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#include <stdio.h>
#include "config.h"
#include "mp3_hdr.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},
{0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,0},
{0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,0} },
{ {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,0},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0} }
};
static long freqs[9] = { 44100, 48000, 32000, // MPEG 1.0
22050, 24000, 16000, // MPEG 2.0
11025, 12000, 8000}; // MPEG 2.5
static int mp_mp3_get_lsf(unsigned char* hbuf){
unsigned long newhead =
hbuf[0] << 24 |
hbuf[1] << 16 |
hbuf[2] << 8 |
hbuf[3];
if( newhead & ((long)1<<20) ) {
return (newhead & ((long)1<<19)) ? 0x0 : 0x1;
}
return 1;
}
/*
* return frame size or -1 (bad frame)
*/
int mp_get_mp3_header(unsigned char* hbuf,int* chans, int* srate, int* spf, int* mpa_layer, int* br){
int stereo,ssize,lsf,framesize,padding,bitrate_index,sampling_frequency, divisor;
int bitrate;
int layer, mult[3] = { 12000, 144000, 144000 };
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 ){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"head_check failed\n");
return -1;
}
#endif
layer = 4-((newhead>>17)&3);
if(layer==4){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"not layer-1/2/3\n");
return -1;
}
sampling_frequency = ((newhead>>10)&0x3); // valid: 0..2
if(sampling_frequency==3){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid sampling_frequency\n");
return -1;
}
if( newhead & ((long)1<<20) ) {
// MPEG 1.0 (lsf==0) or MPEG 2.0 (lsf==1)
lsf = (newhead & ((long)1<<19)) ? 0x0 : 0x1;
sampling_frequency += (lsf*3);
} else {
// MPEG 2.5
lsf = 1;
sampling_frequency += 6;
}
// crc = ((newhead>>16)&0x1)^0x1;
bitrate_index = ((newhead>>12)&0xf); // valid: 1..14
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;
// !checked later through tabsel_123[]!
// if(!bitrate_index || bitrate_index==15){
// 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(!((newhead>>16)&0x1)) ssize += 2; // CRC
bitrate = tabsel_123[lsf][layer-1][bitrate_index];
framesize = bitrate * mult[layer-1];
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"FRAMESIZE: %d, layer: %d, bitrate: %d, mult: %d\n",
framesize, layer, tabsel_123[lsf][layer-1][bitrate_index], mult[layer-1]);
if(!framesize){
mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid framesize/bitrate_index\n");
return -1;
}
divisor = (layer == 3 ? (freqs[sampling_frequency] << lsf) : freqs[sampling_frequency]);
framesize /= divisor;
if(layer==1)
framesize = (framesize+padding)*4;
else
framesize += padding;
// if(framesize<=0 || framesize>MAXFRAMESIZE) return FALSE;
if(srate) {
*srate = freqs[sampling_frequency];
if(spf) {
if(layer == 1)
*spf = 384;
else if(layer == 2)
*spf = 1152;
else if(*srate < 32000)
*spf = 576;
else
*spf = 1152;
}
}
if(mpa_layer) *mpa_layer = layer;
if(chans) *chans = stereo;
if(br) *br = bitrate;
return framesize;
}
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