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#include "mpeg3audio.h"
#include "tables.h"
#include "../libmpeg3.h"
#include "../mpeg3protos.h"
#include <stdio.h>
/* Return 1 if the head check doesn't find a header. */
int mpeg3audio_head_check(unsigned long head)
{
if((head & 0xffe00000) != 0xffe00000) return 1;
if(!((head >> 17) & 3)) return 1;
if(((head >> 12) & 0xf) == 0xf) return 1;
if(!((head >> 12) & 0xf)) return 1;
if(((head >> 10) & 0x3) == 0x3 ) return 1;
if(((head >> 19) & 1) == 1 && ((head >> 17) & 3) == 3 && ((head >> 16) & 1) == 1)
return 1;
if((head & 0xffff0000) == 0xfffe0000) return 1;
return 0;
}
int mpeg3audio_decode_header(mpeg3audio_t *audio)
{
if(audio->newhead & (1 << 20))
{
audio->lsf = (audio->newhead & (1 << 19)) ? 0x0 : 0x1;
audio->mpeg35 = 0;
}
else
{
audio->lsf = 1;
audio->mpeg35 = 1;
}
audio->layer = 4 - ((audio->newhead >> 17) & 3);
if(audio->mpeg35)
audio->sampling_frequency_code = 6 + ((audio->newhead >> 10) & 0x3);
else
audio->sampling_frequency_code = ((audio->newhead >> 10) & 0x3) + (audio->lsf * 3);
audio->error_protection = ((audio->newhead >> 16) & 0x1) ^ 0x1;
audio->bitrate_index = ((audio->newhead >> 12) & 0xf);
audio->padding = ((audio->newhead >> 9) & 0x1);
audio->extension = ((audio->newhead >> 8) & 0x1);
audio->mode = ((audio->newhead >> 6) & 0x3);
audio->mode_ext = ((audio->newhead >> 4) & 0x3);
audio->copyright = ((audio->newhead >> 3) & 0x1);
audio->original = ((audio->newhead >> 2) & 0x1);
audio->emphasis = audio->newhead & 0x3;
audio->channels = (audio->mode == MPG_MD_MONO) ? 1 : 2;
if(audio->channels > 1)
audio->single = -1;
else
audio->single = 3;
audio->prev_framesize = audio->framesize;
if(!audio->bitrate_index) return 1;
audio->bitrate = 1000 * mpeg3_tabsel_123[audio->lsf][audio->layer - 1][audio->bitrate_index];
switch(audio->layer)
{
case 1:
audio->framesize = (long)mpeg3_tabsel_123[audio->lsf][0][audio->bitrate_index] * 12000;
audio->framesize /= mpeg3_freqs[audio->sampling_frequency_code];
audio->framesize = ((audio->framesize + audio->padding) << 2) - 4;
break;
case 2:
audio->framesize = (long)mpeg3_tabsel_123[audio->lsf][1][audio->bitrate_index] * 144000;
audio->framesize /= mpeg3_freqs[audio->sampling_frequency_code];
audio->framesize += audio->padding - 4;
break;
case 3:
if(audio->lsf)
audio->ssize = (audio->channels == 1) ? 9 : 17;
else
audio->ssize = (audio->channels == 1) ? 17 : 32;
if(audio->error_protection)
audio->ssize += 2;
audio->framesize = (long)mpeg3_tabsel_123[audio->lsf][2][audio->bitrate_index] * 144000;
audio->framesize /= mpeg3_freqs[audio->sampling_frequency_code] << (audio->lsf);
audio->framesize = audio->framesize + audio->padding - 4;
break;
default:
return 1;
}
if(audio->framesize > MAXFRAMESIZE) return 1;
return 0;
}
int mpeg3audio_read_frame_body(mpeg3audio_t *audio)
{
int i;
for(i = 0; i < audio->framesize; i++)
{
audio->bsbuf[i] = mpeg3bits_getbits(audio->astream, 8);
}
return 0;
}
/* Seek to the start of the previous header */
int mpeg3audio_prev_header(mpeg3audio_t *audio)
{
int result = 0, i, len = (int)audio->avg_framesize;
for(i = 0; i < len && !result; i++)
{
mpeg3bits_getbits_reverse(audio->astream, 8);
}
/* Get reading in the forward direction again. */
result |= mpeg3bits_refill(audio->astream);
return result;
}
/* Read the next header */
int mpeg3audio_read_header(mpeg3audio_t *audio)
{
unsigned int code;
int i;
int attempt = 0;
int result = 0;
switch(audio->format)
{
case AUDIO_AC3:
result = mpeg3audio_read_ac3_header(audio);
break;
case AUDIO_MPEG:
/* Layer 1 not supported */
if(audio->layer == 1)
{
fprintf(stderr, "mpeg3audio_new: layer 1 not supported\n");
result = 1;
}
audio->newhead = mpeg3bits_showbits(audio->astream, 32);
if(!mpeg3bits_eof(audio->astream) &&
(mpeg3audio_head_check(audio->newhead) || mpeg3audio_decode_header(audio)))
{
do
{
attempt++;
mpeg3bits_getbyte_noptr(audio->astream);
audio->newhead = mpeg3bits_showbits(audio->astream, 32);
}while(!mpeg3bits_eof(audio->astream) &&
attempt < 65536 &&
(mpeg3audio_head_check(audio->newhead) || mpeg3audio_decode_header(audio)));
}
/* Skip the 4 bytes containing the header */
mpeg3bits_getbits(audio->astream, 32);
break;
case AUDIO_PCM:
mpeg3audio_read_pcm_header(audio);
break;
}
return mpeg3bits_eof(audio->astream);
}
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