From: Andre Noll <maan@systemlinux.org>
Date: Sun, 15 Mar 2009 16:35:37 +0000 (+0100)
Subject: alsa: Split alsa_open().
X-Git-Tag: v0.3.4~33
X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=90e7bf17d7b535c66887414baa5c2187822117c3;p=paraslash.git

alsa: Split alsa_open().

Only perform what is absolutely necessary in alsa_open(). Call the
real alsa initialization from alsa_post_select(), when we actually
have audio data available to start streaming.

This should get rid of the sound artefacts that happen sometimes
at the beginning of the stream.
---

diff --git a/alsa_write.c b/alsa_write.c
index dfd2421d..f63b7a5e 100644
--- a/alsa_write.c
+++ b/alsa_write.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2005-2008 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -51,33 +51,16 @@ struct private_alsa_write_data {
 	unsigned channels;
 };
 
-/*
- * open and prepare the PCM handle for writing
- *
- * Install PCM software and hardware configuration. Exit on errors.
- */
-static int alsa_open(struct writer_node *w)
+/* Install PCM software and hardware configuration. */
+static int alsa_init(struct private_alsa_write_data *pad,
+		struct alsa_write_args_info *conf)
 {
 	snd_pcm_hw_params_t *hwparams;
 	snd_pcm_sw_params_t *swparams;
 	snd_pcm_uframes_t buffer_size, start_threshold, stop_threshold;
-	int err;
 	snd_pcm_uframes_t period_size;
-	struct private_alsa_write_data *pad = para_calloc(sizeof(struct
-		private_alsa_write_data));
-	struct alsa_write_args_info *conf = w->conf;
-	struct writer_node_group *wng = w->wng;
+	int err;
 
-	if (!conf->samplerate_given && wng->samplerate)
-		pad->samplerate = *wng->samplerate;
-	else
-		pad->samplerate = conf->samplerate_arg;
-	if (!conf->channels_given && wng->channels)
-		pad->channels = *wng->channels;
-	else
-		pad->channels = conf->channels_arg;
-	PARA_INFO_LOG("%d channel(s), %dHz\n", pad->channels, pad->samplerate);
-	w->private_data = pad;
 	err = snd_pcm_open(&pad->handle, conf->device_arg,
 		SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
 	if (err < 0)
@@ -133,7 +116,27 @@ static int alsa_open(struct writer_node *w)
 	PARA_INFO_LOG("bytes per frame: %zu\n", pad->bytes_per_frame);
 	if (snd_pcm_nonblock(pad->handle, 1))
 		PARA_ERROR_LOG("failed to set nonblock mode\n");
-	tv_add(now, &(struct timeval ){0, 100 * 1000}, &pad->next_chunk);
+	return 1;
+}
+
+/* Open an instance of the alsa writer. */
+static int alsa_open(struct writer_node *wn)
+{
+	struct alsa_write_args_info *conf = wn->conf;
+	struct writer_node_group *wng = wn->wng;
+	struct private_alsa_write_data *pad = para_calloc(sizeof(*pad));
+
+	wn->private_data = pad;
+	if (!conf->samplerate_given && wng->samplerate)
+		pad->samplerate = *wng->samplerate;
+	else
+		pad->samplerate = conf->samplerate_arg;
+	if (!conf->channels_given && wng->channels)
+		pad->channels = *wng->channels;
+	else
+		pad->channels = conf->channels_arg;
+	PARA_INFO_LOG("%d channel(s), %dHz\n", pad->channels, pad->samplerate);
+	tv_add(now, &(struct timeval){0, 100 * 1000}, &pad->next_chunk);
 	return 1;
 }
 
@@ -143,7 +146,7 @@ static int alsa_write_pre_select(struct sched *s, struct writer_node *wn)
 	struct writer_node_group *wng = wn->wng;
 	struct timeval diff;
 
-	if (*wng->loaded < pad->bytes_per_frame)
+	if (!*wng->loaded)
 		return 1;
 	if (tv_diff(now, &pad->next_chunk, &diff) < 0) {
 		if (tv_diff(&s->timeout, &diff, NULL) > 0)
@@ -153,7 +156,6 @@ static int alsa_write_pre_select(struct sched *s, struct writer_node *wn)
 		s->timeout.tv_usec = 1;
 	}
 	return 1;
-//	PARA_INFO_LOG("timeout: %lu\n", tv2ms(&s->timeout));
 }
 
 static int alsa_write_post_select(__a_unused struct sched *s,
@@ -161,19 +163,21 @@ static int alsa_write_post_select(__a_unused struct sched *s,
 {
 	struct private_alsa_write_data *pad = wn->private_data;
 	struct writer_node_group *wng = wn->wng;
-	size_t frames = (*wng->loaded - wn->written) / pad->bytes_per_frame;
-	snd_pcm_sframes_t ret;
+	size_t frames, bytes = *wng->loaded - wn->written;
 	unsigned char *data = (unsigned char*)wng->buf + wn->written;
 	struct timeval tv;
+	snd_pcm_sframes_t ret;
 
-//	PARA_INFO_LOG("%zd frames\n", frames);
-	if (!frames) {
-		if (*wng->input_error)
-			wn->written = *wng->loaded;
-		return 1;
-	}
+	if (!bytes) /* no data available */
+		goto out;
 	if (tv_diff(now, &pad->next_chunk, NULL) < 0)
-		return 1;
+		goto out;
+	if (!pad->handle) {
+		int err = alsa_init(pad, wn->conf);
+		if (err < 0)
+			return err;
+	}
+	frames = bytes / pad->bytes_per_frame;
 	ret = snd_pcm_writei(pad->handle, data, frames);
 	if (ret == -EPIPE) {
 		PARA_WARNING_LOG("EPIPE\n");
@@ -195,6 +199,11 @@ static int alsa_write_post_select(__a_unused struct sched *s,
 		ms2tv(pad->buffer_time / pad->bytes_per_frame / 1000, &tv);
 		tv_add(now, &tv, &pad->next_chunk);
 	}
+out:
+	if (*wng->input_error < 0) {
+		wn->written = *wng->loaded;
+		return *wng->input_error;
+	}
 	return 1;
 }