Thomas Geffert > tagged-0.40 > MP3::Tag::ID3v2

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Module Version: 0.40   Source  

NAME ^

MP3::Tag::ID3v2 - Read / Write ID3v2.3 tags from mp3 audio files

SYNOPSIS ^

MP3::Tag::ID3v2 is designed to be called from the MP3::Tag module.

  use MP3::Tag;
  $mp3 = MP3::Tag->new($filename);

  # read an existing tag
  $mp3->get_tags();
  $id3v2 = $mp3->{ID3v2} if exists $mp3->{ID3v2};

  # or create a new tag
  $id3v2 = $mp3->new_tag("ID3v2");

See MP3::Tag for information on the above used functions.

* Reading a tag

  $frameIDs_hash = $id3v2->get_frame_ids;

  foreach my $frame (keys %$frameIDs_hash) {
      my ($info, $name) = $id3v2->get_frame($frame);
      if (ref $info) {
          print "$name ($frame):\n";
          while(my ($key,$val)=each %$info) {
              print " * $key => $val\n";
          }
      } else {
          print "$name: $info\n";
      }
  }

* Adding / Changing / Removing / Writing a tag

  $id3v2->add_frame("TIT2", "Title of the song");
  $id3v2->change_frame("TALB","Greatest Album");
  $id3v2->remove_frame("TLAN");
  $id3v2->write_tag();

* Removing the whole tag

  $id3v2->remove_tag();

* Get information about supported frames

  %tags = $id3v2->supported_frames();
  while (($fname, $longname) = each %tags) {
      print "$fname $longname: ", 
            join(", ", @{$id3v2->what_data($fname)}), "\n";
  }

AUTHOR ^

Thomas Geffert, thg@users.sourceforge.net

DESCRIPTION ^

get_frame_ids()

  $frameIDs = $tag->get_frame_ids;

  [old name: getFrameIDs() . The old name is still available, but you should use the new name]

get_frame_ids loops through all frames, which exist in the tag. It returns a hash reference with a list of all available Frame IDs. The keys of the returned hash are 4-character-codes (short names), the internal names of the frames, the according value is the english (long) name of the frame.

You can use this list to iterate over all frames to get their data, or to check if a specific frame is included in the tag.

If there are multiple occurences of a frame in one tag, the first frame is returned with its normal short name, following frames of this type get a '00', '01', '02', ... appended to this name. These names can then used with get_frame to get the information of these frames.

get_frame()

  ($info, $name) = get_frame($ID);
  ($info, $name) = get_frame($ID, 'raw');

  [old name: getFrame() . The old name is still available, but you should use the new name]

get_frame gets the contents of a specific frame, which must be specified by the 4-character-ID (aka short name). You can use get_frame_ids to get the IDs of the tag, or use IDs which you hope to find in the tag. If the ID is not found, get_frame returns (undef, undef).

Otherwise it extracts the contents of the frame. Frames in ID3v2 tags can be very small, or complex and huge. That is the reason, that get_frame returns the frame data in two ways, depending on the tag.

If it is a simple tag, with only one piece of data, this date is returned directly as ($info, $name), where $info is the text string, and $name is the long (english) name of the frame.

If the frame consist of different pieces of data, $info is a hash reference, $name is again the long name of the frame.

The hash, to which $info points, contains key/value pairs, where the key is always the name of the data, and the value is the data itself.

If the name starts with a underscore (as eg '_code'), the data is probably binary data and not printable. If the name starts without an underscore, it should be a text string and printable.

If there exists a second parameter like raw, the whole frame data is returned, but not the frame header. If the data was stored compressed, it is also in raw mode uncompressed before it is returned. Then $info contains a string with all data (which might be binary), and $name against the long frame name.

See also MP3::Tag::ID3v2-Data for a list of all supported frames, and some other explanations of the returned data structure.

! Encrypted frames are not supported yet !

! Some frames are not supported yet, but the most common ones are supported !

write_tag()

  $id3v2->write_tag;

Saves all frames to the file. It tries to update the file in place, when the space of the old tag is big enough for the new tag. Otherwise it creates a temp file with a new tag (i.e. copies the whole mp3 file) and renames/moves it to the original file name.

An extended header with CRC checksum is not supported yet.

At the moment the tag is automatically unsynchronized.

remove_tag()

  $id3v2->remove_tag();

Removes the whole tag from the file by copying the whole mp3-file to a temp-file and renaming/moving that to the original filename.

add_frame()

  $fn = $id3v2->add_frame($fname, @data);

Add a new frame, identified by the short name $fname. The $data must consist from so much elements, as described in the ID3v2.3 standard. If there is need to give an encoding parameter and you would like standard ascii encoding, you can omit the parameter or set it to 0. Any other encoding is not supported yet, and thus ignored.

It returns the the short name $fn, which can differ from $fname, when there existed already such a frame. If no other frame of this kind is allowed, an empty string is returned. Otherwise the name of the newly created frame is returned (which can have a 01 or 02 or ... appended).

@data must be undef or the number of elements of @data must be equal to the number of fields of the tag. See also MP3::Tag::ID3v2-Data.

You have to call write_tag() to save the changes to the file.

Examples:

 $f = add_frame("TIT2", 0, "Abba");   # $f="TIT2"  
 $f = add_frame("TIT2", "Abba");      # $f="TIT201", encoding=0 implicit

 $f = add_frame("COMM", "ENG", "Short text", "This is a comment");

 $f = add_frame("COMM");              # creates an empty frame

 $f = add_frame("COMM", "ENG");       # ! wrong ! $f=undef, becaues number 
                                      # of arguments is wrong

change_frame()

  $id3v2->change_frame($fname, @data);

Change an existing frame, which is identified by its short name $fname. @data must be same as in add_frame;

If the frame $fname doesn't exist, undef is returned.

You have to call write_tag() to save the changes to the file.

remove_frame()

  $id3v2->remove_frame($fname);

Remove an existing frame. $fname is the short name of a frame, eg as returned by get_frame_ids.

You have to call write_tag() to save the changes to the file.

supported_frames()

  $frames = $id3v2->supported_frames();

Returns a hash reference with all supported frames. The keys of the hash are the short names of the supported frames, the according values are the long (english) names of the frames.

what_data()

  ($data, $res_inp) = $id3v2->what_data($fname);

Returns an array reference with the needed data fields for a given frame. At this moment only the internal field names are returned, without any additional information about the data format of this field. Names beginning with an underscore (normally '_data') can contain binary data.

$resp_inp is a reference to an array, which contains information about a restriction for the content of the data field ( coresspodending to the same array field in the @$data array). If the entry is undef, no restriction exists. Otherwise it is a hash. The keys of the hash are the allowed input, the correspodending value is the value which should stored later in that field. If the value is undef then the key itself is valid for saving. If the hash contains an entry with "_FREE", the hash contains only suggestions for the input, but other input is also allowed.

Example for picture types of the APIC frame:

{"Other" = "\x00", "32x32 pixels 'file icon' (PNG only)" => "\x01", "Other file icon" => "\x02", ...}>

song()

Returns the song title (TIT2) from the tag.

track()

Returns the track number (TRCK) from the tag.

artist()

Returns the artist name (TPE1 (or TPE2 if TPE1 does not exist)) from the tag.

album()

Returns the album name (TALB) form the tag.

new()

  $tag = new($mp3fileobj);

new() needs as parameter a mp3fileobj, as created by MP3::Tag::File. new tries to find a ID3v2 tag in the mp3fileobj. If it does not find a tag it returns undef. Otherwise it reads the tag header, as well as an extended header, if available. It reads the rest of the tag in a buffer, does unsynchronizing if neccessary, and returns a ID3v2-object. At this moment only ID3v2.3 is supported. Any extended header with CRC data is ignored, so no CRC check is done at the moment. The ID3v2-object can be used to extract information from the tag.

Please use

   $mp3 = MP3::Tag->new($filename);
   $mp3->get_tags();                 ## to find an existing tag, or
   $id3v2 = $mp3->new_tag("ID3v2");  ## to create a new tag

instead of using this function directly

SEE ALSO ^

MP3::Tag, MP3::Tag::ID3v1, MP3::Tag::ID3v2-Data

ID3v2 standard - http://www.id3.org

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