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         /* Do not overwrite already available metadata. Especially when reading
 121          * tags with e.g. multiple genres / artists. This way only the first
 122          * of multiple entries is used, all following are dropped. */
 123         if (*dest == NULL)
 124         {
 125             (*buffer)[bytes_read] = 0; /* zero-terminate for correct strlen().*/
 126             length = strlen(*buffer) + 1;
 127             length = MIN(length, ID3V2_MAX_ITEM_SIZE); /* Limit item size. */
 128
 129             *dest = *buffer;
 130             (*buffer)[length-1] = 0; /* zero-terminate buffer. */
 131             *buffer_left -= length;
 132             *buffer += length;
 133         }
 134     }
 135     else
 136     {
 137         *dest = NULL;
 138     }
 139
 140     return length;
 141 }
 142
 143 static unsigned int read_mp4_atom(int fd, uint32_t* size,
 144                                   uint32_t* type, uint32_t size_left)
 145 {
 146     read_uint32be(fd, size);
 147     read_uint32be(fd, type);
 148
 149     if (*size == 1)
 150     {
 151         /* FAT32 doesn't support files this big, so something seems to
 152          * be wrong. (64-bit sizes should only be used when required.)
 153          */
 154         errno = EFBIG;
 155         *type = 0;
 156         return 0;
 157     }
 158
 159     if (*size > 0)
 160     {
 161         if (*size > size_left)
 162         {
 163             size_left = 0;
 164         }
 165         else
 166         {
 167             size_left -= *size;
 168         }
 169
 170         *size -= 8;
 171     }
 172     else
 173     {
 174         *size = size_left;
 175         size_left = 0;
 176     }
 177
 178     return size_left;
 179 }
 180
 181 static unsigned int read_mp4_length(int fd, uint32_t* size)
 182 {
 183     unsigned int length = 0;
 184     int bytes = 0;
 185     unsigned char c;
 186
 187     do
 188     {
 189         read(fd, &c, 1);
 190         bytes++;
 191         (*size)--;
 192         length = (length << 7) | (c & 0x7F);
 193     }
 194     while ((c & 0x80) && (bytes < 4) && (*size > 0));
 195
 196     return length;
 197 }
 198
 199 static bool read_mp4_esds(int fd, struct mp3entry* id3, uint32_t* size)
 200 {
 201     unsigned char buf[8];
 202     bool sbr = false;
 203
 204     lseek(fd, 4, SEEK_CUR);     /* Version and flags. */
 205     read(fd, buf, 1);           /* Verify ES_DescrTag. */
 206     *size -= 5;
 207
 208     if (*buf == 3)
 209     {
 210         /* read length */
 211         if (read_mp4_length(fd, size) < 20)
 212         {
 213             return sbr;
 214         }
 215
 216         lseek(fd, 3, SEEK_CUR);
 217         *size -= 3;
 218     }
 219     else
 220     {
 221         lseek(fd, 2, SEEK_CUR);
 222         *size -= 2;
 223     }
 224
 225     read(fd, buf, 1);           /* Verify DecoderConfigDescrTab. */
 226     *size -= 1;
 227
 228     if (*buf != 4)
 229     {
 230         return sbr;
 231     }
 232
 233     if (read_mp4_length(fd, size) < 13)
 234     {
 235         return sbr;
 236     }
 237
 238     lseek(fd, 13, SEEK_CUR);    /* Skip audio type, bit rates, etc. */
 239     read(fd, buf, 1);
 240     *size -= 14;
 241
 242     if (*buf != 5)              /* Verify DecSpecificInfoTag. */
 243     {
 244         return sbr;
 245     }
 246
 247     {
 248         static const int sample_rates[] =
 249         {
 250             96000, 88200, 64000, 48000, 44100, 32000,
 251             24000, 22050, 16000, 12000, 11025, 8000
 252         };
 253         unsigned long bits;
 254         unsigned int length;
 255         unsigned int index;
 256         unsigned int type;
 257
 258         /* Read the (leading part of the) decoder config. */
 259         length = read_mp4_length(fd, size);
 260         length = MIN(length, *size);
 261         length = MIN(length, sizeof(buf));
 262         memset(buf, 0, sizeof(buf));
 263         read(fd, buf, length);
 264         *size -= length;
 265
 266         /* Maybe time to write a simple read_bits function... */
 267
 268         /* Decoder config format:
 269          * Object type           - 5 bits
 270          * Frequency index       - 4 bits
 271          * Channel configuration - 4 bits
 272          */
 273         bits = get_long_be(buf);
 274         type = bits >> 27;              /* Object type - 5 bits */
 275         index = (bits >> 23) & 0xf;     /* Frequency index - 4 bits */
 276
 277         if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 278         {
 279             id3->frequency = sample_rates[index];
 280         }
 281
 282         if (type == 5)
 283         {
 284             unsigned int old_index = index;
 285
 286             sbr = true;
 287             index = (bits >> 15) & 0xf; /* Frequency index - 4 bits */
 288
 289             if (index == 15)
 290             {
 291                 /* 17 bits read so far... */
 292                 bits = get_long_be(&buf[2]);
 293                 id3->frequency = (bits >> 7) & 0x00ffffff;
 294             }
 295             else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 296             {
 297                 id3->frequency = sample_rates[index];
 298             }
 299
 300             if (old_index == index)
 301             {
 302                 /* Downsampled SBR */
 303                 id3->frequency *= 2;
 304             }
 305         }
 306         /* Skip 13 bits from above, plus 3 bits, then read 11 bits */
 307         else if ((length >= 4) && (((bits >> 5) & 0x7ff) == 0x2b7))
 308         {
 309             /* We found an extensionAudioObjectType */
 310             type = bits & 0x1f;         /* Object type - 5 bits*/
 311             bits = get_long_be(&buf[4]);
 312
 313             if (type == 5)
 314             {
 315                 sbr = bits >> 31;
 316
 317                 if (sbr)
 318                 {
 319                     unsigned int old_index = index;
 320
 321                     /* 1 bit read so far */
 322                     index = (bits >> 27) & 0xf; /* Frequency index - 4 bits */
 323
 324                     if (index == 15)
 325                     {
 326                         /* 5 bits read so far */
 327                         id3->frequency = (bits >> 3) & 0x00ffffff;
 328                     }
 329                     else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 330                     {
 331                         id3->frequency = sample_rates[index];
 332                     }
 333
 334                     if (old_index == index)
 335                     {
 336                         /* Downsampled SBR */
 337                         id3->frequency *= 2;
 338                     }
 339                 }
 340             }
 341         }
 342
 343         if (!sbr && (id3->frequency <= 24000) && (length <= 2))
 344         {
 345             /* Double the frequency for low-frequency files without a "long"
 346              * DecSpecificConfig header. The file may or may not contain SBR,
 347              * but here we guess it does if the header is short. This can
 348              * fail on some files, but it's the best we can do, short of
 349              * decoding (parts of) the file.
 350              */
 351             id3->frequency *= 2;
 352             sbr = true;
 353         }
 354     }
 355
 356     return sbr;
 357 }
 358
 359 static bool read_mp4_tags(int fd, struct mp3entry* id3,
 360                           uint32_t size_left)
 361 {
 362     uint32_t size;
 363     uint32_t type;
 364     unsigned int buffer_left = sizeof(id3->id3v2buf) + sizeof(id3->id3v1buf);
 365     char* buffer = id3->id3v2buf;
 366     bool cwrt = false;
 367
 368     do
 369     {
 370         size_left = read_mp4_atom(fd, &size, &type, size_left);
 371
 372         /* DEBUGF("Tag atom: '%c%c%c%c' (%d bytes left)\n", type >> 24 & 0xff,
 373             type >> 16 & 0xff, type >> 8 & 0xff, type & 0xff, size); */
 374
 375         switch (type)
 376         {
 377         case MP4_cnam:
 378             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 379                 &id3->title);
 380             break;
 381
 382         case MP4_cART:
 383             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 384                 &id3->artist);
 385             break;
 386
 387         case MP4_aART:
 388             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 389                 &id3->albumartist);
 390             break;
 391
 392         case MP4_cgrp:
 393             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 394                 &id3->grouping);
 395             break;
 396
 397         case MP4_calb:
 398             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 399                 &id3->album);
 400             break;
 401
 402         case MP4_cwrt:
 403             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 404                 &id3->composer);
 405             cwrt = false;
 406             break;
 407
 408         case MP4_ccmt:
 409             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 410                 &id3->comment);
 411             break;
 412
 413         case MP4_cday:
 414             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 415                                 &id3->year_string);
 416
 417             /* Try to parse it as a year, for the benefit of the database.
 418              */
 419             if(id3->year_string)
 420             {
 421                 id3->year = atoi(id3->year_string);
 422                 if (id3->year < 1900)
 423                 {
 424                     id3->year = 0;
 425                 }
 426             }
 427             else
 428                 id3->year = 0;
 429
 430             break;
 431
 432         case MP4_gnre:
 433             {
 434                 unsigned short genre;
 435
 436                 read_mp4_tag(fd, size, (char*) &genre, sizeof(genre));
 437                 id3->genre_string = id3_get_num_genre(betoh16(genre) - 1);
 438             }
 439             break;
 440
 441         case MP4_cgen:
 442             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 443                 &id3->genre_string);
 444             break;
 445
 446         case MP4_disk:
 447             {
 448                 unsigned short n[2];
 449
 450                 read_mp4_tag(fd, size, (char*) &n, sizeof(n));
 451                 id3->discnum = betoh16(n[1]);
 452             }
 453             break;
 454
 455         case MP4_trkn:
 456             {
 457                 unsigned short n[2];
 458
 459                 read_mp4_tag(fd, size, (char*) &n, sizeof(n));
 460                 id3->tracknum = betoh16(n[1]);
 461             }
 462             break;
 463
 464         case MP4_extra:
 465             {
 466                 char tag_name[TAG_NAME_LENGTH];
 467                 uint32_t sub_size;
 468
 469                 /* "mean" atom */
 470                 read_uint32be(fd, &sub_size);
 471                 size -= sub_size;
 472                 lseek(fd, sub_size - 4, SEEK_CUR);
 473                 /* "name" atom */
 474                 read_uint32be(fd, &sub_size);
 475                 size -= sub_size;
 476                 lseek(fd, 8, SEEK_CUR);
 477                 sub_size -= 12;
 478
 479                 if (sub_size > sizeof(tag_name) - 1)
 480                 {
 481                     read(fd, tag_name, sizeof(tag_name) - 1);
 482                     lseek(fd, sub_size - (sizeof(tag_name) - 1), SEEK_CUR);
 483                     tag_name[sizeof(tag_name) - 1] = 0;
 484                 }
 485                 else
 486                 {
 487                     read(fd, tag_name, sub_size);
 488                     tag_name[sub_size] = 0;
 489                 }
 490
 491                 if ((strcasecmp(tag_name, "composer") == 0) && !cwrt)
 492                 {
 493                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 494                         &id3->composer);
 495                 }
 496                 else if (strcasecmp(tag_name, "iTunSMPB") == 0)
 497                 {
 498                     char value[TAG_VALUE_LENGTH];
 499                     char* value_p = value;
 500                     char* any;
 501                     unsigned int length = sizeof(value);
 502
 503                     read_mp4_tag_string(fd, size, &value_p, &length, &any);
 504                     id3->lead_trim = get_itunes_int32(value, 1);
 505                     id3->tail_trim = get_itunes_int32(value, 2);
 506                     DEBUGF("AAC: lead_trim %d, tail_trim %d\n",
 507                         id3->lead_trim, id3->tail_trim);
 508                 }
 509                 else if (strcasecmp(tag_name, "musicbrainz track id") == 0)
 510                 {
 511                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 512                         &id3->mb_track_id);
 513                 }
 514                 else if ((strcasecmp(tag_name, "album artist") == 0))
 515                 {
 516                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 517                         &id3->albumartist);
 518                 }
 519                 else
 520                 {
 521                     char* any = NULL;
 522                     unsigned int length = read_mp4_tag_string(fd, size,
 523                         &buffer, &buffer_left, &any);
 524
 525                     if (length > 0)
 526                     {
 527                         /* Re-use the read buffer as the dest buffer... */
 528                         buffer -= length;
 529                         buffer_left += length;
 530
 531                         parse_replaygain(tag_name, buffer, id3);
 532                     }
 533                 }
 534             }
 535             break;
 536
 537         default:
 538             lseek(fd, size, SEEK_CUR);
 539             break;
 540         }
 541     }
 542     while ((size_left > 0) && (errno == 0));
 543
 544     return true;
 545 }
 546
 547 static bool read_mp4_container(int fd, struct mp3entry* id3,
 548                                uint32_t size_left)
 549 {
 550     uint32_t size    = 0;
 551     uint32_t type    = 0;
 552     uint32_t handler = 0;
 553     bool rc = true;
 554     bool done = false;
 555
 556     do
 557     {
 558         size_left = read_mp4_atom(fd, &size, &type, size_left);
 559
 560         /* DEBUGF("Atom: '%c%c%c%c' (0x%08lx, %lu bytes left)\n",
 561             (int) ((type >> 24) & 0xff), (int) ((type >> 16) & 0xff),
 562             (int) ((type >> 8) & 0xff), (int) (type & 0xff),
 563             type, size); */
 564
 565         switch (type)
 566         {
 567         case MP4_ftyp:
 568             {
 569                 uint32_t id;
 570
 571                 read_uint32be(fd, &id);
 572                 size -= 4;
 573
 574                 if ((id != MP4_M4A) && (id != MP4_M4B) && (id != MP4_mp42)
 575                     && (id != MP4_qt) && (id != MP4_3gp6) && (id != MP4_m4a)
 576                     && (id != MP4_isom))
 577                 {
 578                     DEBUGF("Unknown MP4 file type: '%c%c%c%c'\n",
 579                         (int)(id >> 24 & 0xff), (int)(id >> 16 & 0xff),
 580                         (int)(id >> 8 & 0xff), (int)(id & 0xff));
 581                     return false;
 582                 }
 583             }
 584             break;
 585
 586         case MP4_meta:
 587             lseek(fd, 4, SEEK_CUR);  /* Skip version */
 588             size -= 4;
 589             /* Fall through */
 590
 591         case MP4_moov:
 592         case MP4_udta:
 593         case MP4_mdia:
 594         case MP4_stbl:
 595         case MP4_trak:
 596             rc = read_mp4_container(fd, id3, size);
 597             size = 0;
 598             break;
 599
 600         case MP4_ilst:
 601             /* We need at least a size of 8 to read the next atom. */
 602             if (handler == MP4_mdir && size>8)
 603             {
 604                 rc = read_mp4_tags(fd, id3, size);
 605                 size = 0;
 606             }
 607             break;
 608
 609         case MP4_minf:
 610             if (handler == MP4_soun)
 611             {
 612                 rc = read_mp4_container(fd, id3, size);
 613                 size = 0;
 614             }
 615             break;
 616
 617         case MP4_stsd:
 618             lseek(fd, 8, SEEK_CUR);
 619             size -= 8;
 620             rc = read_mp4_container(fd, id3, size);
 621             size = 0;
 622             break;
 623
 624         case MP4_hdlr:
 625             lseek(fd, 8, SEEK_CUR);
 626             read_uint32be(fd, &handler);
 627             size -= 12;
 628             /* DEBUGF("    Handler '%c%c%c%c'\n", handler >> 24 & 0xff,
 629                 handler >> 16 & 0xff, handler >> 8 & 0xff,handler & 0xff); */
 630             break;
 631
 632         case MP4_stts:
 633             {
 634                 uint32_t entries;
 635                 unsigned int i;
 636
 637                 /* Reset to false. */
 638                 id3->needs_upsampling_correction = false;
 639
 640                 lseek(fd, 4, SEEK_CUR);
 641                 read_uint32be(fd, &entries);
 642                 id3->samples = 0;
 643
 644                 for (i = 0; i < entries; i++)
 645                 {
 646                     uint32_t n;
 647                     uint32_t l;
 648
 649                     read_uint32be(fd, &n);
 650                     read_uint32be(fd, &l);
 651
 652                     /* Some AAC file use HE profile. In this case the number
 653                      * of output samples is doubled to a maximum of 2048
 654                      * samples per frame. This means that files which already
 655                      * report a frame size of 2048 in their header will not
 656                      * need any further special handling. */
 657                     if (id3->codectype==AFMT_MP4_AAC_HE && l<=1024)
 658                     {
 659                         id3->samples += n * l * 2;
 660                         id3->needs_upsampling_correction = true;
 661                     }
 662                     else
 663                     {
 664                         id3->samples += n * l;
 665                     }
 666                 }
 667
 668                 size = 0;
 669             }
 670             break;
 671
 672         case MP4_mp4a:
 673             {
 674                 uint32_t subsize;
 675                 uint32_t subtype;
 676
 677                 /* Move to the next expected mp4 atom. */
 678                 lseek(fd, 28, SEEK_CUR);
 679                 read_mp4_atom(fd, &subsize, &subtype, size);
 680                 size -= 36;
 681
 682                 if (subtype == MP4_esds)
 683                 {
 684                     /* Read esds metadata and return if AAC-HE/SBR is used. */
 685                     if (read_mp4_esds(fd, id3, &size))
 686                         id3->codectype = AFMT_MP4_AAC_HE;
 687                     else
 688                         id3->codectype = AFMT_MP4_AAC;
 689                 }
 690             }
 691             break;
 692
 693         case MP4_alac:
 694             {
 695                 uint32_t frequency;
 696                 uint32_t subsize;
 697                 uint32_t subtype;
 698
 699                 /* Move to the next expected mp4 atom. */
 700                 lseek(fd, 28, SEEK_CUR);
 701                 read_mp4_atom(fd, &subsize, &subtype, size);
 702                 size -= 36;
 703 #if 0
 704                 /* We might need to parse for the alac metadata atom. */
 705                 while (!((subsize==28) && (subtype==MP4_alac)) && (size>0))
 706                 {
 707                     lseek(fd, -7, SEEK_CUR);
 708                     read_mp4_atom(fd, &subsize, &subtype, size);
 709                     size -= 1;
 710                     errno = 0; /* will most likely be set while parsing */
 711                 }
 712 #endif
 713                 if (subtype == MP4_alac)
 714                 {
 715                     lseek(fd, 24, SEEK_CUR);
 716                     read_uint32be(fd, &frequency);
 717                     size -= 28;
 718                     id3->frequency = frequency;
 719                     id3->codectype = AFMT_MP4_ALAC;
 720                 }
 721             }
 722             break;
 723
 724         case MP4_mdat:
 725             /* Some AAC files appear to contain additional empty mdat chunks.
 726                Ignore them. */
 727             if(size == 0)
 728                 break;
 729             id3->filesize = size;
 730             if(id3->samples > 0) {
 731                 /* We've already seen the moov chunk. */
 732                 done = true;
 733             }
 734             break;
 735
 736         case MP4_chpl:
 737             {
 738                 /* ADDME: add support for real chapters. Right now it's only
 739                  * used for Nero's gapless hack */
 740                 uint8_t chapters;
 741                 uint64_t timestamp;
 742
 743                 lseek(fd, 8, SEEK_CUR);
 744                 read_uint8(fd, &chapters);
 745                 size -= 9;
 746
 747                 /* the first chapter will be used as the lead_trim */
 748                 if (chapters > 0) {
 749                     read_uint64be(fd, &timestamp);
 750                     id3->lead_trim = (timestamp * id3->frequency) / 10000000;
 751                     size -= 8;
 752                 }
 753             }
 754             break;
 755
 756         default:
 757             break;
 758         }
 759
 760         /* Skip final seek. */
 761         if (!done)
 762         {
 763             lseek(fd, size, SEEK_CUR);
 764         }
 765     } while (rc && (size_left > 0) && (errno == 0) && !done);
 766
 767     return rc;
 768 }
 769
 770 bool get_mp4_metadata(int fd, struct mp3entry* id3)
 771 {
 772     id3->codectype = AFMT_UNKNOWN;
 773     id3->filesize = 0;
 774     errno = 0;
 775
 776     if (read_mp4_container(fd, id3, filesize(fd)) && (errno == 0)
 777         && (id3->samples > 0) && (id3->frequency > 0)
 778         && (id3->filesize > 0))
 779     {
 780         if (id3->codectype == AFMT_UNKNOWN)
 781         {
 782             logf("Not an ALAC or AAC file");
 783             return false;
 784         }
 785
 786         id3->length = ((int64_t) id3->samples * 1000) / id3->frequency;
 787
 788         id3->vbr = true; /* ALAC is native VBR, AAC very unlikely is CBR. */
 789
 790         if (id3->length <= 0)
 791         {
 792             logf("mp4 length invalid!");
 793             return false;
 794         }
 795
 796         id3->bitrate = ((int64_t) id3->filesize * 8) / id3->length;
 797         DEBUGF("MP4 bitrate %d, frequency %ld Hz, length %ld ms\n",
 798             id3->bitrate, id3->frequency, id3->length);
 799     }
 800     else
 801     {
 802         logf("MP4 metadata error");
 803         DEBUGF("MP4 metadata error. errno %d, samples %ld, frequency %ld, "
 804             "filesize %ld\n", errno, id3->samples, id3->frequency,
 805             id3->filesize);
 806         return false;
 807     }
 808
 809     return true;
 810 }