apps/metadata/mp3.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Daniel Stenberg
  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  * Parts of this code has been stolen from the Ample project and was written
  23  * by David H�deman. It has since been extended and enhanced pretty much by
  24  * all sorts of friendly Rockbox people.
  25  *
  26  */
  27
  28  /* tagResolver and associated code copyright 2003 Thomas Paul Diffenbach
  29  */
  30
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include <stdbool.h>
  35 #include "string-extra.h"
  36 #include "config.h"
  37 #include "file.h"
  38 #include "logf.h"
  39
  40 #include "system.h"
  41 #include "metadata.h"
  42 #include "mp3data.h"
  43 #include "metadata_common.h"
  44 #include "metadata_parsers.h"
  45
  46 /*
  47  * Calculates the length (in milliseconds) of an MP3 file.
  48  *
  49  * Modified to only use integers.
  50  *
  51  * Arguments: file - the file to calculate the length upon
  52  *            entry - the entry to update with the length
  53  *
  54  * Returns: the song length in milliseconds,
  55  *          0 means that it couldn't be calculated
  56  */
  57 static int getsonglength(int fd, struct mp3entry *entry)
  58 {
  59     unsigned long filetime = 0;
  60     struct mp3info info;
  61     long bytecount;
  62
  63     /* Start searching after ID3v2 header */
  64     if(-1 == lseek(fd, entry->id3v2len, SEEK_SET))
  65         return 0;
  66
  67     bytecount = get_mp3file_info(fd, &info);
  68
  69     logf("Space between ID3V2 tag and first audio frame: 0x%lx bytes",
  70            bytecount);
  71
  72     if(bytecount < 0)
  73         return -1;
  74
  75     bytecount += entry->id3v2len;
  76
  77     /* Validate byte count, in case the file has been edited without
  78      * updating the header.
  79      */
  80     if (info.byte_count)
  81     {
  82         const unsigned long expected = entry->filesize - entry->id3v1len
  83             - entry->id3v2len;
  84         const unsigned long diff = MAX(10240, info.byte_count / 20);
  85
  86         if ((info.byte_count > expected + diff)
  87             || (info.byte_count < expected - diff))
  88         {
  89             logf("Note: info.byte_count differs from expected value by "
  90                  "%ld bytes", labs((long) (expected - info.byte_count)));
  91             info.byte_count = 0;
  92             info.frame_count = 0;
  93             info.file_time = 0;
  94             info.enc_padding = 0;
  95
  96             /* Even if the bitrate was based on "known bad" values, it
  97              * should still be better for VBR files than using the bitrate
  98              * of the first audio frame.
  99              */
 100         }
 101     }
 102
 103     entry->bitrate = info.bitrate;
 104     entry->frequency = info.frequency;
 105     entry->version = info.version;
 106     entry->layer = info.layer;
 107     switch(entry->layer) {
 108 #if CONFIG_CODEC==SWCODEC
 109         case 0:
 110             entry->codectype=AFMT_MPA_L1;
 111             break;
 112 #endif
 113         case 1:
 114             entry->codectype=AFMT_MPA_L2;
 115             break;
 116         case 2:
 117             entry->codectype=AFMT_MPA_L3;
 118             break;
 119     }
 120
 121     /* If the file time hasn't been established, this may be a fixed
 122        rate MP3, so just use the default formula */
 123
 124     filetime = info.file_time;
 125
 126     if(filetime == 0)
 127     {
 128         /* Prevent a division by zero */
 129         if (info.bitrate < 8)
 130             filetime = 0;
 131         else
 132             filetime = (entry->filesize - bytecount) / (info.bitrate / 8);
 133         /* bitrate is in kbps so this delivers milliseconds. Doing bitrate / 8
 134          * instead of filesize * 8 is exact, because mpeg audio bitrates are
 135          * always multiples of 8, and it avoids overflows. */
 136     }
 137
 138     entry->frame_count = info.frame_count;
 139
 140     entry->vbr = info.is_vbr;
 141     entry->has_toc = info.has_toc;
 142
 143 #if CONFIG_CODEC==SWCODEC
 144     if (!entry->lead_trim)
 145         entry->lead_trim = info.enc_delay;
 146     if (!entry->tail_trim)
 147         entry->tail_trim = info.enc_padding;
 148 #endif
 149
 150     memcpy(entry->toc, info.toc, sizeof(info.toc));
 151
 152     entry->vbr_header_pos = info.vbr_header_pos;
 153
 154     /* Update the seek point for the first playable frame */
 155     entry->first_frame_offset = bytecount;
 156     logf("First frame is at %lx", entry->first_frame_offset);
 157
 158     return filetime;
 159 }
 160
 161 /*
 162  * Checks all relevant information (such as ID3v1 tag, ID3v2 tag, length etc)
 163  * about an MP3 file and updates it's entry accordingly.
 164  *
 165   Note, that this returns true for successful, false for error! */
 166 bool get_mp3_metadata(int fd, struct mp3entry *entry)
 167 {
 168     entry->title = NULL;
 169     entry->filesize = filesize(fd);
 170     entry->id3v2len = getid3v2len(fd);
 171     entry->tracknum = 0;
 172     entry->discnum = 0;
 173
 174     if (entry->id3v2len)
 175         setid3v2title(fd, entry);
 176     int len = getsonglength(fd, entry);
 177     if (len < 0)
 178         return false;
 179     entry->length = len;
 180
 181     /* Subtract the meta information from the file size to get
 182        the true size of the MP3 stream */
 183     entry->filesize -= entry->first_frame_offset;
 184
 185     /* only seek to end of file if no id3v2 tags were found */
 186     if (!entry->id3v2len) {
 187         setid3v1title(fd, entry);
 188     }
 189
 190     if(!entry->length || (entry->filesize < 8 ))
 191         /* no song length or less than 8 bytes is hereby considered to be an
 192            invalid mp3 and won't be played by us! */
 193         return false;
 194
 195     return true;
 196 }