lib/mp3.c

   1 /* mp3.c
   2    Routines for handling .mp3 files
   3
   4    Part of the swftools package.
   5
   6    Copyright (c) 2005 Joel Yliluoma <bisqwit@iki.fi>
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
  21
  22 #include <stdlib.h>
  23 #include <stdio.h>
  24 #include <string.h>
  25
  26 #include "mp3.h"
  27
  28 struct MP3Frame
  29 {
  30     unsigned bitrate;
  31     unsigned samprate;
  32     unsigned chanmode;
  33     unsigned framesize;
  34     unsigned char* data;
  35     struct MP3Frame* next;
  36 };
  37
  38 //                                    0          4           8               C
  39 static const unsigned BR_mpeg1[16] = {0,32,40,48,56,64,80,96,112,128,160,192,224,256,320,0};
  40 static const unsigned BR_mpeg2[16] = {0,8, 16,24,32,40,48,56, 64, 80, 96,112,128,144,160,0};
  41 static const unsigned BR_reserved[16] = {0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0};
  42 static const unsigned*const BR[4] = {BR_mpeg2, BR_reserved, BR_mpeg2, BR_mpeg1};
  43
  44 static const unsigned SR_mpeg1[4] = {44100,48000,32000,0};
  45 static const unsigned SR_mpeg2[4] = {22050,24000,16000,0};
  46 static const unsigned SR_mpeg25[4] = {11025,12000,8000,0};
  47 static const unsigned SR_reserved[4] = {0,0,0,0};
  48 static const unsigned*const SR[4] = {SR_mpeg25, SR_reserved, SR_mpeg2, SR_mpeg1};
  49
  50 int mp3_read(struct MP3*mp3, const char* filename)
  51 {
  52     struct MP3Frame* root = 0;
  53     struct MP3Frame** cur = &root;
  54
  55     unsigned totalsize      = 0;
  56     unsigned first_samprate = 0;
  57     unsigned nframes = 0;
  58     int first_chanmode = -1;
  59
  60     FILE*fi = fopen(filename, "rb");
  61     if(!fi) return 0;
  62
  63     for(;;)
  64     {
  65         unsigned char FrameBuf[2048];
  66         unsigned char* hdr = FrameBuf;
  67         unsigned char* data = FrameBuf+4;
  68         unsigned char* frdata;
  69
  70         unsigned char mpegver;
  71         unsigned padding;
  72         unsigned bitrate;
  73         unsigned samprate;
  74         unsigned framesize;
  75         int chanmode;
  76
  77         if(fread(hdr,1,4,fi) < 4) break;
  78
  79         if(hdr[0] == 'I' && hdr[1] == 'D' && hdr[2] == '3')
  80         {
  81             /* Skip ID3 header */
  82             unsigned id3_size = 0;
  83             if(fread(FrameBuf, 1, 6, fi) < 6) break;
  84
  85             id3_size = (FrameBuf[5])
  86                      + (FrameBuf[4] << 7)
  87                      + (FrameBuf[3] << 14)
  88                      + (FrameBuf[2] << 21);
  89             fprintf(stderr, "readMP3: skipping ID3 tag (10+%u bytes)\n", id3_size);
  90             if(fseek(fi, id3_size, SEEK_CUR) < 0)
  91             {
  92                 /* Cannot seek? Try reading. */
  93                 char* tmpbuf = (char*)malloc(id3_size);
  94                 int nread=0;
  95                 if(!tmpbuf)
  96                 {
  97                     fprintf(stderr, "readMP3: fseek and malloc both failed?\n");
  98                     break;
  99                 }
 100                 nread = fread(tmpbuf, 1, id3_size, fi);
 101                 free(tmpbuf);
 102                 if(nread < id3_size) break;
 103             }
 104             continue;
 105         }
 106
 107
 108         if(hdr[0] != 0xFF
 109         || (hdr[1] & 0xE0) != 0xE0)
 110         {
 111             fprintf(stderr, "readMP3: invalid header %02X %02X %02X %02X\n",
 112                 hdr[0],hdr[1],hdr[2],hdr[3]);
 113             break;
 114         }
 115
 116         mpegver = (hdr[1] >> 3) & 0x03;
 117
 118         bitrate  = BR[mpegver][ (hdr[2] >> 4) & 0x0F ] * 1000;
 119         samprate = SR[mpegver][ (hdr[2] >> 2) & 0x03 ];
 120         chanmode = (hdr[3] >> 6) & 0x03;
 121
 122         padding = (hdr[2] & 2) ? 1 : 0;
 123
 124         if(!bitrate || !samprate)
 125         {
 126             /* Invalid frame */
 127             /*break;*/
 128         }
 129         if(!first_samprate) first_samprate = samprate;
 130         else if(first_samprate != samprate)
 131         {
 132             /* Sampling rate changed?!? */
 133             fprintf(stderr, "readMP3: sampling rate changed?\n");
 134             /*break;*/
 135         }
 136         if(first_chanmode<0) first_chanmode = chanmode;
 137         else if(first_chanmode != chanmode)
 138         {
 139             /* Channel mode changed?!? */
 140             fprintf(stderr, "readMP3: chanmode changed?\n");
 141             /*break;*/
 142         }
 143
 144         framesize = ((mpegver == 3 ? 144 : 72) * bitrate) / samprate + padding;
 145
 146 /*
 147         fprintf(stderr, "%02X %02X %02X %02X - bitrate=%u,samprate=%u,chanmode=%u,padding=%u,framesize=%u\n",
 148             hdr[0],hdr[1],hdr[2],hdr[3],bitrate,samprate,chanmode,padding,framesize);
 149 */
 150         if(framesize > sizeof(FrameBuf)) break;
 151         if(fread(data, 1, framesize - 4, fi) < framesize-4)
 152         {
 153             fprintf(stderr, "readMP3: short read at frame %u\n", nframes);
 154             break;
 155         }
 156
 157         if(!bitrate || !samprate) continue;
 158
 159         frdata = (unsigned char*)malloc(framesize);
 160         if(!frdata)
 161         {
 162             fprintf(stderr, "readMP3: malloc failed\n");
 163             break;
 164         }
 165
 166         *cur = (struct MP3Frame*)malloc(sizeof(*root));
 167         if(!*cur)
 168         {
 169             fprintf(stderr, "readMP3: malloc failed\n");
 170             free(frdata);
 171             break;
 172         }
 173
 174         (*cur)->next = 0;
 175         (*cur)->bitrate = bitrate;
 176         (*cur)->samprate = samprate;
 177         (*cur)->chanmode = chanmode;
 178         (*cur)->framesize = framesize;
 179         (*cur)->data = frdata;
 180
 181         memcpy(frdata, FrameBuf, framesize);
 182         cur = &(*cur)->next;
 183
 184         totalsize += framesize;
 185         ++nframes;
 186     }
 187     if(!root)
 188     {
 189         fprintf(stderr, "readMP3: not a MP3 file\n");
 190         fclose(fi);
 191         return 0;
 192     }
 193
 194     /*
 195     fprintf(stderr, "readMP3: read %u frames (%u bytes)\n", nframes, totalsize);
 196     */
 197
 198     mp3->SampRate = first_samprate;
 199     mp3->Channels = first_chanmode == 3 ? 1 : 2;
 200     mp3->NumFrames = nframes;
 201     mp3->size = totalsize;
 202     mp3->data = (unsigned char*)malloc(mp3->size);
 203     if(mp3->data)
 204     {
 205         unsigned pos=0;
 206         struct MP3Frame* it;
 207         for(it=root; it; it=it->next)
 208         {
 209             memcpy(mp3->data + pos, it->data, it->framesize);
 210             pos += it->framesize;
 211         }
 212     }
 213     else
 214     {
 215         fprintf(stderr, "readMP3: malloc failed\n");
 216     }
 217
 218     while(root)
 219     {
 220         struct MP3Frame* next = root->next;
 221         free(root->data);
 222         free(root);
 223         root = next;
 224     }
 225
 226     fclose(fi);
 227     return mp3->data != NULL;
 228 }
 229
 230 void mp3_clear(struct MP3*mp3)
 231 {
 232     free(mp3->data);
 233     mp3->data = 0;
 234 }
 235
 236