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Code Issues Releases Activity

move E-AC3 header parsing to ff_ac3_parse_header()

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Originally committed as revision 11420 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-01-05 18:39:55 +00:00
parent 86ad4c7e1b
commit 646800f79c
2 changed files with 40 additions and 47 deletions
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84
libavcodec/ac3_parser.c
View File

@ -38,6 +38,7 @@ int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
{
GetBitContext gbc;
int frame_size_code;
int num_blocks;
memset(hdr, 0, sizeof(*hdr));
@ -47,11 +48,13 @@ int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
if(hdr->sync_word != 0x0B77)
return AC3_PARSE_ERROR_SYNC;
/* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
/* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
hdr->bitstream_id = show_bits_long(&gbc, 29) & 0x1F;
if(hdr->bitstream_id > 10)
if(hdr->bitstream_id > 16)
return AC3_PARSE_ERROR_BSID;
if(hdr->bitstream_id <= 10) {
/* Normal AC-3 */
hdr->crc1 = get_bits(&gbc, 16);
hdr->sr_code = get_bits(&gbc, 2);
if(hdr->sr_code == 3)
@ -81,6 +84,37 @@ int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
} else {
/* Enhanced AC-3 */
hdr->crc1 = 0;
skip_bits(&gbc, 2); // skip stream type
skip_bits(&gbc, 3); // skip substream id
hdr->frame_size = (get_bits(&gbc, 11) + 1) << 1;
if(hdr->frame_size < AC3_HEADER_SIZE)
return AC3_PARSE_ERROR_FRAME_SIZE;
hdr->sr_code = get_bits(&gbc, 2);
if (hdr->sr_code == 3) {
int sr_code2 = get_bits(&gbc, 2);
if(sr_code2 == 3)
return AC3_PARSE_ERROR_SAMPLE_RATE;
hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
hdr->sr_shift = 1;
num_blocks = 6;
} else {
num_blocks = eac3_blocks[get_bits(&gbc, 2)];
hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
hdr->sr_shift = 0;
}
hdr->channel_mode = get_bits(&gbc, 3);
hdr->lfe_on = get_bits1(&gbc);
hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
(num_blocks * 256.0));
hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
}
return 0;
}
@ -89,62 +123,18 @@ static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
int *bit_rate, int *samples)
{
int err;
unsigned int sr_code, channel_mode, bitstream_id, lfe_on;
unsigned int stream_type, substream_id, frame_size, sr_code2, num_blocks_code;
GetBitContext bits;
AC3HeaderInfo hdr;
err = ff_ac3_parse_header(buf, &hdr);
if(err < 0 && err != -2)
if(err < 0)
return 0;
bitstream_id = hdr.bitstream_id;
if(bitstream_id <= 10) { /* Normal AC-3 */
*sample_rate = hdr.sample_rate;
*bit_rate = hdr.bit_rate;
*channels = hdr.channels;
*samples = AC3_FRAME_SIZE;
return hdr.frame_size;
} else if (bitstream_id > 10 && bitstream_id <= 16) { /* Enhanced AC-3 */
init_get_bits(&bits, &buf[2], (AC3_HEADER_SIZE-2) * 8);
stream_type = get_bits(&bits, 2);
substream_id = get_bits(&bits, 3);
if (stream_type != 0 || substream_id != 0)
return 0; /* Currently don't support additional streams */
frame_size = get_bits(&bits, 11) + 1;
if(frame_size*2 < AC3_HEADER_SIZE)
return 0;
sr_code = get_bits(&bits, 2);
if (sr_code == 3) {
sr_code2 = get_bits(&bits, 2);
num_blocks_code = 3;
if(sr_code2 == 3)
return 0;
*sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
} else {
num_blocks_code = get_bits(&bits, 2);
*sample_rate = ff_ac3_sample_rate_tab[sr_code];
}
channel_mode = get_bits(&bits, 3);
lfe_on = get_bits1(&bits);
*samples = eac3_blocks[num_blocks_code] * 256;
*bit_rate = frame_size * (*sample_rate) * 16 / (*samples);
*channels = ff_ac3_channels_tab[channel_mode] + lfe_on;
return frame_size * 2;
}
/* Unsupported bitstream version */
return 0;
}
static int ac3_parse_init(AVCodecParserContext *s1)

3
libavcodec/ac3dec.c
View File

@ -338,6 +338,9 @@ static int ac3_parse_header(AC3DecodeContext *s)
if(err)
return err;
if(hdr.bitstream_id > 10)
return AC3_PARSE_ERROR_BSID;
/* get decoding parameters from header info */
s->bit_alloc_params.sr_code = hdr.sr_code;
s->channel_mode = hdr.channel_mode;