apps/metadata/a52.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2005 Dave Chapman
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21
  22 #include "metadata.h"
  23 #include "logf.h"
  24
  25 #include "metadata_parsers.h"
  26
  27 static const unsigned short a52_bitrates[] =
  28 {
  29      32,  40,  48,  56,  64,  80,  96, 112, 128, 160,
  30     192, 224, 256, 320, 384, 448, 512, 576, 640
  31 };
  32
  33 /* Only store frame sizes for 44.1KHz - others are simply multiples
  34    of the bitrate */
  35 static const unsigned short a52_441framesizes[] =
  36 {
  37       69 * 2,   70 * 2,   87 * 2,   88 * 2,  104 * 2,  105 * 2,  121 * 2,
  38      122 * 2,  139 * 2,  140 * 2,  174 * 2,  175 * 2,  208 * 2,  209 * 2,
  39      243 * 2,  244 * 2,  278 * 2,  279 * 2,  348 * 2,  349 * 2,  417 * 2,
  40      418 * 2,  487 * 2,  488 * 2,  557 * 2,  558 * 2,  696 * 2,  697 * 2,
  41      835 * 2,  836 * 2,  975 * 2,  976 * 2, 1114 * 2, 1115 * 2, 1253 * 2,
  42     1254 * 2, 1393 * 2, 1394 * 2
  43 };
  44
  45 bool get_a52_metadata(int fd, struct mp3entry *id3)
  46 {
  47     /* Use the trackname part of the id3 structure as a temporary buffer */
  48     unsigned char* buf = (unsigned char *)id3->path;
  49     unsigned long totalsamples;
  50     int i;
  51
  52     if ((lseek(fd, 0, SEEK_SET) < 0) || (read(fd, buf, 5) < 5))
  53     {
  54         return false;
  55     }
  56
  57     if ((buf[0] != 0x0b) || (buf[1] != 0x77))
  58     {
  59         logf("not an A52/AC3 file\n");
  60         return false;
  61     }
  62
  63     i = buf[4] & 0x3e;
  64
  65     if (i > 36)
  66     {
  67         logf("A52: Invalid frmsizecod: %d\n",i);
  68         return false;
  69     }
  70
  71     id3->bitrate = a52_bitrates[i >> 1];
  72     id3->vbr = false;
  73     id3->filesize = filesize(fd);
  74
  75     switch (buf[4] & 0xc0)
  76     {
  77     case 0x00:
  78         id3->frequency = 48000;
  79         id3->bytesperframe=id3->bitrate * 2 * 2;
  80         break;
  81
  82     case 0x40:
  83         id3->frequency = 44100;
  84         id3->bytesperframe = a52_441framesizes[i];
  85         break;
  86
  87     case 0x80:
  88         id3->frequency = 32000;
  89         id3->bytesperframe = id3->bitrate * 3 * 2;
  90         break;
  91
  92     default:
  93         logf("A52: Invalid samplerate code: 0x%02x\n", buf[4] & 0xc0);
  94         return false;
  95         break;
  96     }
  97
  98     /* One A52 frame contains 6 blocks, each containing 256 samples */
  99     totalsamples = id3->filesize / id3->bytesperframe * 6 * 256;
 100     id3->length = totalsamples / id3->frequency * 1000;
 101     return true;
 102 }