Friday, April 30, 1999

***WARNING***

This module seems quite stable, and my tests (more extensive now)
seem to work well, and the reports I've gotten are positive.
There have been significant changes to the most important functions,
which should improve performance and reliability.  These should
make the module better, but may in some cases make it worse
for your MP3 files.

If you are having problems with an MP3 file and this module, please
contact me directly.  I will likely ask you to put the MP3 file(s)
in question in a place I can access them (HTTP or FTP), so I can test
them directly (NOTE: this is not just a clever ploy to get you to
send me MP3s :).

I don't anticipate serious problems, and in fact I have not been able
to find an MP3 file that the new module fails on.  But you have been
warned.

***WARNING***

This archive can always be obtained from:

    http://www.perl.com/CPAN/authors/id/CNANDOR/
    http://www.perl.com/CPAN/modules/by-module/MPEG/

Mac users: The file is a tarred, gzipped file.  Use Stuffit Expander 
or a similar program (like my cpan-mac stuff, also in the CNANDOR
directory) to get at the archive.

Please let me know how well it does(n't) work, and any changes you'd 
like to see.

Check out the script from Meng Weng Wong in eg/, it's pretty cool, and
if you have the CDDB module, it will be even cooler.  There's
also a MacPerl script for editing tags (mp3tag) in there.

#============================================================================

NAME
    MPEG::MP3Info - Manipulate / fetch info from MP3 audio files

SYNOPSIS
        #!perl -w
        use MPEG::MP3Info;
        my $file = 'Pearls_Before_Swine.mp3';
        set_mp3tag($file, 'Pearls Before Swine', q"77's",
          'Sticks and Stones', '1990', q"(c) 1990 77's LTD.", 'rock & roll');

        my $tag = get_mp3tag($file) or die "No TAG info";
        $tag->{GENRE} = 'rock';
        set_mp3tag($file, $tag);

        my $info = get_mp3info($file);
        printf "$file length is %d:%d", $info->{MM}, $info->{SS};

DESCRIPTION
    use_winamp_genres()
    Puts WinAmp genres into `@mp3_genres' and `%mp3_genres'.

    You can import the data structures with one of:

        use MPEG::MP3Info qw(:genres);
        use MPEG::MP3Info qw(:DEFAULT :genres);
        use MPEG::MP3Info qw(:all);

    remove_mp3tag (FILE)
    Removes last 128 bytes from file if those last 128 bytes begin with
    the text `TAG'. File will be 128 bytes shorter. Returns undef if no
    existing TAG found, 1 on successful removal of TAG.

    set_mp3tag (FILE, TITLE, ARTIST, ALBUM, YEAR, COMMENT, GENRE [, TRACKNUM])
    set_mp3tag (FILE, $HASHREF)
    Adds/changes tag information in an MP3 audio file. Will clobber any
    existing information in file.

    Fields are TITLE, ARTIST, ALBUM, YEAR, COMMENT, GENRE. All fields have
    a 30-byte limit, except for YEAR, which has a four-byte limit, and
    GENRE, which is one byte in the file. The GENRE passed in the function
    is a case-insensitive text string representing a genre found in
    `@mp3_genres'.

    Will accept either a list of values, or a hashref of the type returned
    by `get_mp3tag'.

    If TRACKNUM is present (for ID3v1.1), then the COMMENT field can only
    be 28 bytes.

    get_mp3tag (FILE)
    Returns hash reference containing tag information in MP3 file. Same
    info as described in `set_mp3tag'.

    get_mp3info (FILE)
    Returns hash reference containing file information for MP3 file. This
    data cannot be changed. Returned data includes MP3 version (VERSION),
    total time in minutes (MM) and seconds (SS), boolean for stereo
    (STEREO), MPEG layer (LAYER), BITRATE, and FREQUENCY.

TODO
    ID3v2 Support
        Added recognition of ID3v2 headers, speeding up `get_mp3info' for
        those files that have ID3v2 tags. Want to add functionality to get
        and set data in those tags. Too busy to do it. If someone wants to
        patch the module, feel free to submit patches.

    Variable Bitrate MP3s
        Get correct length in MM:SS ... anything other problems relating
        to this? Need algorithm for it.

HISTORY
    v0.63, Friday, April 30, 1999
        Added ID3v1.1 support. Thanks Trond Michelsen <mike@crusaders.no>,
        Pass F. B. Travis <pftravis@bellsouth.net>.

        Added 255 (\xFF) as default genre. Thanks Andrew Phillips
        <asp@wasteland.org>.

        I think I fixed bug relating to spaces in ID3v2 headers. Thanks
        Tom Brown.

    v0.62, Sunday, March 7, 1999
        Doc updates.

        Fix small unnoticable bug where ID3v2 offset is tag size plus 10,
        not just tag size.

        Not publickly released.

    v0.61, Monday, March 1, 1999
        Fixed problem of not removing nulls on return from `get_mp3tag'
        (was using spaces for padding before ... now trailing whitespace
        and all nulls are removed before returning tag info).

        Made tests more extensive (more for my own sanity when making all
        these changes than to make sure it works on other platforms and
        machines :).

    v0.60, Sunday, February 28, 1999
        Cleaned up a lot of stuff, added more comments, made `get_mp3info'
        much faster and much more reliable, and added recognition of ID3v2
        headers. Thanks to Tom Brown <thecap@usa.net> for his help.

        See for more info on ID3v2:

            http://www.id3.org/

    v0.52, Sunday, February 21, 1999
        Fixed problem in `get_mp3tag' that changed value of `$_' in caller
        (Todd Hanneken <thanneken@hds.harvard.edu>).

    v0.51, Saturday, February 20, 1999
        Fixed problem with `%winamp_genres' having the wrong numbers
        (Matthew Sachs).

    v0.50, Friday, February 19, 1999
        Added `remove_mp3tag'. Addeed VERSION to the hash returned by
        `get_mp3info', and fixed a bug where STEREO was not being set
        correctly.

        Export all genre data structures on request. Added
        `use_winamp_genres' to use WinAmp genres (Roland Steinbach
        <roland@support-system.com>).

        Added a `$MPEG::MP3Info::try_harder' variable that will try harder
        to find the MP3 header in a file. False by default. Can take a
        long time to fail, but should find most headers at any offets if
        set to true.

        Thanks to Matthew Sachs for his input and fixes.

            mailto:matthewg@interport.net
            http://www.zevils.com/linux/mp3tools/

        Thanks also to Peter Kovacs <kovacsp@egr.uri.edu>.

    v0.20, Saturday, October 17, 1998
        Changed name from `MPEG::MP3Tag' to `MPEG::MP3Info', because it
        does more than just TAG stuff now.

        Made header stuff even more reliable. Lots of help and testing
        from Meng Weng Wong again. :-)

    v0.13, Thursday, October 8, 1998
        Had some problems with header verification, got some code from
        Predrag Supurovic:

            mailto:mpgtools@dv.co.yu
            http://www.dv.co.yu/mp3list/mpgtools.htm
            http://www.dv.co.yu/mp3list/mpeghdr.htm

        Great stuff. Also did some looping to find a header if it is not
        in the "right" place. I did what I think it is a smart way to do
        it, since some files have the header as far down as 2 kbytes into
        the file. First, I look at position 0, then at position 36 (a
        position where I have found many headers), then I start at 0 again
        and jump in 128-byte chunks. Once I do that a bunch of times, I go
        back at the beginning and try at 0 and go ahead in 1-byte chunks
        for a bunch more times.

        If you have an MP3 that has the header begin at an odd place like
        byte 761, then I suggest you strip out the junk before the header
        begins. :-)

    v0.12, Friday, October 2, 1998
        Added `get_mp3info'. Thanks again to mp3tool source from Johann
        Lindvall, because I basically stole it straight (after converting
        it from C to Perl, of course).

        I did everything I could to find the header info, but if anyone
        has valid MP3 files that are not recognized, or has suggestions
        for improvement of the algorithms, let me know.

    v0.04, Tuesday, September 29, 1998
        Changed a few things, replaced a regex with an `unpack' (Meng Weng
        Wong <mengwong@pobox.com>).

    v0.03, Tuesday, September 8, 1998
        First public release.

AUTHOR AND COPYRIGHT
    Chris Nandor <pudge@pobox.com>, http://pudge.net/

    Copyright (c) 1999 Chris Nandor. All rights reserved. This program is
    free software; you can redistribute it and/or modify it under the
    terms of the Artistic License, distributed with Perl.

    Thanks to Johann Lindvall for his mp3tool program:

        http://www.dtek.chalmers.se/~d2linjo/mp3/mp3tool.html

    Helped me figure it all out.

VERSION
    v0.63, Friday, April 30, 1999

#============================================================================
