William Herrera
and 1 contributors


Audio::M4P::QuickTime -- Perl M4P/MP4/M4a audio / video tools


Perl manipulation of Quicktime Audio files, including protected audio M4P files. Allows extraction and modification of meta information in Apple QuickTime AAC/m4a music files.

About QuickTime File Structure and Atoms

M4P is a QuickTime protected audio file format. It is composed of a linear stream of bytes which are segmented into units called atoms. Some atoms may be containers for other atoms. iTunes Music Store M4P music files are Quicktime audio files which are encrypted using a combination of information in the file's drms atom and information which is commonly stored on the computer or audio player.


     use Audio::M4P::QuickTime;
     my $mp4file = "file.m4p";
     my $qt = new Audio::M4P::QuickTime(file => $mp4file);
     my $tags = $qt->GetMetaInfo;
     print "Artist is $tags->{ARTIST}\n" if $tags->{ARTIST};


Object Methods

 my $qt = Audio::M4P::QuickTime->new;

 $qt = new Audio::M4P::QuickTime(
   DEBUG => 2, 
   DEBUGDUMPFILE => 'quicktime_treedump.html'

 $qt = new Audio::M4P::QuickTime(file => 'qt_audio_file.m4p');

Create a new Audio::M4P::QuickTime object. DEBUG => 1 as argument causes parse and other information to be printed to stdout during processing. DEBUG => 2, DEBUGDUMPFILE => "file" causes an HTML tree representation of the QuickTime file to be emitted to the file given as value to the argument pair. file => "filename.m4p" causes the named QuickTime file to be read and parsed during object initialization.


Read the named file into the QuickTime object buffer.


Parse the file that has been read as a QuickTime stream.


Write the (possibly modified) file back to the output file argument.

 my $hashref = $qt->GetMetaInfo(1);
 while(my($tag, $value) = each %{$hashref}) { 
    print "$tag => $value\n";

Returns a hash reference to meta tag information. Attempts to be compatible with tag information formats in MP3::Info and MP4::Info. Potential tags are AAID, ALBUM, ARTIST, COMMENT, COM, CPIL, CPRT, YEAR, DISK, GENRE, GRP, NAM, RTNG, TMPO, TOO, TRKN, and WRT. Note that, due to preservation of compatibility with MP3::Info by returning tag info as a hash reference, duplicate entries of the same tag name, such as multiple comment fields, will not be returned in the hash reference. An optional second argument, if 1 or true, should convert some binary fields to text in the tags, for instance my $hashref = $qt->GetMetaInfo(1);

 my $hashref = $qt->GetMP4Info;
 while(my($tag, $value) = each %{$hashref}) { 
    print "$tag => $value\n";

Returns a hash reference to MP3 tag audio information. Attempts to be compatible with tag information formats in MP3::Info and MP4::Info. Potential tags are LAYER (1), VERSION (4), SIZE, SECONDS, SS, MM, and BITRATE.

 my $comment = "After paying for this music file, I have fair use rights to change it.";

 $qt->SetMetaInfo(COMMENT => $comment);
 $qt->SetMetaInfo(GENRE => "Bebop", 1, 'day');

Set a meta information field. The third argument, if given and true, indicates that the program should replace all instances of meta data of this type with the new entry, rather than adding the tag to the existing meta data. The fourth argument, if given and true, indicated a tag value before which the new tag is to be placed in the file. The fifth argument indicates the values are in text form, ie for meta type 'trkn', value is something like 'Track 5 of 11'.

 my $hashref = $qt->iTMS_MetaInfo;
 $hashref->{comments} = "A new comment";

Get or set a meta information field via a hash reference to an Apple iTMS type dict data structure. Possible fields are copyright, comments, songName, genre, playlistArtistName, genreID, composerName, playlistName, year, trackNumber, trackCount, discNumber, discCount, and artworkURL. iTMS meta data entries may not be compatible with MP3::Info type meta data. An optional second argument, if true, prevents the method from replacing old meta information, as in $qt->iTMS_MetaInfo($hashref, 1);

Note that although this method of manipulating M4P data tags is closest to the way iTMS and iTunes do metadata, it may be less intuitive for most audio tag programmers than the MP3::Tag and Audio::TagLib compatible methods below.

  my $artwork = $qt->GetCoverArt();
  foreach my $pic (@{$artwork}) { 
      # do stuff with art

Returns a reference to an array of cover artwork. Note: the artwork routines were suggested and largely contributed by pucklock. (Thanks!)

MP3::Tag and Audio::TagLib Compatible Functions

  my($title, $tracknum, $artist, $album, $comment, $year, $genre) =

Returns an array of tag metadata, similar to the same method in MP3::Tag.

  my $album = $qt->album;
  $new_album = "My New Album Name";

Get and set title tag data. Similar to the same method in MP3::TagLib.

Note this and other tag functions below will usually return the empty string "" when there is tag data lacking, unless an integer result is expected, in which case 0 is returned. This is for compatibility with MP3::Tag and Audio::TagLib's implementation of these methods.

  my $artist = $qt->artist;
  $new_artist = "My New Artist";

Get and set artist tag data. Similar to the same method in MP3::TagLib.

  my $comment = $qt->comment;
  $new_comment = "My Comment Goes Here";

Get and set comment tag data. Similar to the same method in MP3::Tag.

  my $genre = $qt->genre;
  $new_genre = 18;

Get and set genre tag data BY NUMBER.

  my $text_genre = $qt->genre_as_text;
  $new_genre = "Rock";

Get and set genre tag data as text. Note that the given text tag must exist in the genre database to work. See the "our @genre_strings" object in the code, which can be imported by the declaration "our @genre_strings;" in code using the module.

  my $title = $qt->title;
  $new_title = "My New One";

Get and set title tag data. Similar to the same method in MP3::Tag.

  my $track = $qt->track;
  my $new_track = 3;

Get or set the track number.

  my ($track, $count) = $qt->tracks;
  my $new_track_number = 3;
  my $total_tracks_on_CD = 17;
  $qt->tracks($new_track_number, $total_tracks_on_CD);

Get or set both the track number and the total tracks on the originating media work. Not actually an MP3::Tag method, but MP4 files, unlike many MP3 files, regularly contain both track number and the total originating CD's track count.

  my $total = $qt->total;
  my $new_total = 15;

Get or set the track total number.

  my $year = $qt->year;
  $new_year = "My New One";

Get and set year tag data. Similar to the same method in MP3::Tag.

  my $tref = $qt->all_tags( album => "My new album", genre => 21 );
  print $tref->{artist};

Similar to the Audio::File::Tag all method. Set or get all the above tags. To set the tags pass a hash reference with the names of the tags as keys and the tag values as hash values. Returns a hash reference if no argument is specified.

The following tag names are supported by this method: album artist comment genre ( the integer value genre ) title track total

Other Audio::TagLib syntactic compatibility

The following 'set' methods are equivalent to methods above used with an argument. They are included in this module for Audio::TagLib compatibility:
Method equivalent to
setAlbum album
setArtist artist
setTitle title
setComment comment
setGenre genre
setTrack track
setTracks tracks
setTotal total tracks

Apple m4a personal data removal function

  my $file_name = "mp4aIDfile.m4a";
  my $qt = Audio::M4P::QuickTime->new(file => $file_name);
  $qt->WriteFile('cleaned' . $file_name);



  use Tk;
  use Cwd;
  use strict;
  use warnings;
  use Audio::M4P::QuickTime;

  my $backup_requested = "yes";

  my $win = new MainWindow;
  my $frm = $win->Frame()->pack;
    -text => "Anonymize Apple iTunes Plus .m4a Files",
    -font => "Garamond 20 bold",

  my $do_backup_choice = $frm->Radiobutton(
    -text  => "Back Up (append .old.m4a to old files)",
    -value => 'yes',
    -variable => \$backup_requested,
    -font => "Garamond 14 bold",

  my $do_no_backup_choice = $frm->Radiobutton(
    -text     => "Do Not Back Up (files will be over-written!)",
    -value    => 'no',
    -variable => \$backup_requested,
    -font => "Garamond 14 bold",

  my $convert_button = $win->Button(
    -text    => "Convert Files",
    -command => \&push_button,
    -font => "Garamond 17 bold",

  my $exit_button = $win->Button(
    -text    => "Exit",
    -command => sub { exit 0 },
    -font => "Garamond 17 bold",


  sub push_button {
    my $write_extension = $backup_requested eq 'no' ? '' : '.old.m4a';
    my @file_list = $win->getOpenFile(
        -defaultextension => ".pl",
        -filetypes        => [ [ 'MP4a files', '.m4a', ], [ 'All Files', '*', ], ],
        -initialdir       => Cwd::cwd(),
        -initialfile      => "getopenfile",
        -title    => "Choose Purchased Apple iTunes Plus Files to Anonymize",
        -multiple => 1,

    foreach my $filename (@file_list) {
        my $qt = Audio::M4P::QuickTime->new( file => $filename );
        if ( $qt->FindAtom("mp4a") ) {
            rename( $filename, $filename . $write_extension );
        else {
                -message => "Error: $filename is not a valid m4a file.",
                -type    => 'ok',
                -icon    => 'error'

Remove personal identifiers from Apple's iTMS .m4a format files.

  Note: to prevent inadvertent alteration of non-Apple .m4a files, the function
  requires a m4a atom to be part of the file unless the "force" argument is used, eg.

  $qt->CleanAppleM4aPersonalData( force => 1, zero_free_atoms => 1 );
  Here, the zero_free_atoms => 1 named argument forces all data in free atoms 
  to be nulled out as well.

Class Internal Methods and Functions



    The Audio::M4P::* code is not re-entrant on a per-file basis, due to recursive changes to containers not being thread-safe. Threaded code using these modules may need to lock down all method calls with a semaphore or other serialization method, unless only one thread is used to modify any given audio file.


Audio::M4P, Audio::M4P::Atom


LWP::UserAgent::iTMS_Client, iTunes::Sid
MP3::Info, MP4::Info, MP3::Tag, Audio::TagLib, Audio::File::Tag, Mac::iTunes, Net::iTMS, LWP::UserAgent::iTMS_Client


    William Herrera wherrera@skylightview.com.


    Questions, feature requests and bug reports should go to <wherrera@skylightview.com>.


    Copyright (c) 2003-2008 William Herrera. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.