Add ReplayGain information to id3 tags of mp3 files

replaygain-id3

#!/usr/bin/env perl

use strict;
use warnings;
use File::Which;
use Getopt::Long qw(:config auto_help);
use Pod::Usage;
use String::ShellQuote;

my $VERSION = '0.01';

GetOptions(
    'a|album'   => \my $album_mode,
    'v|version' => sub { print "replaygain-id3 $VERSION\n"; exit },
) or pod2usage();

die "mp3gain not installed\n" if !defined which('mp3gain');
die "eyeD3 not installed\n" if !defined which('eyeD3');

@ARGV = grep { /\.mp3$/i } @ARGV;
die "No mp3 files specified\n" if !@ARGV;
my $files = shell_quote(@ARGV);

# calculate ReplayGain data with mp3gain(1)
my @tracks_raw = split /\n\n/, qx{mp3gain -s s $files};
my $album_raw = splice @tracks_raw, -1;
my %album;
$album{gain} = sprintf('%.2f dB', $album_raw =~ /^Recommended "Album" dB change for all files: (.+)$/m);

for my $track_raw (@tracks_raw) {
    my %track;
    my ($file) = $track_raw =~ /\A(.+)\n/m;
    next if $file !~ /\.mp3$/i;
    
    ($track{gain}) = $track_raw =~ /^Recommended "Track" dB change: (.+)$/m;
    $track{gain} = sprintf('%.2f dB', $track{gain});
    
    ($track{peak}) = $track_raw =~ /^Max PCM sample at current gain: (.+)$/m;
    $album{peak} = $track{peak} if !defined $album{peak} || $track{peak} > $album{peak};
    $track{peak} = sprintf('%.6f', $track{peak} / 32768);
    
    $album{tracks}{$file} = \%track;
}
$album{peak} = sprintf('%.6f', $album{peak} / 32768);

# tag the files with eyeD3(1)
while (my ($file, $track) = each %{ $album{tracks} }) {
    my @frames = (
        "replaygain_track_gain:$track->{gain}",
        "replaygain_track_peak:$track->{peak}",
        ($album_mode
            ? ("replaygain_album_gain:$album{gain}",
              "replaygain_album_peak:$album{peak}")
            : ()
        )
    );
    system "eyeD3 ".join(' ', map({ "--set-user-text-frame='$_'" } @frames)).' '.shell_quote($file)." >/dev/null 2>&1";
}

=head1 NAME

replaygain-id3 - Add ReplayGain information to id3 tags of mp3 files

=head1 SYNOPSIS

B<replaygain-id3> [options] <files>

 Options:
   -a, --album      Enable album mode (see below)
   -h, --help       Print this help message
   -v, --version    Print version

If you enable album mode, the affected files will be considered to be part
of the same album, and the corresponding album-global ReplayGain info will
be added.

Examples:

 # an album
 replaygain-id3 -a My_artist-My_album/*
 
 # unsorted mp3 files
 replaygain-id3 misc_mp3/*

=head1 DESCRIPTION

This little script uses C<mp3gain> to calculate ReplayGain information for
mp3 files specified on the command line. It will then add that information
to id3 v2 tags in the files using the C<eyeD3> program.

=head1 AUTHOR

Hinrik E<Ouml>rn SigurE<eth>sson, hinrik.sig@gmail.com

=head1 LICENSE AND COPYRIGHT

Copyright 2009 Hinrik E<Ouml>rn SigurE<eth>sson

This program is free software, you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut