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#include <stdio.h>
#include "config.h"
#include "../mp_msg.h"
//----------------------- mp3 audio frame header parser -----------------------
static int tabsel_123[2][3][16] = {
{ {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,},
{0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,},
{0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,} },
{ {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,} }
};
static long freqs[9] = { 44100, 48000, 32000, 22050, 24000, 16000 , 11025 , 12000 , 8000 };
/*
* return frame size or -1 (bad frame)
*/
int mp_decode_mp3_header(unsigned char* hbuf){
int stereo,ssize,crc,lsf,mpeg25,framesize,padding,bitrate_index,sampling_frequency;
unsigned long newhead =
hbuf[0] << 24 |
hbuf[1] << 16 |
hbuf[2] << 8 |
hbuf[3];
// printf("head=0x%08X\n",newhead);
#if 1
// head_check:
if( (newhead & 0xffe00000) != 0xffe00000 ||
(newhead & 0x0000fc00) == 0x0000fc00){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"head_check failed\n");
return -1;
}
#endif
if((4-((newhead>>17)&3))!=3){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"not layer-3\n");
return -1;
}
if( newhead & ((long)1<<20) ) {
lsf = (newhead & ((long)1<<19)) ? 0x0 : 0x1;
mpeg25 = 0;
} else {
lsf = 1;
mpeg25 = 1;
}
if(mpeg25)
sampling_frequency = 6 + ((newhead>>10)&0x3);
else
sampling_frequency = ((newhead>>10)&0x3) + (lsf*3);
if(sampling_frequency>8){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid sampling_frequency\n");
return -1; // valid: 0..8
}
crc = ((newhead>>16)&0x1)^0x1;
bitrate_index = ((newhead>>12)&0xf);
padding = ((newhead>>9)&0x1);
// fr->extension = ((newhead>>8)&0x1);
// fr->mode = ((newhead>>6)&0x3);
// fr->mode_ext = ((newhead>>4)&0x3);
// fr->copyright = ((newhead>>3)&0x1);
// fr->original = ((newhead>>2)&0x1);
// fr->emphasis = newhead & 0x3;
stereo = ( (((newhead>>6)&0x3)) == 3) ? 1 : 2;
if(!bitrate_index){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"Free format not supported.\n");
return -1;
}
if(lsf)
ssize = (stereo == 1) ? 9 : 17;
else
ssize = (stereo == 1) ? 17 : 32;
if(crc) ssize += 2;
framesize = (long) tabsel_123[lsf][2][bitrate_index] * 144000;
framesize /= freqs[sampling_frequency]<<lsf;
framesize += padding;
// if(framesize<=0 || framesize>MAXFRAMESIZE) return FALSE;
return framesize;
}
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