int mpeg3audio_do_pcm(mpeg3audio_t *audio)
{
int i, j, k;
MPEG3_INT16 sample;
int frame_samples = (audio->framesize - 3) / audio->channels / 2;
if(mpeg3bits_read_buffer(audio->astream, audio->ac3_buffer, frame_samples * audio->channels * 2))
return 1;
/* Need more room */
if(audio->pcm_point / audio->channels >= audio->pcm_allocated - MPEG3AUDIO_PADDING * audio->channels)
{
mpeg3audio_replace_buffer(audio, audio->pcm_allocated + MPEG3AUDIO_PADDING * audio->channels);
}
k = 0;
for(i = 0; i < frame_samples; i++)
{
for(j = 0; j < audio->channels; j++)
{
sample = ((MPEG3_INT16)(audio->ac3_buffer[k++])) << 8;
sample |= audio->ac3_buffer[k++];
audio->pcm_sample[audio->pcm_point + i * audio->channels + j] =
(mpeg3_real_t)sample / 32767;
}
}
audio->pcm_point += frame_samples * audio->channels;
return 0;
}
int mpeg3audio_read_ac3_header(mpeg3audio_t *audio)
{
unsigned int code, crc;
unsigned int i;
mpeg3_ac3bsi_t *bsi = &(audio->ac3_bsi);
/* Get the sync code */
code = mpeg3bits_getbits(audio->astream, 16);
while(!mpeg3bits_eof(audio->astream) && code != MPEG3_AC3_START_CODE)
{
code <<= 8;
code &= 0xffff;
code |= mpeg3bits_getbits(audio->astream, 8);
}
if(mpeg3bits_eof(audio->astream)) return 1;
/* Get crc1 - we don't actually use this data though */
/* The crc can be the same as the sync code or come after a sync code repeated twice */
crc = mpeg3bits_getbits(audio->astream, 16);
/* Got the sync code. Read the entire frame into a buffer if possible. */
if(audio->avg_framesize > 0)
{
if(mpeg3bits_read_buffer(audio->astream, audio->ac3_buffer, audio->framesize - 4))
return 1;
mpeg3bits_use_ptr(audio->astream, audio->ac3_buffer);
}
/* Get the sampling rate code */
audio->sampling_frequency_code = mpeg3bits_getbits(audio->astream, 2);
/* Get the frame size code */
audio->ac3_framesize_code = mpeg3bits_getbits(audio->astream, 6);
audio->bitrate = framesize_codes[audio->ac3_framesize_code].bit_rate;
audio->avg_framesize = audio->framesize = 2 * framesize_codes[audio->ac3_framesize_code].frm_size[audio->sampling_frequency_code];
/* Check the AC-3 version number */
bsi->bsid = mpeg3bits_getbits(audio->astream, 5);
/* Get the audio service provided by the steram */
bsi->bsmod = mpeg3bits_getbits(audio->astream, 3);
/* Get the audio coding mode (ie how many channels)*/
bsi->acmod = mpeg3bits_getbits(audio->astream, 3);
/* Predecode the number of full bandwidth channels as we use this
* number a lot */
bsi->nfchans = mpeg3_ac3_acmodes[bsi->acmod];
audio->channels = bsi->nfchans;
/* If it is in use, get the centre channel mix level */
if((bsi->acmod & 0x1) && (bsi->acmod != 0x1))
bsi->cmixlev = mpeg3bits_getbits(audio->astream, 2);
/* If it is in use, get the surround channel mix level */
if(bsi->acmod & 0x4)
bsi->surmixlev = mpeg3bits_getbits(audio->astream, 2);
/* Get the dolby surround mode if in 2/0 mode */
if(bsi->acmod == 0x2)
bsi->dsurmod= mpeg3bits_getbits(audio->astream, 2);
/* Is the low frequency effects channel on? */
bsi->lfeon = mpeg3bits_getbits(audio->astream, 1);
/* Get the dialogue normalization level */
bsi->dialnorm = mpeg3bits_getbits(audio->astream, 5);
/* Does compression gain exist? */
bsi->compre = mpeg3bits_getbits(audio->astream, 1);
if (bsi->compre)
{
/* Get compression gain */
bsi->compr = mpeg3bits_getbits(audio->astream, 8);
}
/* Does language code exist? */
bsi->langcode = mpeg3bits_getbits(audio->astream, 1);
if (bsi->langcode)
{
/* Get langauge code */
bsi->langcod = mpeg3bits_getbits(audio->astream, 8);
}
/* Does audio production info exist? */
bsi->audprodie = mpeg3bits_getbits(audio->astream, 1);
if (bsi->audprodie)
{
/* Get mix level */
bsi->mixlevel = mpeg3bits_getbits(audio->astream, 5);
/* Get room type */
bsi->roomtyp = mpeg3bits_getbits(audio->astream, 2);
}
/* If we're in dual mono mode then get some extra info */
if (bsi->acmod == 0)
{
/* Get the dialogue normalization level two */
bsi->dialnorm2 = mpeg3bits_getbits(audio->astream, 5);
/* Does compression gain two exist? */
bsi->compr2e = mpeg3bits_getbits(audio->astream, 1);
if (bsi->compr2e)
{
/* Get compression gain two */
bsi->compr2 = mpeg3bits_getbits(audio->astream, 8);
}
/* Does language code two exist? */
bsi->langcod2e = mpeg3bits_getbits(audio->astream, 1);
if (bsi->langcod2e)
{
/* Get langauge code two */
bsi->langcod2 = mpeg3bits_getbits(audio->astream, 8);
}
/* Does audio production info two exist? */
bsi->audprodi2e = mpeg3bits_getbits(audio->astream, 1);
if (bsi->audprodi2e)
{
/* Get mix level two */
bsi->mixlevel2 = mpeg3bits_getbits(audio->astream, 5);
/* Get room type two */
bsi->roomtyp2 = mpeg3bits_getbits(audio->astream, 2);
}
}
/* Get the copyright bit */
bsi->copyrightb = mpeg3bits_getbits(audio->astream, 1);
/* Get the original bit */
bsi->origbs = mpeg3bits_getbits(audio->astream, 1);
/* Does timecode one exist? */
bsi->timecod1e = mpeg3bits_getbits(audio->astream, 1);
if(bsi->timecod1e)
bsi->timecod1 = mpeg3bits_getbits(audio->astream, 14);
/* Does timecode two exist? */
bsi->timecod2e = mpeg3bits_getbits(audio->astream, 1);
if(bsi->timecod2e)
bsi->timecod2 = mpeg3bits_getbits(audio->astream, 14);
/* Does addition info exist? */
bsi->addbsie = mpeg3bits_getbits(audio->astream, 1);
if(bsi->addbsie)
{
/* Get how much info is there */
bsi->addbsil = mpeg3bits_getbits(audio->astream, 6);
/* Get the additional info */
for(i = 0; i < (bsi->addbsil + 1); i++)
bsi->addbsi[i] = mpeg3bits_getbits(audio->astream, 8);
}
if(mpeg3bits_eof(audio->astream))
{
mpeg3bits_use_demuxer(audio->astream);
return 1;
}
return 0;
// return mpeg3bits_error(audio->astream);
}
