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 "mp_msg.h"
  23
  24 //----------------------- mp3 audio frame header parser -----------------------
  25
  26 static int tabsel_123[2][3][16] = {
  27    { {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,0},
  28      {0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,0},
  29      {0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,0} },
  30
  31    { {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,0},
  32      {0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0},
  33      {0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0} }
  34 };
  35
  36 static long freqs[9] = { 44100, 48000, 32000,   // MPEG 1.0
  37                          22050, 24000, 16000,   // MPEG 2.0
  38                          11025, 12000,  8000};  // MPEG 2.5
  39
  40 int mp_mp3_get_lsf(unsigned char* hbuf){
  41     unsigned long newhead =
  42       hbuf[0] << 24 |
  43       hbuf[1] << 16 |
  44       hbuf[2] <<  8 |
  45       hbuf[3];
  46     if( newhead & ((long)1<<20) ) {
  47       return (newhead & ((long)1<<19)) ? 0x0 : 0x1;
  48     }
  49     return 1;
  50 }
  51
  52 /*
  53  * return frame size or -1 (bad frame)
  54  */
  55 int mp_get_mp3_header(unsigned char* hbuf,int* chans, int* srate, int* spf, int* mpa_layer, int* br){
  56     int stereo,ssize,lsf,framesize,padding,bitrate_index,sampling_frequency, divisor;
  57     int bitrate;
  58     int layer, mult[3] = { 12000, 144000, 144000 };
  59     unsigned long newhead =
  60       hbuf[0] << 24 |
  61       hbuf[1] << 16 |
  62       hbuf[2] <<  8 |
  63       hbuf[3];
  64
  65 //    printf("head=0x%08X\n",newhead);
  66
  67 #if 1
  68     // head_check:
  69     if( (newhead & 0xffe00000) != 0xffe00000 ){
  70         mp_msg(MSGT_DEMUXER,MSGL_DBG2,"head_check failed\n");
  71         return -1;
  72     }
  73 #endif
  74
  75     layer = 4-((newhead>>17)&3);
  76     if(layer==4){
  77       mp_msg(MSGT_DEMUXER,MSGL_DBG2,"not layer-1/2/3\n");
  78       return -1;
  79     }
  80
  81     sampling_frequency = ((newhead>>10)&0x3);  // valid: 0..2
  82     if(sampling_frequency==3){
  83         mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid sampling_frequency\n");
  84         return -1;
  85     }
  86
  87     if( newhead & ((long)1<<20) ) {
  88       // MPEG 1.0 (lsf==0) or MPEG 2.0 (lsf==1)
  89       lsf = (newhead & ((long)1<<19)) ? 0x0 : 0x1;
  90       sampling_frequency += (lsf*3);
  91     } else {
  92       // MPEG 2.5
  93       lsf = 1;
  94       sampling_frequency += 6;
  95     }
  96
  97 //    crc = ((newhead>>16)&0x1)^0x1;
  98     bitrate_index = ((newhead>>12)&0xf);  // valid: 1..14
  99     padding   = ((newhead>>9)&0x1);
 100 //    fr->extension = ((newhead>>8)&0x1);
 101 //    fr->mode      = ((newhead>>6)&0x3);
 102 //    fr->mode_ext  = ((newhead>>4)&0x3);
 103 //    fr->copyright = ((newhead>>3)&0x1);
 104 //    fr->original  = ((newhead>>2)&0x1);
 105 //    fr->emphasis  = newhead & 0x3;
 106
 107     stereo    = ( (((newhead>>6)&0x3)) == 3) ? 1 : 2;
 108
 109 // !checked later through tabsel_123[]!
 110 //    if(!bitrate_index || bitrate_index==15){
 111 //      mp_msg(MSGT_DEMUXER,MSGL_DBG2,"Free format not supported.\n");
 112 //      return -1;
 113 //    }
 114
 115     if(lsf)
 116       ssize = (stereo == 1) ? 9 : 17;
 117     else
 118       ssize = (stereo == 1) ? 17 : 32;
 119     if(!((newhead>>16)&0x1)) ssize += 2; // CRC
 120
 121     bitrate = tabsel_123[lsf][layer-1][bitrate_index];
 122     framesize = bitrate * mult[layer-1];
 123
 124     mp_msg(MSGT_DEMUXER,MSGL_DBG2,"FRAMESIZE: %d, layer: %d, bitrate: %d, mult: %d\n",
 125         framesize, layer, tabsel_123[lsf][layer-1][bitrate_index], mult[layer-1]);
 126     if(!framesize){
 127         mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid framesize/bitrate_index\n");
 128         return -1;
 129     }
 130
 131     divisor = (layer == 3 ? (freqs[sampling_frequency] << lsf) : freqs[sampling_frequency]);
 132     framesize /= divisor;
 133     if(layer==1)
 134       framesize = (framesize+padding)*4;
 135     else
 136       framesize += padding;
 137
 138 //    if(framesize<=0 || framesize>MAXFRAMESIZE) return FALSE;
 139     if(srate) {
 140       *srate = freqs[sampling_frequency];
 141       if(spf) {
 142         if(layer == 1)
 143           *spf = 384;
 144         else if(layer == 2)
 145           *spf = 1152;
 146         else if(*srate < 32000)
 147           *spf = 576;
 148         else
 149           *spf = 1152;
 150       }
 151     }
 152     if(mpa_layer) *mpa_layer = layer;
 153     if(chans) *chans = stereo;
 154     if(br) *br = bitrate;
 155
 156     return framesize;
 157 }
 158