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mp3 codec autodetection patch by (Andriy Rysin <arysin at bcsii dot net>) 

Originally committed as revision 1833 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Andriy Rysin 2003-05-05 10:56:23 +00:00 committed by Michael Niedermayer
parent eb14c71360
commit eeb67f400c
1 changed files with 14 additions and 0 deletions
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14
libavformat/raw.c
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@ -109,6 +109,7 @@ static int mp3_read_header(AVFormatContext *s,
AVFormatParameters *ap)
{
AVStream *st;
int pos;
st = av_new_stream(s, 0);
if (!st)
@ -116,6 +117,19 @@ static int mp3_read_header(AVFormatContext *s,
st->codec.codec_type = CODEC_TYPE_AUDIO;
st->codec.codec_id = CODEC_ID_MP2;
/* looking for 11111111 111MMLLC - MPEG synchronization tag
MM: 00 - MPEG-2.5, 10 - MPEG-2, 11 - MPEG-1
LL: 11 - Layer I, 10 - Layer II, 01 - Layer III
XXX: this code does not read more bytes from file
so if ID3 (or other stuff) length > IO_BUFFER_SIZE it fails back to CODEC_ID_MP2 */
for(pos=0; pos < s->pb.buffer_size-1; pos++)
if( s->pb.buffer[pos] == 0xFF && (s->pb.buffer[pos] & 0xE0) == 0xE0 )
break;
if( pos < s->pb.buffer_size-1 && (s->pb.buffer[pos+1] & 6) == 2 )
st->codec.codec_id = CODEC_ID_MP3LAME;
/* the parameters will be extracted from the compressed bitstream */
return 0;
}