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_M4A  FOURCC('M', '4', 'A', ' ')
  55 #define MP4_M4B  FOURCC('M', '4', 'B', ' ')
  56 #define MP4_mdat FOURCC('m', 'd', 'a', 't')
  57 #define MP4_mdia FOURCC('m', 'd', 'i', 'a')
  58 #define MP4_mdir FOURCC('m', 'd', 'i', 'r')
  59 #define MP4_meta FOURCC('m', 'e', 't', 'a')
  60 #define MP4_minf FOURCC('m', 'i', 'n', 'f')
  61 #define MP4_moov FOURCC('m', 'o', 'o', 'v')
  62 #define MP4_mp4a FOURCC('m', 'p', '4', 'a')
  63 #define MP4_mp42 FOURCC('m', 'p', '4', '2')
  64 #define MP4_qt   FOURCC('q', 't', ' ', ' ')
  65 #define MP4_soun FOURCC('s', 'o', 'u', 'n')
  66 #define MP4_stbl FOURCC('s', 't', 'b', 'l')
  67 #define MP4_stsd FOURCC('s', 't', 's', 'd')
  68 #define MP4_stts FOURCC('s', 't', 't', 's')
  69 #define MP4_trak FOURCC('t', 'r', 'a', 'k')
  70 #define MP4_trkn FOURCC('t', 'r', 'k', 'n')
  71 #define MP4_udta FOURCC('u', 'd', 't', 'a')
  72 #define MP4_extra FOURCC('-', '-', '-', '-')
  73
  74 /* Read the tag data from an MP4 file, storing up to buffer_size bytes in
  75  * buffer.
  76  */
  77 static unsigned long read_mp4_tag(int fd, unsigned int size_left, char* buffer,
  78                                   unsigned int buffer_left)
  79 {
  80     unsigned int bytes_read = 0;
  81
  82     if (buffer_left == 0)
  83     {
  84         lseek(fd, size_left, SEEK_CUR);     /* Skip everything */
  85     }
  86     else
  87     {
  88         /* Skip the data tag header - maybe we should parse it properly? */
  89         lseek(fd, 16, SEEK_CUR);
  90         size_left -= 16;
  91
  92         if (size_left > buffer_left)
  93         {
  94             read(fd, buffer, buffer_left);
  95             lseek(fd, size_left - buffer_left, SEEK_CUR);
  96             bytes_read = buffer_left;
  97         }
  98         else
  99         {
 100             read(fd, buffer, size_left);
 101             bytes_read = size_left;
 102         }
 103     }
 104
 105     return bytes_read;
 106 }
 107
 108 /* Read a string tag from an MP4 file */
 109 static unsigned int read_mp4_tag_string(int fd, int size_left, char** buffer,
 110                                         unsigned int* buffer_left, char** dest)
 111 {
 112     unsigned int bytes_read = read_mp4_tag(fd, size_left, *buffer,
 113         *buffer_left > 0 ? *buffer_left - 1 : 0);
 114     unsigned int length = 0;
 115
 116     if (bytes_read)
 117     {
 118         (*buffer)[bytes_read] = 0;
 119         *dest = *buffer;
 120         length = strlen(*buffer) + 1;
 121         *buffer_left -= length;
 122         *buffer += length;
 123     }
 124     else
 125     {
 126         *dest = NULL;
 127     }
 128
 129     return length;
 130 }
 131
 132 static unsigned int read_mp4_atom(int fd, uint32_t* size,
 133                                   uint32_t* type, uint32_t size_left)
 134 {
 135     read_uint32be(fd, size);
 136     read_uint32be(fd, type);
 137
 138     if (*size == 1)
 139     {
 140         /* FAT32 doesn't support files this big, so something seems to
 141          * be wrong. (64-bit sizes should only be used when required.)
 142          */
 143         errno = EFBIG;
 144         *type = 0;
 145         return 0;
 146     }
 147
 148     if (*size > 0)
 149     {
 150         if (*size > size_left)
 151         {
 152             size_left = 0;
 153         }
 154         else
 155         {
 156             size_left -= *size;
 157         }
 158
 159         *size -= 8;
 160     }
 161     else
 162     {
 163         *size = size_left;
 164         size_left = 0;
 165     }
 166
 167     return size_left;
 168 }
 169
 170 static unsigned int read_mp4_length(int fd, uint32_t* size)
 171 {
 172     unsigned int length = 0;
 173     int bytes = 0;
 174     unsigned char c;
 175
 176     do
 177     {
 178         read(fd, &c, 1);
 179         bytes++;
 180         (*size)--;
 181         length = (length << 7) | (c & 0x7F);
 182     }
 183     while ((c & 0x80) && (bytes < 4) && (*size > 0));
 184
 185     return length;
 186 }
 187
 188 static bool read_mp4_esds(int fd, struct mp3entry* id3, uint32_t* size)
 189 {
 190     unsigned char buf[8];
 191     bool sbr = false;
 192
 193     lseek(fd, 4, SEEK_CUR);     /* Version and flags. */
 194     read(fd, buf, 1);           /* Verify ES_DescrTag. */
 195     *size -= 5;
 196
 197     if (*buf == 3)
 198     {
 199         /* read length */
 200         if (read_mp4_length(fd, size) < 20)
 201         {
 202             return sbr;
 203         }
 204
 205         lseek(fd, 3, SEEK_CUR);
 206         *size -= 3;
 207     }
 208     else
 209     {
 210         lseek(fd, 2, SEEK_CUR);
 211         *size -= 2;
 212     }
 213
 214     read(fd, buf, 1);           /* Verify DecoderConfigDescrTab. */
 215     *size -= 1;
 216
 217     if (*buf != 4)
 218     {
 219         return sbr;
 220     }
 221
 222     if (read_mp4_length(fd, size) < 13)
 223     {
 224         return sbr;
 225     }
 226
 227     lseek(fd, 13, SEEK_CUR);    /* Skip audio type, bit rates, etc. */
 228     read(fd, buf, 1);
 229     *size -= 14;
 230
 231     if (*buf != 5)              /* Verify DecSpecificInfoTag. */
 232     {
 233         return sbr;
 234     }
 235
 236     {
 237         static const int sample_rates[] =
 238         {
 239             96000, 88200, 64000, 48000, 44100, 32000,
 240             24000, 22050, 16000, 12000, 11025, 8000
 241         };
 242         unsigned long bits;
 243         unsigned int length;
 244         unsigned int index;
 245         unsigned int type;
 246
 247         /* Read the (leading part of the) decoder config. */
 248         length = read_mp4_length(fd, size);
 249         length = MIN(length, *size);
 250         length = MIN(length, sizeof(buf));
 251         memset(buf, 0, sizeof(buf));
 252         read(fd, buf, length);
 253         *size -= length;
 254
 255         /* Maybe time to write a simple read_bits function... */
 256
 257         /* Decoder config format:
 258          * Object type           - 5 bits
 259          * Frequency index       - 4 bits
 260          * Channel configuration - 4 bits
 261          */
 262         bits = get_long_be(buf);
 263         type = bits >> 27;              /* Object type - 5 bits */
 264         index = (bits >> 23) & 0xf;     /* Frequency index - 4 bits */
 265
 266         if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 267         {
 268             id3->frequency = sample_rates[index];
 269         }
 270
 271         if (type == 5)
 272         {
 273             DEBUGF("MP4: SBR\n");
 274             unsigned int old_index = index;
 275
 276             sbr = true;
 277             index = (bits >> 15) & 0xf; /* Frequency index - 4 bits */
 278
 279             if (index == 15)
 280             {
 281                 /* 17 bits read so far... */
 282                 bits = get_long_be(&buf[2]);
 283                 id3->frequency = (bits >> 7) & 0x00ffffff;
 284             }
 285             else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
 286             {
 287                 id3->frequency = sample_rates[index];
 288             }
 289
 290             if (old_index == index)
 291             {
 292                 /* Downsampled SBR */
 293                 id3->frequency *= 2;
 294             }
 295         }
 296         /* Skip 13 bits from above, plus 3 bits, then read 11 bits */
 297         else if ((length >= 4) && (((bits >> 5) & 0x7ff) == 0x2b7))
 298         {
 299             /* extensionAudioObjectType */
 300             DEBUGF("MP4: extensionAudioType\n");
 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         }
 344     }
 345
 346     return sbr;
 347 }
 348
 349 static bool read_mp4_tags(int fd, struct mp3entry* id3,
 350                           uint32_t size_left)
 351 {
 352     uint32_t size;
 353     uint32_t type;
 354     unsigned int buffer_left = sizeof(id3->id3v2buf) + sizeof(id3->id3v1buf);
 355     char* buffer = id3->id3v2buf;
 356     bool cwrt = false;
 357
 358     do
 359     {
 360         size_left = read_mp4_atom(fd, &size, &type, size_left);
 361
 362         /* DEBUGF("Tag atom: '%c%c%c%c' (%d bytes left)\n", type >> 24 & 0xff,
 363             type >> 16 & 0xff, type >> 8 & 0xff, type & 0xff, size); */
 364
 365         switch (type)
 366         {
 367         case MP4_cnam:
 368             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 369                 &id3->title);
 370             break;
 371
 372         case MP4_cART:
 373             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 374                 &id3->artist);
 375             break;
 376
 377         case MP4_aART:
 378             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 379                 &id3->albumartist);
 380             break;
 381
 382         case MP4_cgrp:
 383             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 384                 &id3->grouping);
 385             break;
 386
 387         case MP4_calb:
 388             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 389                 &id3->album);
 390             break;
 391
 392         case MP4_cwrt:
 393             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 394                 &id3->composer);
 395             cwrt = false;
 396             break;
 397
 398         case MP4_ccmt:
 399             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 400                 &id3->comment);
 401             break;
 402
 403         case MP4_cday:
 404             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 405                                 &id3->year_string);
 406
 407             /* Try to parse it as a year, for the benefit of the database.
 408              */
 409             if(id3->year_string)
 410             {
 411                 id3->year = atoi(id3->year_string);
 412                 if (id3->year < 1900)
 413                 {
 414                     id3->year = 0;
 415                 }
 416             }
 417             else
 418                 id3->year = 0;
 419
 420             break;
 421
 422         case MP4_gnre:
 423             {
 424                 unsigned short genre;
 425
 426                 read_mp4_tag(fd, size, (char*) &genre, sizeof(genre));
 427                 id3->genre_string = id3_get_num_genre(betoh16(genre) - 1);
 428             }
 429             break;
 430
 431         case MP4_cgen:
 432             read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 433                 &id3->genre_string);
 434             break;
 435
 436         case MP4_disk:
 437             {
 438                 unsigned short n[2];
 439
 440                 read_mp4_tag(fd, size, (char*) &n, sizeof(n));
 441                 id3->discnum = betoh16(n[1]);
 442             }
 443             break;
 444
 445         case MP4_trkn:
 446             {
 447                 unsigned short n[2];
 448
 449                 read_mp4_tag(fd, size, (char*) &n, sizeof(n));
 450                 id3->tracknum = betoh16(n[1]);
 451             }
 452             break;
 453
 454         case MP4_extra:
 455             {
 456                 char tag_name[TAG_NAME_LENGTH];
 457                 uint32_t sub_size;
 458
 459                 /* "mean" atom */
 460                 read_uint32be(fd, &sub_size);
 461                 size -= sub_size;
 462                 lseek(fd, sub_size - 4, SEEK_CUR);
 463                 /* "name" atom */
 464                 read_uint32be(fd, &sub_size);
 465                 size -= sub_size;
 466                 lseek(fd, 8, SEEK_CUR);
 467                 sub_size -= 12;
 468
 469                 if (sub_size > sizeof(tag_name) - 1)
 470                 {
 471                     read(fd, tag_name, sizeof(tag_name) - 1);
 472                     lseek(fd, sub_size - (sizeof(tag_name) - 1), SEEK_CUR);
 473                     tag_name[sizeof(tag_name) - 1] = 0;
 474                 }
 475                 else
 476                 {
 477                     read(fd, tag_name, sub_size);
 478                     tag_name[sub_size] = 0;
 479                 }
 480
 481                 if ((strcasecmp(tag_name, "composer") == 0) && !cwrt)
 482                 {
 483                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 484                         &id3->composer);
 485                 }
 486                 else if (strcasecmp(tag_name, "iTunSMPB") == 0)
 487                 {
 488                     char value[TAG_VALUE_LENGTH];
 489                     char* value_p = value;
 490                     char* any;
 491                     unsigned int length = sizeof(value);
 492
 493                     read_mp4_tag_string(fd, size, &value_p, &length, &any);
 494                     id3->lead_trim = get_itunes_int32(value, 1);
 495                     id3->tail_trim = get_itunes_int32(value, 2);
 496                     DEBUGF("AAC: lead_trim %d, tail_trim %d\n",
 497                         id3->lead_trim, id3->tail_trim);
 498                 }
 499                 else if (strcasecmp(tag_name, "musicbrainz track id") == 0)
 500                 {
 501                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 502                         &id3->mb_track_id);
 503                 }
 504                 else if ((strcasecmp(tag_name, "album artist") == 0))
 505                 {
 506                     read_mp4_tag_string(fd, size, &buffer, &buffer_left,
 507                         &id3->albumartist);
 508                 }
 509                 else
 510                 {
 511                     char* any;
 512                     unsigned int length = read_mp4_tag_string(fd, size,
 513                         &buffer, &buffer_left, &any);
 514
 515                     if (length > 0)
 516                     {
 517                         /* Re-use the read buffer as the dest buffer... */
 518                         buffer -= length;
 519                         buffer_left += length;
 520
 521                         if (parse_replaygain(tag_name, buffer, id3,
 522                             buffer, buffer_left) > 0)
 523                         {
 524                             /* Data used, keep it. */
 525                             buffer += length;
 526                             buffer_left -= length;
 527                         }
 528                     }
 529                 }
 530             }
 531             break;
 532
 533         default:
 534             lseek(fd, size, SEEK_CUR);
 535             break;
 536         }
 537     }
 538     while ((size_left > 0) && (errno == 0));
 539
 540     return true;
 541 }
 542
 543 static bool read_mp4_container(int fd, struct mp3entry* id3,
 544                                uint32_t size_left)
 545 {
 546     uint32_t size;
 547     uint32_t type;
 548     uint32_t handler = 0;
 549     bool rc = true;
 550
 551     do
 552     {
 553         size_left = read_mp4_atom(fd, &size, &type, size_left);
 554
 555         /* DEBUGF("Atom: '%c%c%c%c' (0x%08x, %d bytes left)\n",
 556             (type >> 24) & 0xff, (type >> 16) & 0xff, (type >> 8) & 0xff,
 557             type & 0xff, type, size); */
 558
 559         switch (type)
 560         {
 561         case MP4_ftyp:
 562             {
 563                 uint32_t id;
 564
 565                 read_uint32be(fd, &id);
 566                 size -= 4;
 567
 568                 if ((id != MP4_M4A) && (id != MP4_M4B) && (id != MP4_mp42)
 569                     && (id != MP4_qt) && (id != MP4_3gp6))
 570                 {
 571                     DEBUGF("Unknown MP4 file type: '%c%c%c%c'\n",
 572                         (int)(id >> 24 & 0xff), (int)(id >> 16 & 0xff),
 573                         (int)(id >> 8 & 0xff), (int)(id & 0xff));
 574                     return false;
 575                 }
 576             }
 577             break;
 578
 579         case MP4_meta:
 580             lseek(fd, 4, SEEK_CUR);  /* Skip version */
 581             size -= 4;
 582             /* Fall through */
 583
 584         case MP4_moov:
 585         case MP4_udta:
 586         case MP4_mdia:
 587         case MP4_stbl:
 588         case MP4_trak:
 589             rc = read_mp4_container(fd, id3, size);
 590             size = 0;
 591             break;
 592
 593         case MP4_ilst:
 594             if (handler == MP4_mdir)
 595             {
 596                 rc = read_mp4_tags(fd, id3, size);
 597                 size = 0;
 598             }
 599             break;
 600
 601         case MP4_minf:
 602             if (handler == MP4_soun)
 603             {
 604                 rc = read_mp4_container(fd, id3, size);
 605                 size = 0;
 606             }
 607             break;
 608
 609         case MP4_stsd:
 610             lseek(fd, 8, SEEK_CUR);
 611             size -= 8;
 612             rc = read_mp4_container(fd, id3, size);
 613             size = 0;
 614             break;
 615
 616         case MP4_hdlr:
 617             lseek(fd, 8, SEEK_CUR);
 618             read_uint32be(fd, &handler);
 619             size -= 12;
 620             /* DEBUGF("    Handler '%c%c%c%c'\n", handler >> 24 & 0xff,
 621                 handler >> 16 & 0xff, handler >> 8 & 0xff,handler & 0xff); */
 622             break;
 623
 624         case MP4_stts:
 625             {
 626                 uint32_t entries;
 627                 unsigned int i;
 628
 629                 lseek(fd, 4, SEEK_CUR);
 630                 read_uint32be(fd, &entries);
 631                 id3->samples = 0;
 632
 633                 for (i = 0; i < entries; i++)
 634                 {
 635                     uint32_t n;
 636                     uint32_t l;
 637
 638                     read_uint32be(fd, &n);
 639                     read_uint32be(fd, &l);
 640                     id3->samples += n * l;
 641                 }
 642
 643                 size = 0;
 644             }
 645             break;
 646
 647         case MP4_mp4a:
 648         case MP4_alac:
 649             {
 650                 uint32_t frequency;
 651
 652                 id3->codectype = (type == MP4_mp4a) ? AFMT_MP4_AAC : AFMT_MP4_ALAC;
 653                 lseek(fd, 22, SEEK_CUR);
 654                 read_uint32be(fd, &frequency);
 655                 size -= 26;
 656                 id3->frequency = frequency;
 657
 658                 if (type == MP4_mp4a)
 659                 {
 660                     uint32_t subsize;
 661                     uint32_t subtype;
 662
 663                     /* Get frequency from the decoder info tag, if possible. */
 664                     lseek(fd, 2, SEEK_CUR);
 665                     /* The esds atom is a part of the mp4a atom, so ignore
 666                      * the returned size (it's already accounted for).
 667                      */
 668                     read_mp4_atom(fd, &subsize, &subtype, size);
 669                     size -= 10;
 670
 671                     if (subtype == MP4_esds)
 672                     {
 673                         read_mp4_esds(fd, id3, &size);
 674                     }
 675                 }
 676             }
 677             break;
 678
 679         case MP4_mdat:
 680             id3->filesize = size;
 681             break;
 682
 683         case MP4_chpl:
 684             {
 685                 /* ADDME: add support for real chapters. Right now it's only
 686                  * used for Nero's gapless hack */
 687                 uint8_t chapters;
 688                 uint64_t timestamp;
 689
 690                 lseek(fd, 8, SEEK_CUR);
 691                 read_uint8(fd, &chapters);
 692                 size -= 9;
 693
 694                 /* the first chapter will be used as the lead_trim */
 695                 if (chapters > 0) {
 696                     read_uint64be(fd, &timestamp);
 697                     id3->lead_trim = (timestamp * id3->frequency) / 10000000;
 698                     size -= 8;
 699                 }
 700             }
 701             break;
 702
 703         default:
 704             break;
 705         }
 706
 707         lseek(fd, size, SEEK_CUR);
 708     }
 709     while (rc && (size_left > 0) && (errno == 0) && (id3->filesize == 0));
 710     /* Break on non-zero filesize, since Rockbox currently doesn't support
 711      * metadata after the mdat atom (which sets the filesize field).
 712      */
 713
 714     return rc;
 715 }
 716
 717 bool get_mp4_metadata(int fd, struct mp3entry* id3)
 718 {
 719     id3->codectype = AFMT_UNKNOWN;
 720     id3->filesize = 0;
 721     errno = 0;
 722
 723     if (read_mp4_container(fd, id3, filesize(fd)) && (errno == 0)
 724         && (id3->samples > 0) && (id3->frequency > 0)
 725         && (id3->filesize > 0))
 726     {
 727         if (id3->codectype == AFMT_UNKNOWN)
 728         {
 729             logf("Not an ALAC or AAC file");
 730             return false;
 731         }
 732
 733         id3->length = ((int64_t) id3->samples * 1000) / id3->frequency;
 734
 735         if (id3->length <= 0)
 736         {
 737             logf("mp4 length invalid!");
 738             return false;
 739         }
 740
 741         id3->bitrate = ((int64_t) id3->filesize * 8) / id3->length;
 742         DEBUGF("MP4 bitrate %d, frequency %ld Hz, length %ld ms\n",
 743             id3->bitrate, id3->frequency, id3->length);
 744     }
 745     else
 746     {
 747         logf("MP4 metadata error");
 748         DEBUGF("MP4 metadata error. errno %d, frequency %ld, filesize %ld\n",
 749             errno, id3->frequency, id3->filesize);
 750         return false;
 751     }
 752
 753     return true;
 754 }