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Allows the AC3 parser to read the frame size and codec parameters from E-AC3 streams,

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allowing them to be correctly demuxed.
Currently it only identifies the primary substream, and will skip over any additional
dependent or independent substreams.
Patch by Ian Caulfield % ian P caulfield A gmail P com %
Original thread:
date: Jan 19, 2007 9:55 AM
subject: Re: [Ffmpeg-devel] [PATCH] Correctly parse headers of E-AC3 streams

Originally committed as revision 7687 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Ian Caulfield 2007-01-24 15:31:48 +00:00 committed by Guillaume Poirier
parent 6ad7cd0469
commit 44a39bd770
1 changed files with 46 additions and 5 deletions
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51
libavcodec/parser.c
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@ -632,9 +632,14 @@ static const int ac3_bitrates[64] = {
384, 448, 448, 512, 512, 576, 576, 640, 640,
};
static const int ac3_channels[8] = {
static const uint8_t ac3_channels[8] = {
2, 1, 2, 3, 3, 4, 4, 5
};
static const uint8_t eac3_blocks[4] = {
1, 2, 3, 6
};
#endif /* CONFIG_AC3_PARSER */
#ifdef CONFIG_AAC_PARSER
@ -653,6 +658,7 @@ static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
int *bit_rate, int *samples)
{
unsigned int fscod, frmsizecod, acmod, bsid, lfeon;
unsigned int strmtyp, substreamid, frmsiz, fscod2, numblkscod;
GetBitContext bits;
init_get_bits(&bits, buf, AC3_HEADER_SIZE * 8);
@ -660,16 +666,16 @@ static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
if(get_bits(&bits, 16) != 0x0b77)
return 0;
bsid = show_bits_long(&bits, 29) & 0x1f;
if(bsid <= 8) { /* Normal AC-3 */
skip_bits(&bits, 16); /* crc */
fscod = get_bits(&bits, 2);
frmsizecod = get_bits(&bits, 6);
if(!ac3_sample_rates[fscod])
if(fscod == 3)
return 0;
bsid = get_bits(&bits, 5);
if(bsid > 8)
return 0;
skip_bits(&bits, 5); /* bsid */
skip_bits(&bits, 3); /* bsmod */
acmod = get_bits(&bits, 3);
if(acmod & 1 && acmod != 1)
@ -686,6 +692,41 @@ static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
*samples = 6 * 256;
return ac3_frame_sizes[frmsizecod][fscod] * 2;
} else if (bsid >= 10 && bsid <= 16) { /* Enhanced AC-3 */
strmtyp = get_bits(&bits, 2);
substreamid = get_bits(&bits, 3);
if (strmtyp != 0 || substreamid != 0)
return 0; /* Currently don't support additional streams */
frmsiz = get_bits(&bits, 11) + 1;
fscod = get_bits(&bits, 2);
if (fscod == 3) {
fscod2 = get_bits(&bits, 2);
numblkscod = 3;
if(fscod2 == 3)
return 0;
*sample_rate = ac3_sample_rates[fscod2] / 2;
} else {
numblkscod = get_bits(&bits, 2);
*sample_rate = ac3_sample_rates[fscod];
}
acmod = get_bits(&bits, 3);
lfeon = get_bits1(&bits);
*samples = eac3_blocks[numblkscod] * 256;
*bit_rate = frmsiz * (*sample_rate) * 16 / (*samples);
*channels = ac3_channels[acmod] + lfeon;
return frmsiz * 2;
}
/* Unsupported bitstream version */
return 0;
}
#endif /* CONFIG_AC3_PARSER */