apps/metadata/mp4.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2005 Magnus Holmgren
  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 #include <stdio.h>
  22 #include <string.h>
  23 #include <stdlib.h>
  24 #include <ctype.h>
  25 #include <inttypes.h>
  26
  27 #include "system.h"
  28 #include "errno.h"
  29 #include "metadata.h"
  30 #include "metadata_common.h"
  31 #include "metadata_parsers.h"
  32 #include "logf.h"
  33 #include "debug.h"
  34 #include "replaygain.h"
  35
  36 #define MP4_3gp6 FOURCC('3', 'g', 'p', '6')
  37 #define MP4_aART FOURCC('a', 'A', 'R', 'T')
  38 #define MP4_alac FOURCC('a', 'l', 'a', 'c')
  39 #define MP4_calb FOURCC(0xa9, 'a', 'l', 'b')
  40 #define MP4_cART FOURCC(0xa9, 'A', 'R', 'T')
  41 #define MP4_cgrp FOURCC(0xa9, 'g', 'r', 'p')
  42 #define MP4_cgen FOURCC(0xa9, 'g', 'e', 'n')
  43 #define MP4_chpl FOURCC('c', 'h', 'p', 'l')
  44 #define MP4_cnam FOURCC(0xa9, 'n', 'a', 'm')
  45 #define MP4_cwrt FOURCC(0xa9, 'w', 'r', 't')
  46 #define MP4_ccmt FOURCC(0xa9, 'c', 'm', 't')
  47 #define MP4_cday FOURCC(0xa9, 'd', 'a', 'y')
  48 #define MP4_disk FOURCC('d', 'i', 's', 'k')
  49 #define MP4_esds FOURCC('e', 's', 'd', 's')
  50 #define MP4_ftyp FOURCC('f', 't', 'y', 'p')
  51 #define MP4_gnre FOURCC('g', 'n', 'r', 'e')
  52 #define MP4_hdlr FOURCC('h', 'd', 'l', 'r')
  53 #define MP4_ilst FOURCC('i', 'l', 's', 't')
  54 #define MP4_isom FOURCC('i', 's', 'o', 'm')
  55 #define MP4_M4A  FOURCC('M', '4', 'A', ' ')
  56 #define MP4_m4a  FOURCC('m', '4', 'a', ' ') /*technically its "M4A "*/
  57 #define MP4_M4B  FOURCC('M', '4', 'B', ' ') /*but files exist with lower case*/
  58 #define MP4_mdat FOURCC('m', 'd', 'a', 't')
  59 #define MP4_mdia FOURCC('m', 'd', 'i', 'a')
  60 #define MP4_mdir FOURCC('m', 'd', 'i', 'r')
  61 #define MP4_meta FOURCC('m', 'e', 't', 'a')
  62 #define MP4_minf FOURCC('m', 'i', 'n', 'f')
  63 #define MP4_moov FOURCC('m', 'o', 'o', 'v')
  64 #define MP4_mp4a FOURCC('m', 'p', '4', 'a')
  65 #define MP4_mp42 FOURCC('m', 'p', '4', '2')
  66 #define MP4_qt   FOURCC('q', 't', ' ', ' ')
  67 #define MP4_soun FOURCC('s', 'o', 'u', 'n')
  68 #define MP4_stbl FOURCC('s', 't', 'b', 'l')
  69 #define MP4_stsd FOURCC('s', 't', 's', 'd')
  70 #define MP4_stts FOURCC('s', 't', 't', 's')
  71 #define MP4_trak FOURCC('t', 'r', 'a', 'k')
  72 #define MP4_trkn FOURCC('t', 'r', 'k', 'n')
  73 #define MP4_udta FOURCC('u', 'd', 't', 'a')
  74 #define MP4_extra FOURCC('-', '-', '-', '-')
  75
  76 /* Read the tag data from an MP4 file, storing up to buffer_size bytes in
  77  * buffer.
  78  */
  79 static unsigned long read_mp4_tag(int fd, unsigned int size_left, char* buffer,
  80                                   unsigned int buffer_left)
  81 {
  82     unsigned int bytes_read = 0;
  83
  84     if (buffer_left == 0)
  85     {
  86         lseek(fd, size_left, SEEK_CUR);     /* Skip everything */
  87     }
  88     else
  89     {
  90         /* Skip the data tag header - maybe we should parse it properly? */
  91         lseek(fd, 16, SEEK_CUR);
  92         size_left -= 16;
  93
  94         if (size_left > buffer_left)
  95         {
  96             read(fd, buffer, buffer_left);
  97             lseek(fd, size_left - buffer_left, SEEK_CUR);
  98             bytes_read = buffer_left;
  99         }
 100         else
 101         {
 102             read(fd, buffer, size_left);
 103             bytes_read = size_left;
 104         }
 105     }
 106
 107     return bytes_read;
 108 }
 109
 110 /* Read a string tag from an MP4 file */
 111 static unsigned int read_mp4_tag_string(int fd, int size_left, char** buffer,
 112                                         unsigned int* buffer_left, char** dest)
 113 {
 114     unsigned int bytes_read = read_mp4_tag(fd, size_left, *buffer,
 115         *buffer_left > 0 ? *buffer_left - 1 : 0);
 116     unsigned int length = 0;
 117
 118     if (bytes_read)
 119     {
 120         (*buffer)[bytes_read] = 0;
 121         *dest = *buffer;
 122         length = strlen(*buffer) + 1;
 123         *buffer_left -= length;
 124         *buffer += length;
 125     }
 126     else
 127     {
 128         *dest = NULL;
 129     }
 130
 131     return length;
 132 }
 133
 134 static unsigned int read_mp4_atom(int fd, uint32_t* size,
 135                                   uint32_t* type, uint32_t size_left)
 136 {
 137     read_uint32be(fd, size);
 138     read_uint32be(fd, type);
 139
 140     if (*size == 1)
 141     {
 142         /* FAT32 doesn't support files this big, so something seems to
 143          * be wrong. (64-bit sizes should only be used when required.)
 144          */
 145         errno = EFBIG;
 146         *type = 0;
 147         return 0;
 148     }
 149
 150     if (*size > 0)
 151     {
 152         if (*size > size_left)
 153         {
 154             size_left = 0;
 155         }
 156         else
 157         {
 158             size_left -= *size;
 159         }
 160
 161         *size -= 8;
 162     }
 163     else
 164     {
 165         *size = size_left;
 166         size_left = 0;
 167     }
 168
 169     return size_left;
 170 }
 171
 172 static unsigned int read_mp4_length(int fd, uint32_t* size)
 173 {
 174     unsigned int length = 0;
 175     int bytes = 0;
 176     unsigned char c;
 177
 178     do
 179     {
 180         read(fd, &c, 1);
 181         bytes++;
 182         (*size)--;
 183         length = (length << 7) | (c & 0x7F);
 184     }
 185     while ((c & 0x80) && (bytes < 4) && (*size > 0));
 186
 187     return length;
 188 }
 189
 190 static bool read_mp4_esds(int fd, struct mp3entry* id3, uint32_t* size)
 191 {
 192     unsigned char buf[8];
 193     bool sbr = false;
 194
 195     lseek(fd, 4, SEEK_CUR);     /* Version and flags. */
 196     read(fd, buf, 1);           /* Verify ES_DescrTag. */
 197     *size -= 5;
 198
 199     if (*buf == 3)
 200     {
 201         /* read length */
 202         if (read_mp4_length(fd, size) < 20)
 203         {
 204             return sbr;
 205         }
 206
 207         lseek(fd, 3, SEEK_CUR);
 208         *size -= 3;
 209     }
 210     else
 211     {
 212         lseek(fd, 2, SEEK_CUR);
 213         *size -= 2;
 214     }
 215
 216     read(fd, buf, 1);           /* Verify DecoderConfigDescrTab. */
 217     *size -= 1;
 218
 219     if (*buf != 4)
 220     {
 221         return sbr;
 222     }
 223
 224     if (read_mp4_length(fd, size) < 13)
 225     {
 226         return sbr;
 227     }
 228
 229     lseek(fd, 13, SEEK_CUR);    /* Skip audio type, bit rates, etc. */
 230     read(fd, buf, 1);
 231     *size -= 14;
 232
 233     if (*buf != 5)              /* Verify DecSpecificInfoTag. */
 234     {
 235         return sbr;
 236     }
 237
 238     {
 239         static const int sample_rates[] =
 240         {
 241             96000, 88200, 64000, 48000, 44100, 32000,
 242             24000, 22050, 16000, 12000, 11025, 8000
 243         };
 244         unsigned long bits;
 245         unsigned int length;
 246         unsigned int index;
 247         unsigned int type;
 248
 249         /* Read the (leading part of the) decoder config. */
 250         length = read_mp4_length(fd, size);
 251         length = MIN(length, *size);
 252         length = MIN(length, sizeof(buf));
 253         memset(buf, 0, sizeof(buf));
 254         read(fd, buf, length);
 255         *size -= length;
 256
 257         /* Maybe time to write a simple read_bits function... */
 258
 259         /* Decoder config format:
 260          * Object type           - 5 bits
 261          * Frequency index       - 4 bits
 262          * Channel configuration - 4 bits
 263          */
 264         bits = get_long_be(buf);
 265         type = bits >> 27;              /* Object type - 5 bits */
 266         index = (bits >> 23) & 0xf;     /* Frequency index - 4 bits */
 267
 268         if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 269         {
 270             id3->frequency = sample_rates[index];
 271         }
 272
 273         if (type == 5)
 274         {
 275             unsigned int old_index = index;
 276
 277             sbr = true;
 278             index = (bits >> 15) & 0xf; /* Frequency index - 4 bits */
 279
 280             if (index == 15)
 281             {
 282                 /* 17 bits read so far... */
 283                 bits = get_long_be(&buf[2]);
 284                 id3->frequency = (bits >> 7) & 0x00ffffff;
 285             }
 286             else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 287             {
 288                 id3->frequency = sample_rates[index];
 289             }
 290
 291             if (old_index == index)
 292             {
 293                 /* Downsampled SBR */
 294                 id3->frequency *= 2;
 295             }
 296         }
 297         /* Skip 13 bits from above, plus 3 bits, then read 11 bits */
 298         else if ((length >= 4) && (((bits >> 5) & 0x7ff) == 0x2b7))
 299         {
 300             /* We found an extensionAudioObjectType */
 301             type = bits & 0x1f;         /* Object type - 5 bits*/
 302             bits = get_long_be(&buf[4]);
 303
 304             if (type == 5)
 305             {
 306                 sbr = bits >> 31;
 307
 308                 if (sbr)
 309                 {
 310                     unsigned int old_index = index;
 311
 312                     /* 1 bit read so far */
 313                     index = (bits >> 27) & 0xf; /* Frequency index - 4 bits */
 314
 315                     if (index == 15)
 316                     {
 317                         /* 5 bits read so far */
 318                         id3->frequency = (bits >> 3) & 0x00ffffff;
 319                     }
 320                     else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 321                     {
 322                         id3->frequency = sample_rates[index];
 323                     }
 324
 325                     if (old_index == index)
 326                     {
 327                         /* Downsampled SBR */
 328                         id3->frequency *= 2;
 329                     }
 330                 }
 331             }
 332         }
 333
 334         if (!sbr && (id3->frequency <= 24000) && (length <= 2))
 335         {
 336             /* Double the frequency for low-frequency files without a "long"
 337              * DecSpecificConfig header. The file may or may not contain SBR,
 338              * but here we guess it does if the header is short. This can
 339              * fail on some files, but it's the best we can do, short of
 340              * decoding (parts of) the file.
 341              */
 342             id3->frequency *= 2;
 343             sbr = true;
 344         }
 345     }
 346
 347     return sbr;
 348 }
 349
 350 static bool read_mp4_tags(int fd, struct mp3entry* id3,
 351                           uint32_t size_left)
 352 {
 353     uint32_t size;
 354     uint32_t type;
 355     unsigned int buffer_left = sizeof(id3->id3v2buf) + sizeof(id3->id3v1buf);
 356     char* buffer = id3->id3v2buf;
 357     bool cwrt = false;
 358
 359     do
 360     {
 361         size_left = read_mp4_atom(fd, &size, &type, size_left);
 362
 363         /* DEBUGF("Tag atom: '%c%c%c%c' (%d bytes left)\n", type >> 24 & 0xff,
 364             type >> 16 & 0xff, type >> 8 & 0xff, type & 0xff, size); */
 365
 366         switch (type)
 367         {
 368         case MP4_cnam:
 369             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 370                 &id3->title);
 371             break;
 372
 373         case MP4_cART:
 374             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 375                 &id3->artist);
 376             break;
 377
 378         case MP4_aART:
 379             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 380                 &id3->albumartist);
 381             break;
 382
 383         case MP4_cgrp:
 384             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 385                 &id3->grouping);
 386             break;
 387
 388         case MP4_calb:
 389             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 390                 &id3->album);
 391             break;
 392
 393         case MP4_cwrt:
 394             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 395                 &id3->composer);
 396             cwrt = false;
 397             break;
 398
 399         case MP4_ccmt:
 400             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 401                 &id3->comment);
 402             break;
 403
 404         case MP4_cday:
 405             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 406                                 &id3->year_string);
 407
 408             /* Try to parse it as a year, for the benefit of the database.
 409              */
 410             if(id3->year_string)
 411             {
 412                 id3->year = atoi(id3->year_string);
 413                 if (id3->year < 1900)
 414                 {
 415                     id3->year = 0;
 416                 }
 417             }
 418             else
 419                 id3->year = 0;
 420
 421             break;
 422
 423         case MP4_gnre:
 424             {
 425                 unsigned short genre;
 426
 427                 read_mp4_tag(fd, size, (char*) &genre, sizeof(genre));
 428                 id3->genre_string = id3_get_num_genre(betoh16(genre) - 1);
 429             }
 430             break;
 431
 432         case MP4_cgen:
 433             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 434                 &id3->genre_string);
 435             break;
 436
 437         case MP4_disk:
 438             {
 439                 unsigned short n[2];
 440
 441                 read_mp4_tag(fd, size, (char*) &n, sizeof(n));
 442                 id3->discnum = betoh16(n[1]);
 443             }
 444             break;
 445
 446         case MP4_trkn:
 447             {
 448                 unsigned short n[2];
 449
 450                 read_mp4_tag(fd, size, (char*) &n, sizeof(n));
 451                 id3->tracknum = betoh16(n[1]);
 452             }
 453             break;
 454
 455         case MP4_extra:
 456             {
 457                 char tag_name[TAG_NAME_LENGTH];
 458                 uint32_t sub_size;
 459
 460                 /* "mean" atom */
 461                 read_uint32be(fd, &sub_size);
 462                 size -= sub_size;
 463                 lseek(fd, sub_size - 4, SEEK_CUR);
 464                 /* "name" atom */
 465                 read_uint32be(fd, &sub_size);
 466                 size -= sub_size;
 467                 lseek(fd, 8, SEEK_CUR);
 468                 sub_size -= 12;
 469
 470                 if (sub_size > sizeof(tag_name) - 1)
 471                 {
 472                     read(fd, tag_name, sizeof(tag_name) - 1);
 473                     lseek(fd, sub_size - (sizeof(tag_name) - 1), SEEK_CUR);
 474                     tag_name[sizeof(tag_name) - 1] = 0;
 475                 }
 476                 else
 477                 {
 478                     read(fd, tag_name, sub_size);
 479                     tag_name[sub_size] = 0;
 480                 }
 481
 482                 if ((strcasecmp(tag_name, "composer") == 0) && !cwrt)
 483                 {
 484                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 485                         &id3->composer);
 486                 }
 487                 else if (strcasecmp(tag_name, "iTunSMPB") == 0)
 488                 {
 489                     char value[TAG_VALUE_LENGTH];
 490                     char* value_p = value;
 491                     char* any;
 492                     unsigned int length = sizeof(value);
 493
 494                     read_mp4_tag_string(fd, size, &value_p, &length, &any);
 495                     id3->lead_trim = get_itunes_int32(value, 1);
 496                     id3->tail_trim = get_itunes_int32(value, 2);
 497                     DEBUGF("AAC: lead_trim %d, tail_trim %d\n",
 498                         id3->lead_trim, id3->tail_trim);
 499                 }
 500                 else if (strcasecmp(tag_name, "musicbrainz track id") == 0)
 501                 {
 502                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 503                         &id3->mb_track_id);
 504                 }
 505                 else if ((strcasecmp(tag_name, "album artist") == 0))
 506                 {
 507                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 508                         &id3->albumartist);
 509                 }
 510                 else
 511                 {
 512                     char* any;
 513                     unsigned int length = read_mp4_tag_string(fd, size,
 514                         &buffer, &buffer_left, &any);
 515
 516                     if (length > 0)
 517                     {
 518                         /* Re-use the read buffer as the dest buffer... */
 519                         buffer -= length;
 520                         buffer_left += length;
 521
 522                         if (parse_replaygain(tag_name, buffer, id3,
 523                             buffer, buffer_left) > 0)
 524                         {
 525                             /* Data used, keep it. */
 526                             buffer += length;
 527                             buffer_left -= length;
 528                         }
 529                     }
 530                 }
 531             }
 532             break;
 533
 534         default:
 535             lseek(fd, size, SEEK_CUR);
 536             break;
 537         }
 538     }
 539     while ((size_left > 0) && (errno == 0));
 540
 541     return true;
 542 }
 543
 544 static bool read_mp4_container(int fd, struct mp3entry* id3,
 545                                uint32_t size_left)
 546 {
 547     uint32_t size    = 0;
 548     uint32_t type    = 0;
 549     uint32_t handler = 0;
 550     bool rc = true;
 551     bool done = false;
 552
 553     do
 554     {
 555         size_left = read_mp4_atom(fd, &size, &type, size_left);
 556
 557         /* DEBUGF("Atom: '%c%c%c%c' (0x%08lx, %lu bytes left)\n",
 558             (int) ((type >> 24) & 0xff), (int) ((type >> 16) & 0xff),
 559             (int) ((type >> 8) & 0xff), (int) (type & 0xff),
 560             type, size); */
 561
 562         switch (type)
 563         {
 564         case MP4_ftyp:
 565             {
 566                 uint32_t id;
 567
 568                 read_uint32be(fd, &id);
 569                 size -= 4;
 570
 571                 if ((id != MP4_M4A) && (id != MP4_M4B) && (id != MP4_mp42)
 572                     && (id != MP4_qt) && (id != MP4_3gp6) && (id != MP4_m4a)
 573                     && (id != MP4_isom))
 574                 {
 575                     DEBUGF("Unknown MP4 file type: '%c%c%c%c'\n",
 576                         (int)(id >> 24 & 0xff), (int)(id >> 16 & 0xff),
 577                         (int)(id >> 8 & 0xff), (int)(id & 0xff));
 578                     return false;
 579                 }
 580             }
 581             break;
 582
 583         case MP4_meta:
 584             lseek(fd, 4, SEEK_CUR);  /* Skip version */
 585             size -= 4;
 586             /* Fall through */
 587
 588         case MP4_moov:
 589         case MP4_udta:
 590         case MP4_mdia:
 591         case MP4_stbl:
 592         case MP4_trak:
 593             rc = read_mp4_container(fd, id3, size);
 594             size = 0;
 595             break;
 596
 597         case MP4_ilst:
 598             /* We need at least a size of 8 to read the next atom. */
 599             if (handler == MP4_mdir && size>8)
 600             {
 601                 rc = read_mp4_tags(fd, id3, size);
 602                 size = 0;
 603             }
 604             break;
 605
 606         case MP4_minf:
 607             if (handler == MP4_soun)
 608             {
 609                 rc = read_mp4_container(fd, id3, size);
 610                 size = 0;
 611             }
 612             break;
 613
 614         case MP4_stsd:
 615             lseek(fd, 8, SEEK_CUR);
 616             size -= 8;
 617             rc = read_mp4_container(fd, id3, size);
 618             size = 0;
 619             break;
 620
 621         case MP4_hdlr:
 622             lseek(fd, 8, SEEK_CUR);
 623             read_uint32be(fd, &handler);
 624             size -= 12;
 625             /* DEBUGF("    Handler '%c%c%c%c'\n", handler >> 24 & 0xff,
 626                 handler >> 16 & 0xff, handler >> 8 & 0xff,handler & 0xff); */
 627             break;
 628
 629         case MP4_stts:
 630             {
 631                 uint32_t entries;
 632                 unsigned int i;
 633
 634                 /* Reset to false. */
 635                 id3->needs_upsampling_correction = false;
 636
 637                 lseek(fd, 4, SEEK_CUR);
 638                 read_uint32be(fd, &entries);
 639                 id3->samples = 0;
 640
 641                 for (i = 0; i < entries; i++)
 642                 {
 643                     uint32_t n;
 644                     uint32_t l;
 645
 646                     read_uint32be(fd, &n);
 647                     read_uint32be(fd, &l);
 648
 649                     /* Some AAC file use HE profile. In this case the number
 650                      * of output samples is doubled to a maximum of 2048
 651                      * samples per frame. This means that files which already
 652                      * report a frame size of 2048 in their header will not
 653                      * need any further special handling. */
 654                     if (id3->codectype==AFMT_MP4_AAC_HE && l<=1024)
 655                     {
 656                         id3->samples += n * l * 2;
 657                         id3->needs_upsampling_correction = true;
 658                     }
 659                     else
 660                     {
 661                         id3->samples += n * l;
 662                     }
 663                 }
 664
 665                 size = 0;
 666             }
 667             break;
 668
 669         case MP4_mp4a:
 670             {
 671                 uint32_t subsize;
 672                 uint32_t subtype;
 673
 674                 /* Move to the next expected mp4 atom. */
 675                 lseek(fd, 28, SEEK_CUR);
 676                 read_mp4_atom(fd, &subsize, &subtype, size);
 677                 size -= 36;
 678
 679                 if (subtype == MP4_esds)
 680                 {
 681                     /* Read esds metadata and return if AAC-HE/SBR is used. */
 682                     if (read_mp4_esds(fd, id3, &size))
 683                         id3->codectype = AFMT_MP4_AAC_HE;
 684                     else
 685                         id3->codectype = AFMT_MP4_AAC;
 686                 }
 687             }
 688             break;
 689
 690         case MP4_alac:
 691             {
 692                 uint32_t frequency;
 693                 uint32_t subsize;
 694                 uint32_t subtype;
 695
 696                 /* Move to the next expected mp4 atom. */
 697                 lseek(fd, 28, SEEK_CUR);
 698                 read_mp4_atom(fd, &subsize, &subtype, size);
 699                 size -= 36;
 700 #if 0
 701                 /* We might need to parse for the alac metadata atom. */
 702                 while (!((subsize==28) && (subtype==MP4_alac)) && (size>0))
 703                 {
 704                     lseek(fd, -7, SEEK_CUR);
 705                     read_mp4_atom(fd, &subsize, &subtype, size);
 706                     size -= 1;
 707                     errno = 0; /* will most likely be set while parsing */
 708                 }
 709 #endif
 710                 if (subtype == MP4_alac)
 711                 {
 712                     lseek(fd, 24, SEEK_CUR);
 713                     read_uint32be(fd, &frequency);
 714                     size -= 28;
 715                     id3->frequency = frequency;
 716                     id3->codectype = AFMT_MP4_ALAC;
 717                 }
 718             }
 719             break;
 720
 721         case MP4_mdat:
 722             /* Some AAC files appear to contain additional empty mdat chunks.
 723                Ignore them. */
 724             if(size == 0)
 725                 break;
 726             id3->filesize = size;
 727             if(id3->samples > 0) {
 728                 /* We've already seen the moov chunk. */
 729                 done = true;
 730             }
 731             break;
 732
 733         case MP4_chpl:
 734             {
 735                 /* ADDME: add support for real chapters. Right now it's only
 736                  * used for Nero's gapless hack */
 737                 uint8_t chapters;
 738                 uint64_t timestamp;
 739
 740                 lseek(fd, 8, SEEK_CUR);
 741                 read_uint8(fd, &chapters);
 742                 size -= 9;
 743
 744                 /* the first chapter will be used as the lead_trim */
 745                 if (chapters > 0) {
 746                     read_uint64be(fd, &timestamp);
 747                     id3->lead_trim = (timestamp * id3->frequency) / 10000000;
 748                     size -= 8;
 749                 }
 750             }
 751             break;
 752
 753         default:
 754             break;
 755         }
 756
 757         /* Skip final seek. */
 758         if (!done)
 759         {
 760             lseek(fd, size, SEEK_CUR);
 761         }
 762     } while (rc && (size_left > 0) && (errno == 0) && !done);
 763
 764     return rc;
 765 }
 766
 767 bool get_mp4_metadata(int fd, struct mp3entry* id3)
 768 {
 769     id3->codectype = AFMT_UNKNOWN;
 770     id3->filesize = 0;
 771     errno = 0;
 772
 773     if (read_mp4_container(fd, id3, filesize(fd)) && (errno == 0)
 774         && (id3->samples > 0) && (id3->frequency > 0)
 775         && (id3->filesize > 0))
 776     {
 777         if (id3->codectype == AFMT_UNKNOWN)
 778         {
 779             logf("Not an ALAC or AAC file");
 780             return false;
 781         }
 782
 783         id3->length = ((int64_t) id3->samples * 1000) / id3->frequency;
 784
 785         id3->vbr = true; /* ALAC is native VBR, AAC very unlikely is CBR. */
 786
 787         if (id3->length <= 0)
 788         {
 789             logf("mp4 length invalid!");
 790             return false;
 791         }
 792
 793         id3->bitrate = ((int64_t) id3->filesize * 8) / id3->length;
 794         DEBUGF("MP4 bitrate %d, frequency %ld Hz, length %ld ms\n",
 795             id3->bitrate, id3->frequency, id3->length);
 796     }
 797     else
 798     {
 799         logf("MP4 metadata error");
 800         DEBUGF("MP4 metadata error. errno %d, samples %ld, frequency %ld, "
 801             "filesize %ld\n", errno, id3->samples, id3->frequency,
 802             id3->filesize);
 803         return false;
 804     }
 805
 806     return true;
 807 }