path: root/opus_afh.c

/* SPDX-License-Identifier: GPL-2.0 */

/** \file opus_afh.c Audio format handler for ogg/opus files. */

#include <ogg/ogg.h>

#include "para.h"
#include "afh.h"
#include "error.h"
#include "portable_io.h"
#include "string.h"
#include "opus_common.h"
#include "ogg_afh_common.h"

static const char * const opus_suffixes[] = {"opus", NULL};

#define OPUS_COMMENT_HEADER "OpusTags"

static bool copy_if_tag_type(const char *tag, int taglen, const char *type,
		char **p)
{
	char *q = key_value_copy(tag, taglen, type);
	if (!q)
		return false;
	free(*p);
	*p = q;
	return true;
}

static int opus_get_comments(char *comments, int length,
		struct taginfo *tags)
{
	char *p = comments, *end = comments + length;
	int i;
	uint32_t val, ntags;

	/* min size of a opus header is 16 bytes */
	if (length < 16)
		return -E_OPUS_COMMENT;
	if (memcmp(p, OPUS_COMMENT_HEADER, strlen(OPUS_COMMENT_HEADER)) != 0)
		return -E_OPUS_COMMENT;
	p += 8;
	val = read_u32(p);
	p += 4;
	if (p + val > end)
		return -E_OPUS_COMMENT;
	tags->comment = safe_strdup(p, val);
	p += val;
	ntags = read_u32(p);
	p += 4;
	if (p + ntags * 4 > end)
		return -E_OPUS_COMMENT;
	PARA_INFO_LOG("found %u tag(s)\n", ntags);
	for (i = 0; i < ntags; i++, p += val) {
		char *tag;

		if (p + 4 > end)
			return -E_OPUS_COMMENT;
		val = read_u32(p);
		p += 4;
		if (p + val > end)
			return -E_OPUS_COMMENT;
		if (copy_if_tag_type(p, val, "author", &tags->artist))
			continue;
		if (copy_if_tag_type(p, val, "artist", &tags->artist))
			continue;
		if (copy_if_tag_type(p, val, "title", &tags->title))
			continue;
		if (copy_if_tag_type(p, val, "album", &tags->album))
			continue;
		if (copy_if_tag_type(p, val, "year", &tags->year))
			continue;
		if (copy_if_tag_type(p, val, "comment", &tags->comment))
			continue;
		tag = safe_strdup(p, val);
		PARA_NOTICE_LOG("unrecognized tag: %s\n", tag);
		free(tag);
	}
	return 1;
}

/*
 * Ogg/Opus has two mandatory header packets:
 *
 * 1. ID header (identifies the stream as Opus). Dedicated "BOS" ogg page.
 * 2. Comment header (metadata). May span multiple pages.
 *
 * See doc/draft-ietf-codec-oggopus.xml in the opus source tree for details.
 */
static int opus_packet_callback(ogg_packet *packet, int packet_num,
		__a_unused int serial, struct afh_info *afhi,
		void *private_data)
{
	int ret;
	struct opus_header *oh = private_data;

	if (packet_num == 0) {
		ret = opus_parse_header((char *)packet->packet, packet->bytes, oh);
		if (ret < 0)
			return ret;
		afhi->channels = oh->channels;
		afhi->techinfo = make_message(
			"header version %d, input sample rate: %" PRIu32 "Hz",
			oh->version, oh->input_sample_rate);
		/*
		 * The input sample rate is irrelevant for afhi->frequency as
		 * we always decode to 48kHz.
		 */
		afhi->frequency = 48000;
		return 1;
	}
	if (packet_num == 1) {
		ret = opus_get_comments((char *)packet->packet, packet->bytes,
			&afhi->tags);
		if (ret < 0)
			return ret;
		return 0; /* header complete */
	}
	/* never reached */
	assert(0);
}

static int opus_get_file_info(char *map, size_t numbytes, struct afh_info *afhi)
{
	int ret, ms;
	struct opus_header oh = {.version = 0};

	struct oac_callback_info opus_callback_info = {
		.packet_callback = opus_packet_callback,
		.private_data = &oh,
	};
	ret = oac_get_file_info(map, numbytes, afhi, &opus_callback_info);
	if (ret < 0)
		return ret;
	ret = (afhi->chunk_table[afhi->chunks_total] - afhi->chunk_table[0]) * 8; /* bits */
	ms = tv2ms(&afhi->chunk_tv) * afhi->chunks_total;
	afhi->bitrate = ret / ms;
	return 1;
}

static size_t opus_make_meta_packet(struct taginfo *tags, char **result)
{
	size_t sz;
	char *buf, *p;
	size_t comment_len = strlen(tags->comment),
		artist_len = strlen(tags->artist),
		title_len = strlen(tags->title),
		album_len = strlen(tags->album),
		year_len = strlen(tags->year);
	uint32_t comment_sz = comment_len,
		artist_sz = artist_len + strlen("artist="),
		title_sz = title_len + strlen("title="),
		album_sz = album_len + strlen("album="),
		year_sz = year_len + strlen("year=");
	uint32_t num_tags;

	sz = strlen(OPUS_COMMENT_HEADER)
		+ 4 /* comment length (always present) */
		+ comment_sz
		+ 4; /* number of tags */
	num_tags = 0;
	if (artist_len) {
		num_tags++;
		sz += 4 + artist_sz;
	}
	if (title_len) {
		num_tags++;
		sz += 4 + title_sz;
	}
	if (album_len) {
		num_tags++;
		sz += 4 + album_sz;
	}
	if (year_len) {
		num_tags++;
		sz += 4 + year_sz;
	}
	PARA_DEBUG_LOG("meta packet size: %zu bytes\n", sz);
	/* terminating zero byte for the last sprintf() */
	buf = p = alloc(sz + 1);
	memcpy(p, OPUS_COMMENT_HEADER, strlen(OPUS_COMMENT_HEADER));
	p += strlen(OPUS_COMMENT_HEADER);
	write_u32(p, comment_sz);
	p += 4;
	strcpy(p, tags->comment);
	p += comment_sz;
	write_u32(p, num_tags);
	p += 4;
	if (artist_len) {
		write_u32(p, artist_sz);
		p += 4;
		sprintf(p, "artist=%s", tags->artist);
		p += artist_sz;
	}
	if (title_len) {
		write_u32(p, title_sz);
		p += 4;
		sprintf(p, "title=%s", tags->title);
		p += title_sz;
	}
	if (album_len) {
		write_u32(p, album_sz);
		p += 4;
		sprintf(p, "album=%s", tags->album);
		p += album_sz;
	}
	if (year_len) {
		write_u32(p, year_sz);
		p += 4;
		sprintf(p, "year=%s", tags->year);
		p += year_sz;
	}
	assert(p == buf + sz);
	*result = buf;
	return sz;
}

static int opus_rewrite_tags(const char *map, size_t mapsize,
		struct taginfo *tags, int output_fd)
{
	char *meta_packet;
	size_t meta_sz;
	int ret;

	meta_sz = opus_make_meta_packet(tags, &meta_packet);
	ret = oac_rewrite_tags(map, mapsize, output_fd, meta_packet, meta_sz);
	free(meta_packet);
	return ret;
}

/*
 * See doc/draft-ietf-codec-oggopus.xml in the opus source tree for details
 * about the format of the comment header.
 */
static int opus_get_header_callback(ogg_packet *packet, int packet_num,
		int serial, __a_unused struct afh_info *afhi, void *private_data)
{
	struct oac_custom_header *h = private_data;
	int ret;
	static unsigned char dummy_tags[] = { /* a minimal comment header */
		'O', 'p', 'u', 's', 'T', 'a', 'g', 's',
		0x06, 0x00, 0x00, 0x00, /* vendor string length */
		'd', 'u', 'm', 'm', 'y', '\0', /* vendor string */
		0x00, 0x00, 0x00, 0x00, /* user comment list length */
	};
	ogg_packet replacement;

	if (packet_num == 0) {
		oac_custom_header_init(serial, h);
		ret = oac_custom_header_append(packet, h);
		if (ret < 0)
			return ret;
		oac_custom_header_flush(h);
		return 1;
	}
	assert(packet_num == 1);
	PARA_INFO_LOG("replacing metadata packet\n");
	replacement = *packet;
	replacement.packet = dummy_tags;
	replacement.bytes = sizeof(dummy_tags);
	ret = oac_custom_header_append(&replacement, h);
	if (ret < 0)
		return ret;
	oac_custom_header_flush(h);
	return 0;
}

static void opus_get_header(void *map, size_t mapsize, char **buf,
		size_t *len)
{
	int ret;
	struct oac_custom_header *h = oac_custom_header_new();
	struct oac_callback_info cb = {
		.packet_callback = opus_get_header_callback,
		.private_data = h,
	};

	ret = oac_get_file_info(map, mapsize, NULL, &cb);
	*len = oac_custom_header_get(buf, h);
	if (ret < 0) {
		PARA_ERROR_LOG("could not create custom header: %s\n",
			para_strerror(-ret));
		free(*buf);
		*buf = NULL;
		*len = 0;
	} else
		PARA_INFO_LOG("created %zu byte ogg/opus header\n", *len);
}

/**
 * The audio format handler for ogg/opus.
 *
 * The opus codec was standardized by the Internet Engineering Task Force and
 * is described in RFC 6716 (2012). The audio format handler depends on the ogg
 * and the opus libraries.
 */
const struct audio_format_handler opus_afh = {
	.get_file_info = opus_get_file_info,
	.get_header = opus_get_header,
	.suffixes = opus_suffixes,
	.rewrite_tags = opus_rewrite_tags,
};