brian d foy > Mac-iTunes-1.22 > iTunes

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NAME ^

iTunes Music Library File Format

SYNOPSIS ^

This file describes the iTunes Music Library file format for application versions 1.1.2 and 3.0.

DESCRIPTION ^

The iTunes Music Library file contains a series of variable length blocks. The first part of the file refers to iTunes in general and to the number of playlists the file contains. The middle part holds all of the MP3 data, which is only stored once per item. Each item has a unique identifier used later in the file. The last part of the file contains a list of playlists, and within each playlist is a list of the item identifiers from the middle of the file.

Markers

Each block of data begins with a four letter marker which denotes the type of block. Some blocks contain sub-blocks, which means you cannot simply read to the next marker.

The blocks show up roughly in this order:

hdfm -- file header
hdsm -- part header ?
htlm -- master items list header ?
htim -- master item record
hohm -- data sublock, multi-purpose (in htim, hpim blocks)
hplm -- playlist list header ?
hpim -- start of playlist block
hptm -- item indentifier sub-block for hpim

Block format

hdfm
    Byte   Length  Comment
    -----------------------
      0       4     'hdfm'
      4       4     L = header length
      8       4     file length ?
     12       4     ?
     13       1     N = length of version string
     14       N     application version string
     14+N   L-N-17  ?
hdsm
    Byte   Length  Comment
    -----------------------
      0       4     'hdsm'
      4       4     L = header length
      8       4     ?
     12       4     block type ?
     16      L-16   ?
htlm
    Byte   Length  Comment
    -----------------------
      0       4     'htlm'
      4       4     L = header length
      8       4     number of songs
     12      L-12   ?
htim
    Byte   Length  Comment
    -----------------------
      0       4     'htim'
      4       4     L = header length (usually 156, or 0x9C)
      8       4     R = total record length, including sub-blocks
     12       4     N = number of hohm sub-blocks
     16       4     song identifier
     20       4     block type => (1, ?)
     24       4     ?
     28       4     Mac OS file type (e.g. MPG3)
     32       4     modification date
     36       4     file size, in bytes
     40       4     playtime, millisecs
     44       4     track number
     48       4     total number of tracks
     52       2     ?
     54       2     year
     56       2     ?
     58       2     bit rate
     60       2     sample rate
     62       2     ?
     64       4     volume adjustment (signed)
     68       4     start time, milliseconds
     72       4     end time, milliseconds
     76       4     playcount
     80       2     ?
     82       2     compilation (1 = yes, 0 = no)
     84      12     ?
     96       4     playcount again?
    100       4     last play date
    104       2     disk number
    106       2     total disks
    108       1     rating ( 0 to 100 )
    109      11     ?
    120       4     add date
    124      32     ?
    156      R-L    hohm sub blocks
hohm

The hohm block has a header, annotated immediately below, and a data-specific block.

    Byte   Length  Comment
    -----------------------
      0       4     'hohm'
      4       4     L = header length, usually 0x18
      8       4     R = total record length
     12       4     block type, (1, 2, 3, 4, 5, 6, 0x0b, 0x64)
     16      12     ?
     28     R-28    block specific data
hohm block types

The data-specific structure follows the header structure of the hohm block. Offsets start at 0', which is byte 28 in the record. Sometimes these data appear to have null bytes alternate with information bytes, as in the Perl string "\000H\000e\000l\000l\000o". In that case, the null bytes count in the length of the data.

    Type  Decimal   Description
    --------------------------------------
     1              big bag of gook     
     2              song title
     3              album title
     4              artist name
     5              genre string (not number)
     6              file type (e.g. MPEG)
     8              comments
     b      11      URL
     c      12      composer
    3a      58      equalizer data?
    3c      60      equalizer preset (text)
    64     100      playlist name (used in hpim)
hohm type 1
    Byte   Length  Comment
    -----------------------
      0'      2     ?
      2       2     n = length of next thingy ?
      4       n     ?
      4+n     1     N = volume name length up to 27 (e.g. hard drive name)
      5+n     N     volume name
             27-N   left over bytes from volume name (null bytes)
              2     ?? (iTunes 3)
      5+n+N   1     M = filename length
      6+n+N   M     filename

      (let A = n+N+M )

       6+A    4     Mac OS file type
      10+A    4     Mac OS creator
      14+A   20     ?
      24+A    4     B = directory name length
      28+A    B     directory name
      28+A+B  C?    ? gook up to the sequence 0x5a_00_02_00 ? (iTunes 1)
                    ? gook up to the sequence 0x7f_00_02_00 ? (iTunes 3)

      (let A' = A+B+C )

      28+A'   2     D = length of fully qualified path
      30+A'   D    path

 =item hohm type 11 (0x0b)

    Byte   Length  Comment
    -----------------------
      0'     12      ?
     12       4      N = length of data
     16       8      ?
     24       N      URL
hohm type 100 (0x64)
    Byte   Length  Comment
    -----------------------
      0'     12      ?
     12       4      N = length of playlist name
     16       8      ?
     24       N      playlist name
other hohm types
    Byte   Length  Comment
    -----------------------
      0'     12      ?
     12       4      N = length of data
     16       8      ?
     24       N      data
hpim
    Byte   Length  Comment
    -----------------------
      0       4      hpim
      4       4      N = length of data
      8       4      ?
     12       4      ?
     16       4      number of items (hptm) in playlist
hptm
    Byte   Length  Comment
    -----------------------
      0       4      hpim
      4       4      N = length of data
      8      16      ?
     24       4      song key (from htim)
     28     N - 28   ?

TO DO ^

* verify that this works on all available versions

BUGS ^

* i've guessed on almost everything in this document, but it seems to work.

AUTHOR ^

Copyright 2002, brian d foy <bdfoy@cpan.org>

You may redistribute this under the same terms as Perl.

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