libmpdemux/mp3_hdr.c

   1 /*
   2  * This file is part of MPlayer.
   3  *
   4  * MPlayer is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * MPlayer is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #include <stdio.h>
  20
  21 #include "config.h"
  22 #include "mp3_hdr.h"
  23 #include "mp_msg.h"
  24
  25 //----------------------- mp3 audio frame header parser -----------------------
  26
  27 static int tabsel_123[2][3][16] = {
  28    { {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,0},
  29      {0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,0},
  30      {0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,0} },
  31
  32    { {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,0},
  33      {0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0},
  34      {0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0} }
  35 };
  36
  37 static long freqs[9] = { 44100, 48000, 32000,   // MPEG 1.0
  38                          22050, 24000, 16000,   // MPEG 2.0
  39                          11025, 12000,  8000};  // MPEG 2.5
  40
  41 /*
  42  * return frame size or -1 (bad frame)
  43  */
  44 int mp_get_mp3_header(unsigned char* hbuf,int* chans, int* srate, int* spf, int* mpa_layer, int* br){
  45     int stereo,ssize,lsf,framesize,padding,bitrate_index,sampling_frequency, divisor;
  46     int bitrate;
  47     int layer, mult[3] = { 12000, 144000, 144000 };
  48     unsigned long newhead =
  49       hbuf[0] << 24 |
  50       hbuf[1] << 16 |
  51       hbuf[2] <<  8 |
  52       hbuf[3];
  53
  54 //    printf("head=0x%08X\n",newhead);
  55
  56     // head_check:
  57     if( (newhead & 0xffe00000) != 0xffe00000 ){
  58         mp_msg(MSGT_DEMUXER,MSGL_DBG2,"head_check failed\n");
  59         return -1;
  60     }
  61
  62     layer = 4-((newhead>>17)&3);
  63     if(layer==4){
  64       mp_msg(MSGT_DEMUXER,MSGL_DBG2,"not layer-1/2/3\n");
  65       return -1;
  66     }
  67
  68     sampling_frequency = ((newhead>>10)&0x3);  // valid: 0..2
  69     if(sampling_frequency==3){
  70         mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid sampling_frequency\n");
  71         return -1;
  72     }
  73
  74     if( newhead & ((long)1<<20) ) {
  75       // MPEG 1.0 (lsf==0) or MPEG 2.0 (lsf==1)
  76       lsf = (newhead & ((long)1<<19)) ? 0x0 : 0x1;
  77       sampling_frequency += (lsf*3);
  78     } else {
  79       // MPEG 2.5
  80       lsf = 1;
  81       sampling_frequency += 6;
  82     }
  83
  84 //    crc = ((newhead>>16)&0x1)^0x1;
  85     bitrate_index = ((newhead>>12)&0xf);  // valid: 1..14
  86     padding   = ((newhead>>9)&0x1);
  87 //    fr->extension = ((newhead>>8)&0x1);
  88 //    fr->mode      = ((newhead>>6)&0x3);
  89 //    fr->mode_ext  = ((newhead>>4)&0x3);
  90 //    fr->copyright = ((newhead>>3)&0x1);
  91 //    fr->original  = ((newhead>>2)&0x1);
  92 //    fr->emphasis  = newhead & 0x3;
  93
  94     stereo    = ( (((newhead>>6)&0x3)) == 3) ? 1 : 2;
  95
  96 // !checked later through tabsel_123[]!
  97 //    if(!bitrate_index || bitrate_index==15){
  98 //      mp_msg(MSGT_DEMUXER,MSGL_DBG2,"Free format not supported.\n");
  99 //      return -1;
 100 //    }
 101
 102     if(lsf)
 103       ssize = (stereo == 1) ? 9 : 17;
 104     else
 105       ssize = (stereo == 1) ? 17 : 32;
 106     if(!((newhead>>16)&0x1)) ssize += 2; // CRC
 107
 108     bitrate = tabsel_123[lsf][layer-1][bitrate_index];
 109     framesize = bitrate * mult[layer-1];
 110
 111     mp_msg(MSGT_DEMUXER,MSGL_DBG2,"FRAMESIZE: %d, layer: %d, bitrate: %d, mult: %d\n",
 112         framesize, layer, tabsel_123[lsf][layer-1][bitrate_index], mult[layer-1]);
 113     if(!framesize){
 114         mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid framesize/bitrate_index\n");
 115         return -1;
 116     }
 117
 118     divisor = (layer == 3 ? (freqs[sampling_frequency] << lsf) : freqs[sampling_frequency]);
 119     framesize /= divisor;
 120     if(layer==1)
 121       framesize = (framesize+padding)*4;
 122     else
 123       framesize += padding;
 124
 125 //    if(framesize<=0 || framesize>MAXFRAMESIZE) return FALSE;
 126     if(srate) {
 127       *srate = freqs[sampling_frequency];
 128       if(spf) {
 129         if(layer == 1)
 130           *spf = 384;
 131         else if(layer == 2)
 132           *spf = 1152;
 133         else if(*srate < 32000)
 134           *spf = 576;
 135         else
 136           *spf = 1152;
 137       }
 138     }
 139     if(mpa_layer) *mpa_layer = layer;
 140     if(chans) *chans = stereo;
 141     if(br) *br = bitrate;
 142
 143     return framesize;
 144 }