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Code Issues Releases Activity

mp3dec: read Xing frame TOC index

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This commit is contained in:
Anton Khirnov 2012-09-02 15:36:18 +02:00
parent 2d1a1a7f62
commit 50d1f4437b
1 changed files with 57 additions and 1 deletions
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58
libavformat/mp3dec.c
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@ -31,6 +31,9 @@
#define XING_FLAG_FRAMES 0x01
#define XING_FLAG_SIZE 0x02
#define XING_FLAG_TOC 0x04
#define XING_TOC_COUNT 100
/* mp3 read */
@ -94,6 +97,26 @@ static int mp3_read_probe(AVProbeData *p)
//mpegps_mp3_unrecognized_format.mpg has max_frames=3
}
static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
{
int i;
if (!filesize &&
!(filesize = avio_size(s->pb))) {
av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
return;
}
for (i = 0; i < XING_TOC_COUNT; i++) {
uint8_t b = avio_r8(s->pb);
av_add_index_entry(s->streams[0],
av_rescale(b, filesize, 256),
av_rescale(i, duration, XING_TOC_COUNT),
0, 0, AVINDEX_KEYFRAME);
}
}
/**
* Try to find Xing/Info/VBRI tags and compute duration from info therein
*/
@ -115,6 +138,8 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
if(c.layer != 3)
return -1;
spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
/* Check for Xing / Info tag */
avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
v = avio_rb32(s->pb);
@ -124,6 +149,9 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
frames = avio_rb32(s->pb);
if(v & XING_FLAG_SIZE)
size = avio_rb32(s->pb);
if (v & XING_FLAG_TOC && frames)
read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
st->time_base));
}
/* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
@ -145,7 +173,6 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
/* Skip the vbr tag frame */
avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
if(frames)
st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
st->time_base);
@ -206,12 +233,41 @@ static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
return ret;
}
static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
int flags)
{
AVIndexEntry *ie;
AVStream *st = s->streams[0];
int64_t ret = av_index_search_timestamp(st, timestamp, flags);
uint32_t header = 0;
if (ret < 0)
return ret;
ie = &st->index_entries[ret];
ret = avio_seek(s->pb, ie->pos, SEEK_SET);
if (ret < 0)
return ret;
while (!s->pb->eof_reached) {
header = (header << 8) + avio_r8(s->pb);
if (ff_mpa_check_header(header) >= 0) {
ff_update_cur_dts(s, st, ie->timestamp);
ret = avio_seek(s->pb, -4, SEEK_CUR);
return (ret >= 0) ? 0 : ret;
}
}
return AVERROR_EOF;
}
AVInputFormat ff_mp3_demuxer = {
.name = "mp3",
.long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
.read_probe = mp3_read_probe,
.read_header = mp3_read_header,
.read_packet = mp3_read_packet,
.read_seek = mp3_seek,
.flags = AVFMT_GENERIC_INDEX,
.extensions = "mp2,mp3,m2a", /* XXX: use probe */
};