important and usually also the largest table of the
+AFS database. It contains the information needed to stream each audio
+file. In particular the following data is stored for each audio file.
+
+- SHA1 hash value of the audio file contents. This is computed once
+when the file is added to the database. Whenever AFS selects this
+audio file for streaming the hash value is recomputed and checked
+against the value stored in the database to detect content changes.
+
+- The time when this audio file was last played.
+
+- The number of times the file has been played so far.
+
+- The attribute bitmask.
+
+- The image id which describes the image associated with this audio
+file.
+
+- The lyrics id which describes the lyrics associated with this
+audio file.
+
+- The audio format id (MP3, OGG, ...).
+
+- An amplification value that can be used by the amplification filter
+to pre-amplify the decoded audio stream.
+
+- The chunk table. It describes the location and the timing of the
+building blocks of the audio file. This is used by para_server to
+send chunks of the file at appropriate times.
+
+- The duration of the audio file.
+
+- Tag information contained in the audio file (ID3 tags, Vorbis
+comments, ...).
+
+- The number of channels
+
+- The encoding bitrate.
+
+- The sampling frequency.
+
+To add or refresh the data contained in the audio file table, the _add_
+command is used. It takes the full path of either an audio file or a
+directory. In the latter case, the directory is traversed recursively
+and all files which are recognized as valid audio files are added to
+the database.
+
+### The attribute table ###
+
+The attribute table contains two columns, _name_ and _bitnum_. An
+attribute is simply a name for a certain bit number in the attribute
+bitmask of the audio file table.
+
+Each of the 64 bits of the attribute bitmask can be set for each
+audio file individually. Hence up to 64 different attributes may be
+defined. For example, "pop", "rock", "blues", "jazz", "instrumental",
+"german_lyrics", "speech", whatever. You are free to choose as
+many attributes as you like and there are no naming restrictions
+for attributes.
+
+A new attribute "test" is created by
+
+ para_client addatt test
+and
+ para_client lsatt
+
+lists all available attributes. You can set the "test" attribute for
+an audio file by executing
+
+ para_client setatt test+ /path/to/the/audio/file
+
+Similarly, the "test" bit can be removed from an audio file with
+
+ para_client setatt test- /path/to/the/audio/file
+
+Instead of a path you may use a shell wildcard pattern. The attribute
+is applied to all audio files matching this pattern:
+
+ para_client setatt test+ '/test/directory/*'
+
+The command
+
+ para_client -- ls -l=v
+
+gives you a verbose listing of your audio files also showing which
+attributes are set.
+
+In case you wonder why the double-dash in the above command is needed:
+It tells para_client to not interpret the options after the dashes. If
+you find this annoying, just say
+
+ alias para='para_client --'
+
+and be happy. In what follows we shall use this alias.
+
+The "test" attribute can be dropped from the database with
+
+ para rmatt test
+
+Read the output of
+
+ para help ls
+ para help setatt
+
+for more information and a complete list of command line options to
+these commands.
+
+### Blob tables ###
+
+The image, lyrics, moods and playlists tables are all blob tables.
+Blob tables consist of three columns each: The identifier which is
+a positive non-negative number that is auto-incremented, the name
+(an arbitrary string) and the content (the blob).
+
+All blob tables support the same set of actions: cat, ls, mv, rm
+and add. Of course, _add_ is used for adding new blobs to the table
+while the other actions have the same meaning as the corresponding
+Unix commands. The paraslash commands to perform these actions are
+constructed as the concatenation of the table name and the action. For
+example addimg, catimg, lsimg, mvimg, rmimg are the commands that
+manipulate or query the image table.
+
+The add variant of these commands is special as these commands read
+the blob contents from stdin. To add an image to the image table the
+command
+
+ para addimg image_name < file.jpg
+
+can be used.
+
+Note that the images and lyrics are not interpreted at all, and also
+the playlist and the mood blobs are only investigated when the mood
+or playlist is activated with the select command.
+
+### The score table ###
+
+Unlike all other tables the contents of the score table remain in
+memory and are never stored on disk. The score table contains two
+columns: The SHA1 hash value (of an audio file) and its current
+score.
+
+However, only those files which are admissible for the current mood
+or playlist are contained in the score table. The audio file selector
+always chooses the row with the highest score as the file to stream
+next. While doing so, it computes the new score and updates the
+last_played and the num_played fields in the audio file table.
+
+The score table is recomputed by the select command which loads a
+mood or playlist. Audio files are chosen for streaming from the rows
+of the score table on a highest-score-first basis.
+
+
+Playlists and moods
+-------------------
+
+Playlists and moods offer two different ways of specifying the set of
+admissible files. A playlist in itself describes a set of admissible
+files. A mood, in contrast, describes the set of admissible files in
+terms of attributes and other type of information available in the
+audio file table. As an example, a mood can define a filename pattern,
+which is then matched against the names of audio files in the table.
+
+### Playlists ###
+
+Playlists are accommodated in the playlist table of the afs database,
+using the aforementioned blob format for tables. A new playlist is
+created with the addpl command by specifying the full (absolute)
+paths of all desired audio files, separated by newlines. Example:
+
+ find /my/mp3/dir -name "*.mp3" | para addpl my_playlist
+
+If _my_playlist_ already exists it is overwritten. To activate the
+new playlist, execute
+
+ para select p/my_playlist
+
+The audio file selector will assign scores to each entry of the list,
+in descending order so that files will be selected in order. If a
+file could not be opened for streaming, its entry is removed from
+the score table (but not from the playlist).
+
+### Moods ###
+
+A mood consists of a unique name and its *mood definition*, which is
+a set of *mood lines* containing expressions in terms of attributes
+and other data contained in the database.
+
+At any time at most one mood can be *active* which means that
+para_server is going to select only files from that subset of
+admissible files.
+
+So in order to create a mood definition one has to write a set of
+mood lines. Mood lines come in three flavours: Accept lines, deny
+lines and score lines.
+
+The general syntax of the three types of mood lines is
+
+
+ accept [with score <score>] [if] [not] <mood_method> [options]
+ deny [with score <score>] [if] [not] <mood_method> [options]
+ score <score> [if] [not] <mood_method> [options]
+
+
+Here <score> is either an integer or the string "random" which assigns
+a random score to all matching files. The score value changes the
+order in which admissible files are going to be selected, but is of
+minor importance for this introduction.
+
+So we concentrate on the first two forms, i.e. accept and deny
+lines. As usual, everything in square brackets is optional, i.e.
+accept/deny lines take the following form when ignoring scores:
+
+ accept [if] [not] <mood_method> [options]
+
+and analogously for the deny case. The "if" keyword is only syntactic
+sugar and has no function. The "not" keyword just inverts the result,
+so the essence of a mood line is the mood method part and the options
+following thereafter.
+
+A *mood method* is realized as a function which takes an audio file
+and computes a number from the data contained in the database.
+If this number is non-negative, we say the file *matches* the mood
+method. The file matches the full mood line if it either
+
+ - matches the mood method and the "not" keyword is not given,
+or
+ - does not match the mood method, but the "not" keyword is given.
+
+The set of admissible files for the whole mood is now defined as those
+files which match at least one accept mood line, but no deny mood line.
+More formally, an audio file F is admissible if and only if
+
+ (F ~ AL1 or F ~ AL2...) and not (F ~ DL1 or F ~ DN2 ...)
+
+where AL1, AL2... are the accept lines, DL1, DL2... are the deny
+lines and "~" means "matches".
+
+The cases where no mood lines of accept/deny type are defined need
+special treatment:
+
+ - Neither accept nor deny lines: This treats all files as
+ admissible (in fact, that is the definition of the dummy mood
+ which is activated automatically if no moods are available).
+
+ - Only accept lines: A file is admissible iff it matches at
+ least one accept line:
+
+ F ~ AL1 or F ~ AL2 or ...
+
+ - Only deny lines: A file is admissible iff it matches no
+ deny line:
+
+ not (F ~ DL1 or F ~ DN2 ...)
+
+
+
+### List of mood_methods ###
+
+ no_attributes_set
+
+Takes no arguments and matches an audio file if and only if no
+attributes are set.
+
+ is_set <attribute_name>
+
+Takes the name of an attribute and matches iff that attribute is set.
+
+ path_matches <pattern>
+
+Takes a filename pattern and matches iff the path of the audio file
+matches the pattern.
+
+ artist_matches <pattern>
+ album_matches <pattern>
+ title_matches <pattern>
+ comment_matches <pattern>
+
+Takes an extended regular expression and matches iff the text of the
+corresponding tag of the audio file matches the pattern. If the tag
+is not set, the empty string is matched against the pattern.
+
+ year ~ <num>
+ bitrate ~ <num>
+ frequency ~ <num>
+ channels ~ <num>
+ num_played ~ <num>
+
+Takes a comparator ~ of the set {<, =, <=, >, >=, !=} and a number
+<num>. Matches an audio file iff the condition <val> ~ <num> is
+satisfied where val is the corresponding value of the audio file
+(value of the year tag, bitrate in kbit/s, frequency in Hz, channel
+count, play count).
+
+The year tag is special as its value is undefined if the audio file
+has no year tag or the content of the year tag is not a number. Such
+audio files never match. Another difference is the special treatment
+if the year tag is a two-digit number. In this case either 1900 or
+2000 is added to the tag value, depending on whether the number is
+greater than 2000 plus the current year.
+
+
+### Mood usage ###
+
+To create a new mood called "my_mood", write its definition into
+some temporary file, say "tmpfile", and add it to the mood table
+by executing
+
+ para addmood my_mood < tmpfile
+
+If the mood definition is really short, you may just pipe it to the
+client instead of using temporary files. Like this:
+
+ echo "$MOOD_DEFINITION" | para addmood my_mood
+
+There is no need to keep the temporary file since you can always use
+the catmood command to get it back:
+
+ para catmood my_mood
+
+A mood can be activated by executing
+
+ para select m/my_mood
+
+Once active, the list of admissible files is shown by the ls command
+if the "-a" switch is given:
+
+ para ls -a
+
+
+### Example mood definition ###
+
+Suppose you have defined attributes "punk" and "rock" and want to define
+a mood containing only Punk-Rock songs. That is, an audio file should be
+admissible if and only if both attributes are set. Since
+
+ punk and rock
+
+is obviously the same as
+
+ not (not punk or not rock)
+
+(de Morgan's rule), a mood definition that selects only Punk-Rock
+songs is
+
+ deny if not is_set punk
+ deny if not is_set rock
+
+
+
+File renames and content changes
+--------------------------------
+
+Since the audio file selector knows the SHA1 of each audio file that
+has been added to the afs database, it recognizes if the content of
+a file has changed, e.g. because an ID3 tag was added or modified.
+Also, if a file has been renamed or moved to a different location,
+afs will detect that an entry with the same hash value already exists
+in the audio file table.
+
+In both cases it is enough to just re-add the new file. In the
+first case (file content changed), the audio table is updated, while
+metadata such as the num_played and last_played fields, as well as
+the attributes, remain unchanged. In the other case, when the file
+is moved or renamed, only the path information is updated, all other
+data remains as before.
+
+It is possible to change the behaviour of the add command by using the
+"-l" (lazy add) or the "-f" (force add) option.
+
+Troubleshooting
+---------------
+
+Use the debug loglevel (-l debug) to show debugging info. All paraslash
+executables have a brief online help which is displayed when -h is
+given. The --detailed-help option prints the full help text.
+
+If para_server crashed or was killed by SIGKILL (signal 9), it
+may refuse to start again because of "dirty osl tables". In this
+case you'll have to run the oslfsck program of libosl to fix your
+database:
+
+ oslfsck -fd ~/.paraslash/afs_database-0.4
+
+However, make sure para_server isn't running before executing oslfsck.
+
+If you don't mind to recreate your database you can start
+from scratch by removing the entire database directory, i.e.
+
+ rm -rf ~/.paraslash/afs_database-0.4
+
+Be aware that this removes all attribute definitions, all playlists
+and all mood definitions and requires to re-initialize the tables.
+
+Although oslfsck fixes inconsistencies in database tables it doesn't
+care about the table contents. To check for invalid table contents, use
+
+ para_client check
+
+This prints out references to missing audio files as well as invalid
+playlists and mood definitions.
+
+Similarly, para_audiod refuses to start if its socket file exists, since
+this indicates that another instance of para_audiod is running. After
+a crash a stale socket file might remain and you must run
+
+ para_audiod --force
+
+once to fix it up.
+
+=======================================
+Audio formats and audio format handlers
+=======================================
+
+Audio formats
+-------------
+
+The following audio formats are supported by paraslash:
+
+### MP3 ###
+
+Mp3, MPEG-1 Audio Layer 3, is a common audio format for audio storage,
+designed as part of its MPEG-1 standard. An MP3 file is made up of
+multiple MP3 frames, which consist of a header and a data block. The
+size of an MP3 frame depends on the bit rate and on the number
+of channels. For a typical CD-audio file (sample rate of 44.1 kHz
+stereo), encoded with a bit rate of 128 kbit, an MP3 frame is about
+400 bytes large.
+
+### OGG/Vorbis ###
+
+OGG is a standardized audio container format, while Vorbis is an
+open source codec for lossy audio compression. Since Vorbis is most
+commonly made available via the OGG container format, it is often
+referred to as OGG/Vorbis. The OGG container format divides data into
+chunks called OGG pages. A typical OGG page is about 4KB large. The
+Vorbis codec creates variable-bitrate (VBR) data, where the bitrate
+may vary considerably.
+
+### OGG/Speex ###
+
+Speex is an open-source speech codec that is based on CELP (Code
+Excited Linear Prediction) coding. It is designed for voice
+over IP applications, has modest complexity and a small memory
+footprint. Wideband and narrowband (telephone quality) speech are
+supported. As for Vorbis audio, Speex bit-streams are often stored
+in OGG files. As of 2012 this codec is considered obsolete since the
+Oppus codec, described below, surpasses its performance in all areas.
+
+### OGG/Opus ###
+
+Opus is a lossy audio compression format standardized through RFC
+6716 in 2012. It combines the speech-oriented SILK codec and the
+low-latency CELT (Constrained Energy Lapped Transform) codec. Like
+OGG/Vorbis and OGG/Speex, Opus data is usually encapsulated in OGG
+containers. All known software patents which cover Opus are licensed
+under royalty-free terms.
+
+### AAC ###
+
+Advanced Audio Coding (AAC) is a standardized, lossy compression
+and encoding scheme for digital audio which is the default audio
+format for Apple's iPhone, iPod, iTunes. Usually MPEG-4 is used as
+the container format and audio files encoded with AAC have the .m4a
+extension. A typical AAC frame is about 700 bytes large.
+
+### WMA ###
+
+Windows Media Audio (WMA) is an audio data compression technology
+developed by Microsoft. A WMA file is usually encapsulated in the
+Advanced Systems Format (ASF) container format, which also specifies
+how meta data about the file is to be encoded. The bit stream of WMA
+is composed of superframes, each containing one or more frames of
+2048 samples. For 16 bit stereo a WMA superframe is about 8K large.
+
+### FLAC ###
+
+The Free Lossless Audio Codec (FLAC) compresses audio without quality
+loss. It gives better compression ratios than a general purpose
+compressor like zip or bzip2 because FLAC is designed specifically
+for audio. A FLAC-encoded file consists of frames of varying size, up
+to 16K. Each frame starts with a header that contains all information
+necessary to decode the frame.
+
+Meta data
+---------
+
+Unfortunately, each audio format has its own conventions how meta
+data is added as tags to the audio file.
+
+For MP3 files, ID3, version 1 and 2 are widely used. ID3 version 1
+is rather simple but also very limited as it supports only artist,
+title, album, year and comment tags. Each of these can only be at most
+32 characters long. ID3, version 2 is much more flexible but requires
+a separate library being installed for paraslash to support it.
+
+Ogg vorbis, ogg speex and flac files contain meta data as Vorbis
+comments, which are typically implemented as strings of the form
+"[TAG]=[VALUE]". Unlike ID3 version 1 tags, one may use whichever
+tags are appropriate for the content.
+
+AAC files usually use the MPEG-4 container format for storing meta
+data while WMA files wrap meta data as special objects within the
+ASF container format.
+
+paraslash only tracks the most common tags that are supported by
+all tag variants: artist, title, year, album, comment. When a file
+is added to the AFS database, the meta data of the file is extracted
+and stored in the audio file table.
+
+Chunks and chunk tables
+-----------------------
+
+paraslash uses the word "chunk" as common term for the building blocks
+of an audio file. For MP3 files, a chunk is the same as an MP3 frame,
+while for OGG files a chunk is an OGG page, etc. Therefore the chunk
+size varies considerably between audio formats, from a few hundred
+bytes (MP3) up to 16K (FLAC).
+
+The chunk table contains the offsets within the audio file that
+correspond to the chunk boundaries of the file. Like the meta data,
+the chunk table is computed and stored in the database whenever an
+audio file is added.
+
+The paraslash senders (see below) always send complete chunks. The
+granularity for seeking is therefore determined by the chunk size.
+
+Audio format handlers
+---------------------
+
+For each audio format paraslash contains an audio format handler whose
+first task is to tell whether a given file is a valid audio file of
+this type. If so, the audio file handler extracts some technical data
+(duration, sampling rate, number of channels etc.), computes the
+chunk table and reads the meta data.
+
+The audio format handler code is linked into para_server and executed
+via the _add_ command. The same code is also available as a stand-alone
+tool, para_afh, which prints the technical data, the chunk table
+and the meta data of a file. Moreover, all audio format handlers are
+combined in the afh receiver which is part of para_recv and para_play.
+
+==========
+Networking
+==========
+
+Paraslash uses different network connections for control and data.
+para_client communicates with para_server over a dedicated TCP control
+connection. To transport audio data, separate data connections are
+used. For these data connections, a variety of transports (UDP, DCCP,
+HTTP) can be chosen.
+
+The chapter starts with the [control
+service](#The.paraslash.control.service), followed by a section
+on the various [streaming protocols](#Streaming.protocols)
+in which the data connections are described. The way
+audio file headers are embedded into the stream is discussed
+[briefly](#Streams.with.headers.and.headerless.streams) before the
+[example section](#Networking.examples) which illustrates typical
+commands for real-life scenarios.
+
+Both IPv4 and IPv6 are supported.
+
+The paraslash control service
+-----------------------------
+
+para_server is controlled at runtime via the paraslash control
+connection. This connection is used for server commands (play, stop,
+...) as well as for afs commands (ls, select, ...).
+
+The server listens on a TCP port and accepts connections from clients
+that connect the open port. Each connection causes the server to fork
+off a client process which inherits the connection and deals with that
+client only. In this classical accept/fork approach the server process
+is unaffected if the child dies or goes crazy for whatever reason. In
+fact, the child process can not change address space of server process.
+
+The section on [client-server
+authentication](#Client-server.authentication) above described the
+early connection establishment from the crypto point of view. Here
+it is described what happens after the connection (including crypto
+setup) has been established. There are four processes involved during
+command dispatch as sketched in the following diagram.
+
+ server_host client_host
+ ~~~~~~~~~~~ ~~~~~~~~~~~
+
+ +-----------+ connect +-----------+
+ |para_server|<------------------------------ |para_client|
+ +-----------+ +-----------+
+ | ^
+ | fork +---+ |
+ +----------> |AFS| |
+ | +---+ |
+ | ^ |
+ | | |
+ | | connect (cookie) |
+ | | |
+ | | |
+ | fork +-----+ inherited connection |
+ +---------->|child|<--------------------------+
+ +-----+
+
+Note that the child process is not a child of the afs process,
+so communication of these two processes has to happen via local
+sockets. In order to avoid abuse of the local socket by unrelated
+processes, a magic cookie is created once at server startup time just
+before the server process forks off the AFS process. This cookie is
+known to the server, AFS and the child, but not to unrelated processes.
+
+There are two different kinds of commands: First there are commands
+that cause the server to respond with some answer such as the list
+of all audio files. All but the addblob commands (addimg, addlyr,
+addpl, addmood) are of this kind. The addblob commands add contents
+to the database, so they need to transfer data the other way round,
+from the client to the server.
+
+There is no knowledge about the server commands built into para_client,
+so it does not know about addblob commands. Instead, the server sends
+a special "awaiting data" packet for these commands. If the client
+receives this packet, it sends STDIN to the server, otherwise it
+dumps data from the server to STDOUT.
+
+Streaming protocols
+-------------------
+
+A network (audio) stream usually consists of one streaming source,
+the _sender_, and one or more _receivers_ which read data over the
+network from the streaming source.
+
+Senders are thus part of para_server while receivers are part of
+para_audiod. Moreover, there is the stand-alone tool para_recv which
+can be used to manually download a stream, either from para_server
+or from a web-based audio streaming service.
+
+The following three streaming protocols are supported by paraslash:
+
+- HTTP. Recommended for public streams that can be played by any
+player like mpg123, xmms, itunes, winamp, etc. The HTTP sender is
+supported on all operating systems and all platforms.
+
+- DCCP. Recommended for LAN streaming. DCCP is currently available
+only for Linux.
+
+- UDP. Recommended for multicast LAN streaming.
+
+See the Appendix on [network protocols](/#Network.protocols)
+for brief descriptions of the various protocols relevant for network
+audio streaming with paraslash.
+
+It is possible to activate more than one sender simultaneously.
+Senders can be controlled at run time and via config file and command
+line options.
+
+Note that audio connections are _not_ encrypted. Transport or Internet
+layer encryption should be used if encrypted data connections are
+needed.
+
+Since DCCP and TCP are both connection-oriented protocols, connection
+establishment/teardown and access control are very similar between
+these two streaming protocols. UDP is the most lightweight option,
+since in contrast to TCP/DCCP it is connectionless. It is also the
+only protocol supporting IP multicast.
+
+The HTTP and the DCCP sender listen on a (TCP/DCCP) port waiting for
+clients to connect and establish a connection via some protocol-defined
+handshake mechanism. Both senders maintain two linked lists each:
+The list of all clients which are currently connected, and the list
+of access control entries which determines who is allowed to connect.
+IP-based access control may be configured through config file and
+command line options and via the "allow" and "deny" sender subcommands.
+
+Upon receiving a GET request from the client, the HTTP sender sends
+back a status line and a message. The body of this message is the
+audio stream. This is common practice and is supported by many popular
+clients which can thus be used to play a stream offered by para_server.
+For DCCP things are a bit simpler: No messages are exchanged between
+the receiver and sender. The client simply connects and the sender
+starts to stream.
+
+DCCP is an experimental protocol which offers a number of new features
+not available for TCP. Both ends can negotiate these features using
+a built-in negotiation mechanism. In contrast to TCP/HTTP, DCCP is
+datagram-based (no retransmissions) and thus should not be used over
+lossy media (e.g. WiFi networks). One useful feature offered by DCCP
+is access to a variety of different congestion-control mechanisms
+called CCIDs. Two different CCIDs are available per default on Linux:
+
+
+- _CCID 2_. A Congestion Control mechanism similar to that of TCP. The
+sender maintains a congestion window and halves this window in response
+to congestion.
+
+
+- _CCID-3_. Designed to be fair when competing for bandwidth.
+It has lower variation of throughput over time compared with TCP,
+which makes it suitable for streaming media.
+
+Unlike the HTTP and DCCP senders, the UDP sender maintains only a
+single list, the _target list_. This list describes the set of clients
+to which the stream is sent. There is no list for access control and
+no "allow" and "deny" commands for the UDP sender. Instead, the "add"
+and "delete" commands can be used to modify the target list.
+
+Since both UDP and DCCP offer an unreliable datagram-based transport,
+additional measures are necessary to guard against disruptions over
+networks that are lossy or which may be subject to interference (as
+is for instance the case with WiFi). Paraslash uses FEC (Forward
+Error Correction) to guard against packet losses and reordering. The
+stream is FEC-encoded before it is sent through the UDP socket and
+must be decoded accordingly on the receiver side.
+
+The packet size and the amount of redundancy introduced by FEC can
+be configured via the FEC parameters which are dictated by server
+and may also be configured through the "sender" command. The FEC
+parameters are encoded in the header of each network packet, so no
+configuration is necessary on the receiver side. See the section on
+[FEC](#Forward.error.correction) below.
+
+Streams with headers and headerless streams
+-------------------------------------------
+
+For OGG/Vorbis, OGG/Speex and wma streams, some of the information
+needed to decode the stream is only contained in the audio file
+header of the container format but not in each data chunk. Clients
+must be able to obtain this information in case streaming starts in
+the middle of the file or if para_audiod is started while para_server
+is already sending a stream.
+
+This is accomplished in different ways, depending on the streaming
+protocol. For connection-oriented streams (HTTP, DCCP) the audio file
+header is sent prior to audio file data. This technique however does
+not work for the connectionless UDP transport. Hence the audio file
+header is periodically being embedded into the UDP audio data stream.
+By default, the header is resent after five seconds. The receiver has
+to wait until the next header arrives before it can start decoding
+the stream.
+
+Networking examples
+-------------------
+
+The "si" (server info) command lists some information about the
+currently running server process.
+
+-> Show PIDs, number of connected clients, uptime, and more:
+
+ para_client si
+
+The sender command of para_server prints information about senders,
+like the various access control lists, and it allows to (de-)activate
+senders and to change the access permissions at runtime.
+
+-> List all senders
+
+ para_client sender
+
+-> Obtain general help for the sender command:
+
+ para_client help sender
+
+-> Get help for a specific sender (contains further examples):
+
+ s=http # or dccp or udp
+ para_client sender $s help
+
+-> Show status of the http sender
+
+ para_client sender http status
+
+By default para_server activates both the HTTP and th DCCP sender on
+startup. This can be changed via command line options or para_server's
+config file.
+
+-> List config file options for senders:
+
+ para_server -h
+
+All senders share the "on" and "off" commands, so senders may be
+activated and deactivated independently of each other.
+
+-> Switch off the http sender:
+
+ para_client sender http off
+
+-> Receive a DCCP stream using CCID2 and write the output into a file:
+
+ host=foo.org; ccid=2; filename=bar
+ para_recv --receiver "dccp --host $host --ccid $ccid" > $filename
+
+Note the quotes around the arguments for the dccp receiver. Each
+receiver has its own set of command line options and its own command
+line parser, so arguments for the dccp receiver must be protected
+from being interpreted by para_recv.
+
+-> Start UDP multicast, using the default multicast address:
+
+ para_client sender udp add 224.0.1.38
+
+-> Receive FEC-encoded multicast stream and write the output into a file:
+
+ filename=foo
+ para_recv -r udp > $filename
+
+-> Add an UDP unicast for a client to the target list of the UDP sender:
+
+ t=client.foo.org
+ para_client sender udp add $t
+
+-> Receive this (FEC-encoded) unicast stream:
+
+ filename=foo
+ para_recv -r 'udp -i 0.0.0.0' > $filename
+
+-> Create a minimal config for para_audiod for HTTP streams:
+
+ c=$HOME/.paraslash/audiod.conf.min; s=server.foo.com
+ echo receiver \".:http -i $s\" > $c
+ para_audiod --config $c
+
+=======
+Filters
+=======
+
+A paraslash filter is a module which transforms an input stream into
+an output stream. Filters are included in the para_audiod executable
+and in the stand-alone tool para_filter which usually contains the
+same modules.
+
+While para_filter reads its input stream from STDIN and writes
+the output to STDOUT, the filter modules of para_audiod are always
+connected to a receiver which produces the input stream and a writer
+which absorbs the output stream.
+
+Some filters depend on a specific library and are not compiled in
+if this library was not found at compile time. To see the list of
+supported filters, run para_filter and para_audiod with the --help
+option. The output looks similar to the following:
+
+ Available filters:
+ compress wav amp fecdec wmadec prebuffer oggdec aacdec mp3dec
+
+Out of these filter modules, a chain of filters can be constructed,
+much in the way Unix pipes can be chained, and analogous to the use
+of modules in gstreamer: The output of the first filter becomes the
+input of the second filter. There is no limitation on the number of
+filters and the same filter may occur more than once.
+
+Like receivers, each filter has its own command line options which
+must be quoted to protect them from the command line options of
+the driving application (para_audiod or para_filter). Example:
+
+ para_filter -f 'mp3dec --ignore-crc' -f 'compress --damp 1'
+
+For para_audiod, each audio format has its own set of filters. The
+name of the audio format for which the filter should be applied can
+be used as the prefix for the filter option. Example:
+
+ para_audiod -f 'mp3:prebuffer --duration 300'
+
+The "mp3" prefix above is actually interpreted as a POSIX extended
+regular expression. Therefore
+
+ para_audiod -f '.:prebuffer --duration 300'
+
+activates the prebuffer filter for all supported audio formats (because
+"." matches all audio formats) while
+
+ para_audiod -f 'wma|ogg:prebuffer --duration 300'
+
+activates it only for wma and ogg streams.
+
+Decoders
+--------
+
+For each supported audio format there is a corresponding filter
+which decodes audio data in this format to 16 bit PCM data which
+can be directly sent to the sound device or any other software that
+operates on undecoded PCM data (visualizers, equalizers etc.). Such
+filters are called _decoders_ in general, and xxxdec is the name of
+the paraslash decoder for the audio format xxx. For example, the mp3
+decoder is called mp3dec.
+
+Note that the output of the decoder is about 10 times larger than
+its input. This means that filters that operate on the decoded audio
+stream have to deal with much more data than filters that transform
+the audio stream before it is fed to the decoder.
+
+Paraslash relies on external libraries for most decoders, so these
+libraries must be installed for the decoder to be included in the
+executables. For example, the mp3dec filter depends on the mad library.
+
+Forward error correction
+------------------------
+
+As already mentioned [earlier](#Streaming.protocols), paraslash
+uses forward error correction (FEC) for the unreliable UDP and
+DCCP transports. FEC is a technique which was invented already in
+1960 by Reed and Solomon and which is widely used for the parity
+calculations of storage devices (RAID arrays). It is based on the
+algebraic concept of finite fields, today called Galois fields, in
+honour of the mathematician Galois (1811-1832). The FEC implementation
+of paraslash is based on code by Luigi Rizzo.
+
+Although the details require a sound knowledge of the underlying
+mathematics, the basic idea is not hard to understand: For positive
+integers k and n with k < n it is possible to compute for any k given
+data bytes d_1, ..., d_k the corresponding r := n -k parity bytes p_1,
+..., p_r such that all data bytes can be reconstructed from *any*
+k bytes of the set
+
+ {d_1, ..., d_k, p_1, ..., p_r}.
+
+FEC-encoding for unreliable network transports boils down to slicing
+the audio stream into groups of k suitably sized pieces called _slices_
+and computing the r corresponding parity slices. This step is performed
+in para_server which then sends both the data and the parity slices
+over the unreliable network connection. If the client was able
+to receive at least k of the n = k + r slices, it can reconstruct
+(FEC-decode) the original audio stream.
+
+From these observations it is clear that there are three different
+FEC parameters: The slice size, the number of data slices k, and the
+total number of slices n. It is crucial to choose the slice size
+such that no fragmentation of network packets takes place because
+FEC only guards against losses and reordering but fails if slices are
+received partially.
+
+FEC decoding in paralash is performed through the fecdec filter which
+usually is the first filter (there can be other filters before fecdec
+if these do not alter the audio stream).
+
+Volume adjustment (amp and compress)
+------------------------------------
+
+The amp and the compress filter both adjust the volume of the audio
+stream. These filters operate on uncompressed audio samples. Hence
+they are usually placed directly after the decoding filter. Each
+sample is multiplied with a scaling factor (>= 1) which makes amp
+and compress quite expensive in terms of computing power.
+
+### amp ###
+
+The amp filter amplifies the audio stream by a fixed scaling factor
+that must be known in advance. For para_audiod this factor is derived
+from the amplification field of the audio file's entry in the audio
+file table while para_filter uses the value given at the command line.
+
+The optimal scaling factor F for an audio file is the largest real
+number F >= 1 such that after multiplication with F all samples still
+fit into the sample interval [-32768, 32767]. One can use para_filter
+in combination with the sox utility to compute F:
+
+ para_filter -f mp3dec -f wav < file.mp3 | sox -t wav - -e stat -v
+
+The amplification value V which is stored in the audio file table,
+however, is an integer between 0 and 255 which is connected to F
+through the formula
+
+ V = (F - 1) * 64.
+
+To store V in the audio file table, the command
+
+ para_client -- touch -a=V file.mp3
+
+is used. The reader is encouraged to write a script that performs
+these computations :)
+
+### compress ###
+
+Unlike the amplification filter, the compress filter adjusts the volume
+of the audio stream dynamically without prior knowledge about the peak
+value. It maintains the maximal volume of the last n samples of the
+audio stream and computes a suitable amplification factor based on that
+value and the various configuration options. It tries to chose this
+factor such that the adjusted volume meets the desired target level.
+
+Note that it makes sense to combine amp and compress.
+
+Misc filters (wav and prebuffer)
+--------------------------------
+
+These filters are rather simple and do not modify the audio stream at
+all. The wav filter is only useful with para_filter and in connection
+with a decoder. It asks the decoder for the number of channels and the
+sample rate of the stream and adds a Microsoft wave header containing
+this information at the beginning. This allows to write wav files
+rather than raw PCM files (which do not contain any information about
+the number of channels and the sample rate).
+
+The prebuffer filter simply delays the output until the given time has
+passed (starting from the time the first byte was available in its
+input queue) or until the given amount of data has accumulated. It
+is mainly useful for para_audiod if the standard parameters result
+in buffer underruns.
+
+Both filters require almost no additional computing time, even when
+operating on uncompressed audio streams, since data buffers are simply
+"pushed down" rather than copied.
+
+Examples
+--------
+
+-> Decode an mp3 file to wav format:
+
+ para_filter -f mp3dec -f wav < file.mp3 > file.wav
+
+-> Amplify a raw audio file by a factor of 1.5:
+
+ para_filter -f amp --amp 32 < foo.raw > bar.raw
+
+======
+Output
+======
+
+Once an audio stream has been received and decoded to PCM format,
+it can be sent to a sound device for playback. This part is performed
+by paraslash _writers_ which are described in this chapter.
+
+Writers
+-------
+
+A paraslash writer acts as a data sink that consumes but does not
+produce audio data. Paraslash writers operate on the client side and
+are contained in para_audiod and in the stand-alone tool para_write.
+
+The para_write program reads uncompressed audio data from STDIN. If
+this data starts with a wav header, sample rate, sample format and
+channel count are read from the header. Otherwise CD audio (44.1KHz
+16 bit little endian, stereo) is assumed but this can be overridden
+by command line options. para_audiod, on the other hand, obtains
+the sample rate and the number of channels from the decoder.
+
+Like receivers and filters, each writer has an individual set of
+command line options, and for para_audiod writers can be configured
+per audio format separately. It is possible to activate more than
+one writer for the same stream simultaneously.
+
+OS-dependent APIs
+-----------------
+
+Unfortunately, the various flavours of Unix on which paraslash
+runs on have different APIs for opening a sound device and starting
+playback. Hence for each such API there is a paraslash writer that
+can play the audio stream via this API.
+
+- *ALSA*. The _Advanced Linux Sound Architecture_ is only available on
+Linux systems. Although there are several mid-layer APIs in use by
+the various Linux distributions (ESD, Jack, PulseAudio), paraslash
+currently supports only the low-level ALSA API which is not supposed
+to be change. ALSA is very feature-rich, in particular it supports
+software mixing via its DMIX plugin. ALSA is the default writer on
+Linux systems.
+
+- *OSS*. The _Open Sound System_ is the only API on \*BSD Unixes and
+is also available on Linux systems, usually provided by ALSA as an
+emulation for backwards compatibility. This API is rather simple but
+also limited. For example only one application can open the device
+at any time. The OSS writer is activated by default on BSD Systems.
+
+- *OSX*. Mac OS X has yet another API called CoreAudio. The OSX writer
+for this API is only compiled in on such systems and is of course
+the default there.
+
+- *FILE*. The file writer allows to capture the audio stream and
+write the PCM data to a file on the file system rather than playing
+it through a sound device. It is supported on all platforms and is
+always compiled in.
+
+- *AO*. _Libao_ is a cross-platform audio library which supports a wide
+variety of platforms including PulseAudio (gnome), ESD (Enlightened
+Sound Daemon), AIX, Solaris and IRIX. The ao writer plays audio
+through an output plugin of libao.
+
+Examples
+--------
+
+-> Use the OSS writer to play a wav file:
+
+ para_write --writer oss < file.wav
+
+-> Enable ALSA software mixing for mp3 streams:
+
+ para_audiod --writer 'mp3:alsa -d plug:swmix'
+
+
+===
+Gui
+===
+
+para_gui executes an arbitrary command which is supposed to print
+status information to STDOUT. It then displays this information in
+a curses window. By default the command
+
+ para_audioc -- stat -p
+
+is executed, but this can be customized via the --stat-cmd option. In
+particular it possible to use
+
+ para_client -- stat -p
+
+to make para_gui work on systems on which para_audiod is not running.
+
+Key bindings
+------------
+
+It is possible to bind keys to arbitrary commands via custom
+key-bindings. Besides the internal keys which can not be changed (help,
+quit, loglevel, version...), the following flavours of key-bindings
+are supported:
+
+- external: Shutdown curses before launching the given command.
+Useful for starting other ncurses programs from within para_gui,
+e.g. aumix or dialog scripts. Or, use the mbox output format to write
+a mailbox containing one mail for each (admissible) file the audio
+file selector knows about. Then start mutt from within para_gui to
+browse your collection!
+
+- display: Launch the command and display its stdout in para_gui's
+bottom window.
+
+- para: Like display, but start "para_client <specified command>"
+instead of "<specified command>".
+
+The general form of a key binding is
+
+ key_map k:m:c
+
+which maps key k to command c using mode m. Mode may be x, d or p
+for external, display and paraslash commands, respectively.
+
+Themes
+------
+
+Currently there are only two themes for para_gui. It is easy, however,
+to add more themes. To create a new theme one has to define the
+position, color and geometry for for each status item that should be
+shown by this theme. See gui_theme.c for examples.
+
+The "." and "," keys are used to switch between themes.
+
+Examples
+--------
+
+-> Show server info:
+
+ key_map "i:p:si"
+
+-> Jump to the middle of the current audio file by pressing F5:
+
+ key_map "<F5>:p:jmp 50"
+
+-> vi-like bindings for jumping around:
+
+ key_map "l:p:ff 10"
+ key_map "h:p:ff 10-"
+ key_map "w:p:ff 60"
+ key_map "b:p:ff 60-"
+
+-> Print the current date and time:
+
+ key_map "D:d:date"
+
+-> Call other curses programs:
+
+ key_map "U:x:aumix"
+ key_map "!:x:/bin/bash"
+ key_map "^E:x:/bin/sh -c 'vi ~/.paraslash/gui.conf'"
+
+===========
+Development
+===========
+
+Tools
+-----
+
+In order to compile the sources from the git repository (rather than
+from tar balls) and for contributing non-trivial changes to the
+paraslash project, some additional tools should be installed on a
+developer machine.
+
+- [git](http://git.or.cz/). As described in more detail
+[below](#Git.branches), the git source code management tool is used for
+paraslash development. It is necessary for cloning the git repository
+and for getting updates.
+
+- [m4](ftp://ftp.gnu.org/pub/gnu/m4/). Some input files for gengetopt
+are generated from templates by the m4 macro processor.
+
+- [autoconf](ftp://ftp.gnu.org/pub/gnu/autoconf/) GNU autoconf creates
+the configure file which is shipped in the tarballs but has to be
+generated when compiling from git.
+
+- [discount](http://www.pell.portland.or.us/~orc/Code/discount). The
+HTML version of this manual and some of the paraslash web pages are
+written in the Markdown markup language and are translated into html
+with the converter of the *Discount* package.
+
+- [doxygen](http://www.stack.nl/~dimitri/doxygen/). The documentation
+of paraslash's C sources uses the doxygen documentation system. The
+conventions for documenting the source code is described in the
+[Doxygen section](#Doxygen).
+
+- [global](ftp://ftp.gnu.org/pub/gnu/global). This is used to generate
+browsable HTML from the C sources. It is needed by doxygen.
+
+Git branches
+------------
+
+Paraslash has been developed using the git source code management
+tool since 2006. Development is organized roughly in the same spirit
+as the git development itself, as described below.
+
+The following text passage is based on "A note from the maintainer",
+written by Junio C Hamano, the maintainer of git.
+
+There are four branches in the paraslash repository that track the
+source tree: "master", "maint", "next", and "pu".
+
+The "master" branch is meant to contain what is well tested and
+ready to be used in a production setting. There could occasionally be
+minor breakages or brown paper bag bugs but they are not expected to
+be anything major, and more importantly quickly and easily fixable.
+Every now and then, a "feature release" is cut from the tip of this
+branch, named with three dotted decimal digits, like 0.4.2.
+
+Whenever changes are about to be included that will eventually lead to
+a new major release (e.g. 0.5.0), a "maint" branch is forked off from
+"master" at that point. Obvious, safe and urgent fixes after the major
+release are applied to this branch and maintenance releases are cut
+from it. New features never go to this branch. This branch is also
+merged into "master" to propagate the fixes forward.
+
+A trivial and safe enhancement goes directly on top of "master".
+New development does not usually happen on "master", however.
+Instead, a separate topic branch is forked from the tip of "master",
+and it first is tested in isolation; Usually there are a handful such
+topic branches that are running ahead of "master". The tip of these
+branches is not published in the public repository to keep the number
+of branches that downstream developers need to worry about low.
+
+The quality of topic branches varies widely. Some of them start out as
+"good idea but obviously is broken in some areas" and then with some
+more work become "more or less done and can now be tested by wider
+audience". Luckily, most of them start out in the latter, better shape.
+
+The "next" branch is to merge and test topic branches in the latter
+category. In general, this branch always contains the tip of "master".
+It might not be quite rock-solid production ready, but is expected to
+work more or less without major breakage. The maintainer usually uses
+the "next" version of paraslash for his own pleasure, so it cannot
+be _that_ broken. The "next" branch is where new and exciting things
+take place.
+
+The two branches "master" and "maint" are never rewound, and "next"
+usually will not be either (this automatically means the topics that
+have been merged into "next" are usually not rebased, and you can find
+the tip of topic branches you are interested in from the output of
+"git log next"). You should be able to safely build on top of them.
+
+However, at times "next" will be rebuilt from the tip of "master" to
+get rid of merge commits that will never be in "master". The commit
+that replaces "next" will usually have the identical tree, but it
+will have different ancestry from the tip of "master".
+
+The "pu" (proposed updates) branch bundles the remainder of the
+topic branches. The "pu" branch, and topic branches that are only in
+"pu", are subject to rebasing in general. By the above definition
+of how "next" works, you can tell that this branch will contain quite
+experimental and obviously broken stuff.
+
+When a topic that was in "pu" proves to be in testable shape, it
+graduates to "next". This is done with
+
+ git checkout next
+ git merge that-topic-branch
+
+Sometimes, an idea that looked promising turns out to be not so good
+and the topic can be dropped from "pu" in such a case.
+
+A topic that is in "next" is expected to be polished to perfection
+before it is merged to "master". Similar to the above, this is
+done with
+
+ git checkout master
+ git merge that-topic-branch
+ git branch -d that-topic-branch
+
+Note that being in "next" is not a guarantee to appear in the next
+release (being in "master" is such a guarantee, unless it is later
+found seriously broken and reverted), nor even in any future release.
+
+Coding Style
+------------
+
+The preferred coding style for paraslash coincides more or less
+with the style of the Linux kernel. So rather than repeating what is
+written [there](http://www.kernel.org/doc/Documentation/CodingStyle),
+here are the most important points.
+
+- Burn the GNU coding standards.
+- Never use spaces for indentation.
+- Tabs are 8 characters, and thus indentations are also 8 characters.
+- Don't put multiple assignments on a single line.
+- Avoid tricky expressions.
+- Don't leave whitespace at the end of lines.
+- The limit on the length of lines is 80 columns.
+- Use K&R style for placing braces and spaces:
+
+ if (x is true) {
+ we do y
+ }
+
+- Use a space after (most) keywords.
+- Do not add spaces around (inside) parenthesized expressions.
+- Use one space around (on each side of) most binary and ternary operators.
+- Do not use cute names like ThisVariableIsATemporaryCounter, call it tmp.
+- Mixed-case names are frowned upon.
+- Descriptive names for global variables are a must.
+- Avoid typedefs.
+- Functions should be short and sweet, and do just one thing.
+- The number of local variables shouldn't exceed 10.
+- Gotos are fine if they improve readability and reduce nesting.
+- Don't use C99-style "// ..." comments.
+- Names of macros defining constants and labels in enums are capitalized.
+- Enums are preferred when defining several related constants.
+- Always use the paraslash wrappers for allocating memory.
+- If the name of a function is an action or an imperative.
+ command, the function should return an error-code integer
+ (<0 means error, >=0 means success). If the name is a
+ predicate, the function should return a "succeeded" boolean.
+
+Doxygen
+-------
+
+Doxygen is a documentation system for various programming
+languages. The API reference on the paraslash web page is generated
+by doxygen.
+
+It is more illustrative to look at the source code for examples than
+to describe the conventions in this manual, so we only describe which
+parts of the code need doxygen comments, but leave out details on
+documentation conventions.
+
+As a rule, only the public part of the C source is documented with
+Doxygen. This includes structures, defines and enumerations in header
+files as well as public (non-static) C functions. These should be
+documented completely. For example, each parameter and the return
+value of a public function should get a descriptive doxygen comment.
+
+No doxygen comments are necessary for static functions and for
+structures and enumerations in C files (which are used only within
+this file). This does not mean, however, that those entities need
+no documentation at all. Instead, common sense should be applied to
+document what is not obvious from reading the code.
+
+========
+Appendix
+========
+
+Network protocols
+-----------------
+
+### IP ###
+
+The _Internet Protocol_ is the primary networking protocol used for
+the Internet. All protocols described below use IP as the underlying
+layer. Both the prevalent IPv4 and the next-generation IPv6 variant
+are being deployed actively worldwide.
+
+### Connection-oriented and connectionless protocols ###
+
+Connectionless protocols differ from connection-oriented ones in
+that state associated with the sending/receiving endpoints is treated
+implicitly. Connectionless protocols maintain no internal knowledge
+about the state of the connection. Hence they are not capable of
+reacting to state changes, such as sudden loss or congestion on the
+connection medium. Connection-oriented protocols, in contrast, make
+this knowledge explicit. The connection is established only after
+a bidirectional handshake which requires both endpoints to agree
+on the state of the connection, and may also involve negotiating
+specific parameters for the particular connection. Maintaining an
+up-to-date internal state of the connection also in general means
+that the sending endpoints perform congestion control, adapting to
+qualitative changes of the connection medium.
+
+### Reliability ###
+
+In IP networking, packets can be lost, duplicated, or delivered
+out of order, and different network protocols handle these
+problems in different ways. We call a transport-layer protocol
+_reliable_, if it turns the unreliable IP delivery into an ordered,
+duplicate- and loss-free delivery of packets. Sequence numbers
+are used to discard duplicates and re-arrange packets delivered
+out-of-order. Retransmission is used to guarantee loss-free
+delivery. Unreliable protocols, in contrast, do not guarantee ordering
+or data integrity.
+
+### Classification ###
+
+With these definitions the protocols which are used by paraslash for
+steaming audio data may be classified as follows.
+
+ - HTTP/TCP: connection-oriented, reliable,
+ - UDP: connectionless, unreliable,
+ - DCCP: connection-oriented, unreliable.
+
+Below we give a short descriptions of these protocols.
+
+### TCP ###
+
+The _Transmission Control Protocol_ provides reliable, ordered delivery
+of a stream and a classic window-based congestion control. In contrast
+to UDP and DCCP (see below), TCP does not have record-oriented or
+datagram-based syntax, i.e. it provides a stream which is unaware
+and independent of any record (packet) boundaries. TCP is used
+extensively by many application layers. Besides HTTP (the Hypertext
+Transfer Protocol), also FTP (the File Transfer protocol), SMTP (Simple
+Mail Transfer Protocol), SSH (Secure Shell) all sit on top of TCP.
+
+### UDP ###
+
+The _User Datagram Protocol_ is the simplest transport-layer protocol,
+built as a thin layer directly on top of IP. For this reason, it offers
+the same best-effort service as IP itself, i.e. there is no detection
+of duplicate or reordered packets. Being a connectionless protocol,
+only minimal internal state about the connection is maintained, which
+means that there is no protection against packet loss or network
+congestion. Error checking and correction (if at all) are performed
+in the application.
+
+### DCCP ###
+
+The _Datagram Congestion Control Protocol_ combines the
+connection-oriented state maintenance known from TCP with the
+unreliable, datagram-based transport of UDP. This means that it
+is capable of reacting to changes in the connection by performing
+congestion control, offering multiple alternative approaches. But it
+is bound to datagram boundaries (the maximum packet size supported
+by a medium), and like UDP it lacks retransmission to protect
+against loss. Due to the use of sequence numbers, it is however
+able to react to loss (interpreted as a congestion indication) and
+to ignore out-of-order and duplicate packets. Unlike TCP it allows
+to negotiate specific, binding features for a connection, such as
+the choice of congestion control: classic, window-based congestion
+control known from TCP is available as CCID-2, rate-based, "smooth"
+congestion control is offered as CCID-3.
+
+### HTTP ###
+
+The _Hypertext Transfer Protocol_ is an application layer protocol
+on top of TCP. It is spoken by web servers and is most often used
+for web services. However, as can be seen by the many Internet radio
+stations and YouTube/Flash videos, http is by far not limited to the
+delivery of web pages only. Being a simple request/response based
+protocol, the semantics of the protocol also allow the delivery of
+multimedia content, such as audio over http.
+
+### Multicast ###
+
+IP multicast is not really a protocol but a technique for one-to-many
+communication over an IP network. The challenge is to deliver
+information to a group of destinations simultaneously using the
+most efficient strategy to send the messages over each link of the
+network only once. This has benefits for streaming multimedia: the
+standard one-to-one unicast offered by TCP/DCCP means that n clients
+listening to the same stream also consume n-times the resources,
+whereas multicast requires to send the stream just once, irrespective
+of the number of receivers. Since it would be costly to maintain state
+for each listening receiver, multicast often implies connectionless
+transport, which is the reason that it is currently only available
+via UDP.
+
+Abstract socket namespace
+-------------------------
+UNIX domain sockets are a traditional way to communicate between
+processes on the same machine. They are always reliable (see above)
+and don't reorder datagrams. Unlike TCP and UDP, UNIX domain sockets
+support passing open file descriptors or process credentials to
+other processes.
+
+The usual way to set up a UNIX domain socket (as obtained from
+socket(2)) for listening is to first bind the socket to a file system
+pathname and then call listen(2), then accept(2). Such sockets are
+called _pathname sockets_ because bind(2) creates a special socket
+file at the specified path. Pathname sockets allow unrelated processes
+to communicate with the listening process by binding to the same path
+and calling connect(2).
+
+There are two problems with pathname sockets:
+
+ * The listing process must be able to (safely) create the
+ socket special in a directory which is also accessible to
+ the connecting process.
+
+ * After an unclean shutdown of the listening process, a stale
+ socket special may reside on the file system.
+
+The abstract socket namespace is a non-portable Linux feature which
+avoids these problems. Abstract sockets are still bound to a name,
+but the name has no connection with file system pathnames.
+
+License
+-------
+
+Paraslash is licensed under the GPL, version 2. Most of the code
+base has been written from scratch, and those parts are GPL V2
+throughout. Notable exceptions are FEC and the WMA decoder. See the
+corresponding source files for licencing details for these parts. Some
+code sniplets of several other third party software packages have
+been incorporated into the paraslash sources, for example log message
+coloring was taken from the git sources. These third party software
+packages are all published under the GPL or some other license
+compatible to the GPL.
+
+Acknowledgements
+----------------
+
+Many thanks to Gerrit Renker who read an early draft of this manual
+and contributed significant improvements.
+
+==========
+References
+==========
+
+Articles
+--------
+- [Polynomial Codes over Certain Finite
+Fields](http://kom.aau.dk/~heb/kurser/NOTER/KOFA01.PDF) by Reed, Irving
+S.; Solomon, Gustave (1960), Journal of the Society for Industrial
+and Applied Mathematics (SIAM) 8 (2): 300-304, doi:10.1137/0108018)
+
+RFCs
+----
+
+- [RFC 768](http://www.ietf.org/rfc/rfc768.txt) (1980): User Datagram
+Protocol
+
+- [RFC 791](http://www.ietf.org/rfc/rfc791.txt) (1981): Internet
+Protocol
+
+- [RFC 2437](http://www.ietf.org/rfc/rfc2437.txt) (1998): RSA
+Cryptography Specifications
+
+- [RFC 4340](http://www.ietf.org/rfc/rfc4340.txt) (2006): Datagram
+Congestion Control Protocol (DCCP)
+
+- [RFC 4341](http://www.ietf.org/rfc/rfc4341.txt) (2006): Congestion
+Control ID 2: TCP-like Congestion Control
+
+- [RFC 4342](http://www.ietf.org/rfc/rfc4342.txt) (2006): Congestion
+Control ID 3: TCP-Friendly Rate Control (TFRC)
+
+- [RFC 6716](http://www.ietf.org/rfc/rfc6716.txt) (2012): Definition
+of the Opus Audio Codec
+
+Application web pages
+---------------------
+
+- [paraslash](http://people.tuebingen.mpg.de/maan/paraslash/)
+- [alternative page](http://paraslash.systemlinux.org/)
+- [xmms](http://xmms2.org/wiki/Main_Page)
+- [mpg123](http://www.mpg123.de/)
+- [gstreamer](http://gstreamer.freedesktop.org/)
+- [icecast](http://www.icecast.org/)
+- [Audio Compress](http://beesbuzz.biz/code/audiocompress.php)
+
+External documentation
+----------------------
+
+- [The mathematics of
+Raid6](http://kernel.org/pub/linux/kernel/people/hpa/raid6.pdf)
+by H. Peter Anvin
+
+- [Effective Erasure Codes for reliable Computer Communication
+Protocols](http://info.iet.unipi.it/~luigi/fec_ccr.ps.gz) by Luigi
+Rizzo
+
+Code
+----
+- [Original FEC
+implementation](http://info.iet.unipi.it/~luigi/vdm.tar.gz) by
+Luigi Rizzo)
projects / paraslash.git / commitdiff