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 "config.h"
  36 #include "file.h"
  37 #include "logf.h"
  38
  39 #include "system.h"
  40 #include "metadata.h"
  41 #include "mp3data.h"
  42 #include "metadata_common.h"
  43 #include "metadata_parsers.h"
  44
  45 /*
  46  * Calculates the length (in milliseconds) of an MP3 file.
  47  *
  48  * Modified to only use integers.
  49  *
  50  * Arguments: file - the file to calculate the length upon
  51  *            entry - the entry to update with the length
  52  *
  53  * Returns: the song length in milliseconds,
  54  *          0 means that it couldn't be calculated
  55  */
  56 static int getsonglength(int fd, struct mp3entry *entry)
  57 {
  58     unsigned long filetime = 0;
  59     struct mp3info info;
  60     long bytecount;
  61
  62     /* Start searching after ID3v2 header */
  63     if(-1 == lseek(fd, entry->id3v2len, SEEK_SET))
  64         return 0;
  65
  66     bytecount = get_mp3file_info(fd, &info);
  67
  68     logf("Space between ID3V2 tag and first audio frame: 0x%lx bytes",
  69            bytecount);
  70
  71     if(bytecount < 0)
  72         return -1;
  73
  74     bytecount += entry->id3v2len;
  75
  76     /* Validate byte count, in case the file has been edited without
  77      * updating the header.
  78      */
  79     if (info.byte_count)
  80     {
  81         const unsigned long expected = entry->filesize - entry->id3v1len
  82             - entry->id3v2len;
  83         const unsigned long diff = MAX(10240, info.byte_count / 20);
  84
  85         if ((info.byte_count > expected + diff)
  86             || (info.byte_count < expected - diff))
  87         {
  88             logf("Note: info.byte_count differs from expected value by "
  89                  "%ld bytes", labs((long) (expected - info.byte_count)));
  90             info.byte_count = 0;
  91             info.frame_count = 0;
  92             info.file_time = 0;
  93             info.enc_padding = 0;
  94
  95             /* Even if the bitrate was based on "known bad" values, it
  96              * should still be better for VBR files than using the bitrate
  97              * of the first audio frame.
  98              */
  99         }
 100     }
 101
 102     entry->bitrate = info.bitrate;
 103     entry->frequency = info.frequency;
 104     entry->version = info.version;
 105     entry->layer = info.layer;
 106     switch(entry->layer) {
 107 #if CONFIG_CODEC==SWCODEC
 108         case 0:
 109             entry->codectype=AFMT_MPA_L1;
 110             break;
 111 #endif
 112         case 1:
 113             entry->codectype=AFMT_MPA_L2;
 114             break;
 115         case 2:
 116             entry->codectype=AFMT_MPA_L3;
 117             break;
 118     }
 119
 120     /* If the file time hasn't been established, this may be a fixed
 121        rate MP3, so just use the default formula */
 122
 123     filetime = info.file_time;
 124
 125     if(filetime == 0)
 126     {
 127         /* Prevent a division by zero */
 128         if (info.bitrate < 8)
 129             filetime = 0;
 130         else
 131             filetime = (entry->filesize - bytecount) / (info.bitrate / 8);
 132         /* bitrate is in kbps so this delivers milliseconds. Doing bitrate / 8
 133          * instead of filesize * 8 is exact, because mpeg audio bitrates are
 134          * always multiples of 8, and it avoids overflows. */
 135     }
 136
 137     entry->frame_count = info.frame_count;
 138
 139     entry->vbr = info.is_vbr;
 140     entry->has_toc = info.has_toc;
 141
 142 #if CONFIG_CODEC==SWCODEC
 143     if (!entry->lead_trim)
 144         entry->lead_trim = info.enc_delay;
 145     if (!entry->tail_trim)
 146         entry->tail_trim = info.enc_padding;
 147 #endif
 148
 149     memcpy(entry->toc, info.toc, sizeof(info.toc));
 150
 151     entry->vbr_header_pos = info.vbr_header_pos;
 152
 153     /* Update the seek point for the first playable frame */
 154     entry->first_frame_offset = bytecount;
 155     logf("First frame is at %lx", entry->first_frame_offset);
 156
 157     return filetime;
 158 }
 159
 160 /*
 161  * Checks all relevant information (such as ID3v1 tag, ID3v2 tag, length etc)
 162  * about an MP3 file and updates it's entry accordingly.
 163  *
 164   Note, that this returns true for successful, false for error! */
 165 bool get_mp3_metadata(int fd, struct mp3entry *entry, const char *filename)
 166 {
 167 #if CONFIG_CODEC != SWCODEC
 168     memset(entry, 0, sizeof(struct mp3entry));
 169 #endif
 170
 171     strlcpy(entry->path, filename, sizeof(entry->path));
 172
 173     entry->title = NULL;
 174     entry->filesize = filesize(fd);
 175     entry->id3v2len = getid3v2len(fd);
 176     entry->tracknum = 0;
 177     entry->discnum = 0;
 178
 179     if (entry->id3v2len)
 180         setid3v2title(fd, entry);
 181     int len = getsonglength(fd, entry);
 182     if (len < 0)
 183         return false;
 184     entry->length = len;
 185
 186     /* Subtract the meta information from the file size to get
 187        the true size of the MP3 stream */
 188     entry->filesize -= entry->first_frame_offset;
 189
 190     /* only seek to end of file if no id3v2 tags were found */
 191     if (!entry->id3v2len) {
 192         setid3v1title(fd, entry);
 193     }
 194
 195     if(!entry->length || (entry->filesize < 8 ))
 196         /* no song length or less than 8 bytes is hereby considered to be an
 197            invalid mp3 and won't be played by us! */
 198         return false;
 199
 200     return true;
 201 }