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