File Coverage

blib/lib/MP3/Info.pm

Criterion	Covered	Total	%
statement	322	481	66.9
branch	141	294	47.9
condition	43	120	35.8
subroutine	22	30	73.3
pod	7	8	87.5
total	535	933	57.3

package MP3::Info;
require 5.006;
use overload;
use strict;
use Carp;

use vars qw(
	@ISA @EXPORT @EXPORT_OK %EXPORT_TAGS $VERSION $REVISION
	@mp3_genres %mp3_genres @winamp_genres %winamp_genres $try_harder
	@t_bitrate @t_sampling_freq @frequency_tbl %v1_tag_fields
	@v1_tag_names %v2_tag_names %v2_to_v1_names $AUTOLOAD
	@mp3_info_fields
);

@ISA = 'Exporter';
@EXPORT = qw(
	set_mp3tag get_mp3tag get_mp3info remove_mp3tag
	use_winamp_genres
);
@EXPORT_OK = qw(@mp3_genres %mp3_genres use_mp3_utf8);
%EXPORT_TAGS = (
	genres	=> [qw(@mp3_genres %mp3_genres)],
	utf8	=> [qw(use_mp3_utf8)],
	all	=> [@EXPORT, @EXPORT_OK]
);

# $Id: Info.pm,v 1.19 2005/03/11 04:41:29 pudge Exp $
($REVISION) = ' $Revision: 1.19 $ ' =~ /\$Revision:\s+([^\s]+)/;
$VERSION = '1.13';

=pod

=head1 NAME

MP3::Info - Manipulate / fetch info from MP3 audio files

=head1 SYNOPSIS

	#!perl -w
	use MP3::Info;
	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\n", $info->{MM}, $info->{SS};

=cut

{
	my $c = -1;
	# set all lower-case and regular-cased versions of genres as keys
	# with index as value of each key
	%mp3_genres = map {($_, ++$c, lc, $c)} @mp3_genres;

	# do it again for winamp genres
	$c = -1;
	%winamp_genres = map {($_, ++$c, lc, $c)} @winamp_genres;
}

=pod

	my $mp3 = new MP3::Info $file;
	$mp3->title('Perls Before Swine');
	printf "$file length is %s, title is %s\n",
		$mp3->time, $mp3->title;


=head1 DESCRIPTION

=over 4

=item $mp3 = MP3::Info-Enew(FILE)

OOP interface to the rest of the module.  The same keys
available via get_mp3info and get_mp3tag are available
via the returned object (using upper case or lower case;
but note that all-caps "VERSION" will return the module
version, not the MP3 version).

Passing a value to one of the methods will set the value
for that tag in the MP3 file, if applicable.

=cut

sub new {
	my($pack, $file) = @_;

	my $info = get_mp3info($file) or return undef;
	my $tags = get_mp3tag($file) || { map { ($_ => undef) } @v1_tag_names };
	my %self = (
		FILE		=> $file,
		TRY_HARDER	=> 0
	);

	@self{@mp3_info_fields, @v1_tag_names, 'file'} = (
		@{$info}{@mp3_info_fields},
		@{$tags}{@v1_tag_names},
		$file
	);

	return bless \%self, $pack;
}

sub can {
	my $self = shift;
	return $self->SUPER::can(@_) unless ref $self;
	my $name = uc shift;
	return sub { $self->$name(@_) } if exists $self->{$name};
	return undef;
}

sub AUTOLOAD {
	my($self) = @_;
	(my $name = uc $AUTOLOAD) =~ s/^.*://;

	if (exists $self->{$name}) {
		my $sub = exists $v1_tag_fields{$name}
			? sub {
				if (defined $_[1]) {
					$_[0]->{$name} = $_[1];
					set_mp3tag($_[0]->{FILE}, $_[0]);
				}
				return $_[0]->{$name};
			}
			: sub {
				return $_[0]->{$name}
			};

		no strict 'refs';
		*{$AUTOLOAD} = $sub;
		goto &$AUTOLOAD;

	} else {
		carp(sprintf "No method '$name' available in package %s.",
			__PACKAGE__);
	}
}

sub DESTROY {

}


=item use_mp3_utf8([STATUS])

Tells MP3::Info to (or not) return TAG info in UTF-8.
TRUE is 1, FALSE is 0.  Default is TRUE, if available.

Will only be able to turn it on if Encode is available.  ID3v2
tags will be converted to UTF-8 according to the encoding specified
in each tag; ID3v1 tags will be assumed Latin-1 and converted
to UTF-8.

Function returns status (TRUE/FALSE).  If no argument is supplied,
or an unaccepted argument is supplied, function merely returns status.

This function is not exported by default, but may be exported
with the C<:utf8> or C<:all> export tag.

=cut

my $unicode_module = eval { require Encode; require Encode::Guess };
my $UNICODE = use_mp3_utf8($unicode_module ? 1 : 0);

sub use_mp3_utf8 {
	my($val) = @_;
	if ($val == 1) {
		if ($unicode_module) {
			$UNICODE = 1;
			$Encode::Guess::NoUTFAutoGuess = 1;
		}
	} elsif ($val == 0) {
		$UNICODE = 0;
	}
	return $UNICODE;
}

=pod

=item use_winamp_genres()

Puts WinAmp genres into C<@mp3_genres> and C<%mp3_genres>
(adds 68 additional genres to the default list of 80).
This is a separate function because these are non-standard
genres, but they are included because they are widely used.

You can import the data structures with one of:

	use MP3::Info qw(:genres);
	use MP3::Info qw(:DEFAULT :genres);
	use MP3::Info qw(:all);

=cut

sub use_winamp_genres {
	%mp3_genres = %winamp_genres;
	@mp3_genres = @winamp_genres;
	return 1;
}

=pod

=item remove_mp3tag (FILE [, VERSION, BUFFER])

Can remove ID3v1 or ID3v2 tags.  VERSION should be C<1> for ID3v1
(the default), C<2> for ID3v2, and C for both.

For ID3v1, removes last 128 bytes from file if those last 128 bytes begin
with the text 'TAG'.  File will be 128 bytes shorter.

For ID3v2, removes ID3v2 tag.  Because an ID3v2 tag is at the
beginning of the file, we rewrite the file after removing the tag data.
The buffer for rewriting the file is 4MB.  BUFFER (in bytes) ca
change the buffer size.

Returns the number of bytes removed, or -1 if no tag removed,
or undef if there is an error.

=cut

sub remove_mp3tag {
	my($file, $version, $buf) = @_;
	my($fh, $return);

	$buf ||= 4096*1024;  # the bigger the faster
	$version ||= 1;

	if (not (defined $file && $file ne '')) {
		$@ = "No file specified";
		return undef;
	}

	if (not -s $file) {
		$@ = "File is empty";
		return undef;
	}

	if (ref $file) { # filehandle passed
		$fh = $file;
	} else {
		if (not open $fh, '+<', $file) {
			$@ = "Can't open $file: $!";
			return undef;
		}
	}

	binmode $fh;

	if ($version eq 1 || $version eq 'ALL') {
		seek $fh, -128, 2;
		my $tell = tell $fh;
		if (<$fh> =~ /^TAG/) {
			truncate $fh, $tell or carp "Can't truncate '$file': $!";
			$return += 128;
		}
	}

	if ($version eq 2 || $version eq 'ALL') {
		my $v2h = _get_v2head($fh);
		if ($v2h) {
			local $\;
			seek $fh, 0, 2;
			my $eof = tell $fh;
			my $off = $v2h->{tag_size};

			while ($off < $eof) {
				seek $fh, $off, 0;
				read $fh, my($bytes), $buf;
				seek $fh, $off - $v2h->{tag_size}, 0;
				print $fh $bytes;
				$off += $buf;
			}

			truncate $fh, $eof - $v2h->{tag_size}
				or carp "Can't truncate '$file': $!";
			$return += $v2h->{tag_size};
		}
	}

	_close($file, $fh);

	return $return || -1;
}


=pod

=item set_mp3tag (FILE, TITLE, ARTIST, ALBUM, YEAR, COMMENT, GENRE [, TRACKNUM])

=item 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 C<@mp3_genres>.

Will accept either a list of values, or a hashref of the type
returned by C.

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

ID3v2 support may come eventually.  Note that if you set a tag on a file
with ID3v2, the set tag will be for ID3v1[.1] only, and if you call
C on the file, it will show you the (unchanged) ID3v2 tags,
unless you specify ID3v1.

=cut

sub set_mp3tag {
	my($file, $title, $artist, $album, $year, $comment, $genre, $tracknum) = @_;
	my(%info, $oldfh, $ref, $fh);
	local %v1_tag_fields = %v1_tag_fields;

	# set each to '' if undef
	for ($title, $artist, $album, $year, $comment, $tracknum, $genre,
		(@info{@v1_tag_names}))
		{$_ = defined() ? $_ : ''}

	($ref) = (overload::StrVal($title) =~ /^(?:.*\=)?([^=]*)\((?:[^\(]*)\)$/)
		if ref $title;
	# populate data to hashref if hashref is not passed
	if (!$ref) {
		(@info{@v1_tag_names}) =
			($title, $artist, $album, $year, $comment, $tracknum, $genre);

	# put data from hashref into hashref if hashref is passed
	} elsif ($ref eq 'HASH') {
		%info = %$title;

	# return otherwise
	} else {
		carp(<<'EOT');
Usage: set_mp3tag (FILE, TITLE, ARTIST, ALBUM, YEAR, COMMENT, GENRE [, TRACKNUM])
       set_mp3tag (FILE, $HASHREF)
EOT
		return undef;
	}

	if (not (defined $file && $file ne '')) {
		$@ = "No file specified";
		return undef;
	}

	if (not -s $file) {
		$@ = "File is empty";
		return undef;
	}

	# comment field length 28 if ID3v1.1
	$v1_tag_fields{COMMENT} = 28 if $info{TRACKNUM};


	# only if -w is on
	if ($^W) {
		# warn if fields too long
		foreach my $field (keys %v1_tag_fields) {
			$info{$field} = '' unless defined $info{$field};
			if (length($info{$field}) > $v1_tag_fields{$field}) {
				carp "Data too long for field $field: truncated to " .
					 "$v1_tag_fields{$field}";
			}
		}

		if ($info{GENRE}) {
			carp "Genre `$info{GENRE}' does not exist\n"
				unless exists $mp3_genres{$info{GENRE}};
		}
	}

	if ($info{TRACKNUM}) {
		$info{TRACKNUM} =~ s/^(\d+)\/(\d+)$/$1/;
		unless ($info{TRACKNUM} =~ /^\d+$/ &&
			$info{TRACKNUM} > 0 && $info{TRACKNUM} < 256) {
			carp "Tracknum `$info{TRACKNUM}' must be an integer " .
				"from 1 and 255\n" if $^W;
			$info{TRACKNUM} = '';
		}
	}

	if (ref $file) { # filehandle passed
		$fh = $file;
	} else {
		if (not open $fh, '+<', $file) {
			$@ = "Can't open $file: $!";
			return undef;
		}
	}

	binmode $fh;
	$oldfh = select $fh;
	seek $fh, -128, 2;
	# go to end of file if no tag, beginning of file if tag
	seek $fh, (<$fh> =~ /^TAG/ ? -128 : 0), 2;

	# get genre value
	$info{GENRE} = $info{GENRE} && exists $mp3_genres{$info{GENRE}} ?
		$mp3_genres{$info{GENRE}} : 255;  # some default genre

	local $\;
	# print TAG to file
	if ($info{TRACKNUM}) {
		print pack 'a3a30a30a30a4a28xCC', 'TAG', @info{@v1_tag_names};
	} else {
		print pack 'a3a30a30a30a4a30C', 'TAG', @info{@v1_tag_names[0..4, 6]};
	}

	select $oldfh;

	_close($file, $fh);

	return 1;
}

=pod

=item get_mp3tag (FILE [, VERSION, RAW_V2])

Returns hash reference containing tag information in MP3 file.  The keys
returned are the same as those supplied for C, except in the
case of RAW_V2 being set.

If VERSION is C<1>, the information is taken from the ID3v1 tag (if present).
If VERSION is C<2>, the information is taken from the ID3v2 tag (if present).
If VERSION is not supplied, or is false, the ID3v1 tag is read if present, and
then, if present, the ID3v2 tag information will override any existing ID3v1
tag info.

If RAW_V2 is C<1>, the raw ID3v2 tag data is returned, without any manipulation
of text encoding.  The key name is the same as the frame ID (ID to name mappings
are in the global %v2_tag_names).

If RAW_V2 is C<2>, the ID3v2 tag data is returned, manipulating for Unicode if
necessary, etc.  It also takes multiple values for a given key (such as comments)
and puts them in an arrayref.

If the ID3v2 version is older than ID3v2.2.0 or newer than ID3v2.4.0, it will
not be read.

Strings returned will be in Latin-1, unless UTF-8 is specified (L),
(unless RAW_V2 is C<1>).

Also returns a TAGVERSION key, containing the ID3 version used for the returned
data (if TAGVERSION argument is C<0>, may contain two versions).

=cut

sub get_mp3tag {
	my($file, $ver, $raw_v2) = @_;
	my($tag, $v1, $v2, $v2h, %info, @array, $fh);
	$raw_v2 ||= 0;
	$ver = !$ver ? 0 : ($ver == 2 || $ver == 1) ? $ver : 0;

	if (not (defined $file && $file ne '')) {
		$@ = "No file specified";
		return undef;
	}

	if (not -s $file) {
		$@ = "File is empty";
		return undef;
	}

	if (ref $file) { # filehandle passed
		$fh = $file;
	} else {
		if (not open $fh, '<', $file) {
			$@ = "Can't open $file: $!";
			return undef;
		}
	}

	binmode $fh;

	if ($ver < 2) {
		seek $fh, -128, 2;
		while(defined(my $line = <$fh>)) { $tag .= $line }

		if ($tag && $tag =~ /^TAG/) {
			$v1 = 1;
			if (substr($tag, -3, 2) =~ /\000[^\000]/) {
				(undef, @info{@v1_tag_names}) =
					(unpack('a3a30a30a30a4a28', $tag),
					ord(substr($tag, -2, 1)),
					$mp3_genres[ord(substr $tag, -1)]);
				$info{TAGVERSION} = 'ID3v1.1';
			} else {
				(undef, @info{@v1_tag_names[0..4, 6]}) =
					(unpack('a3a30a30a30a4a30', $tag),
					$mp3_genres[ord(substr $tag, -1)]);
				$info{TAGVERSION} = 'ID3v1';
			}
			if ($UNICODE) {
				for my $key (keys %info) {
					next unless $info{$key};
					$info{$key} = Encode::encode_utf8($info{$key});
				}
			}
		} elsif ($ver == 1) {
			_close($file, $fh);
			$@ = "No ID3v1 tag found";
			return undef;
		}
	}

	($v2, $v2h) = _get_v2tag($fh);

	unless ($v1 || $v2) {
		_close($file, $fh);
		$@ = "No ID3 tag found";
		return undef;
	}

	if (($ver == 0 || $ver == 2) && $v2) {
		if ($raw_v2 == 1 && $ver == 2) {
			%info = %$v2;
			$info{TAGVERSION} = $v2h->{version};
		} else {
			my $hash = $raw_v2 == 2 ? { map { ($_, $_) } keys %v2_tag_names } : \%v2_to_v1_names;
			for my $id (keys %$hash) {
				if (exists $v2->{$id}) {
					my $data1 = $v2->{$id};

					# this is tricky ... if this is an arrayref,
					# we want to only return one, so we pick the
					# first one.  but if it is a comment, we pick
					# the first one where the first charcter after
					# the language is NULL and not an additional
					# sub-comment, because that is most likely to be
					# the user-supplied comment
					if (ref $data1 && !$raw_v2) {
						if ($id =~ /^COMM?$/) {
							my($newdata) = grep /^(....\000)/, @{$data1};
							$data1 = $newdata || $data1->[0];
						} else {
							$data1 = $data1->[0];
						}
					}

					$data1 = [ $data1 ] if ! ref $data1;

					for my $data (@$data1) {
						# TODO : this should only be done for certain frames;
						# using RAW still gives you access, but we should be smarter
						# about how individual frame types are handled.  it's not
						# like the list is infinitely long.
						$data =~ s/^(.)//; # strip first char (text encoding)
						my $encoding = $1;
						my $desc;
						if ($id =~ /^COM[M ]?$/) { # space for iTunes brokenness
							$data =~ s/^(?:...)//;		# strip language
						}

						if ($UNICODE) {
							if ($encoding eq "\001" || $encoding eq "\002") {  # UTF-16, UTF-16BE
								# text fields can be null-separated lists;
								# UTF-16 therefore needs special care
								#
								# foobar2000 encodes tags in UTF-16LE
								# (which is apparently illegal)
								# Encode dies on a bad BOM, so it is
								# probably wise to wrap it in an eval
								# anyway
								$data = eval { Encode::decode('utf16', $data) } || Encode::decode('utf16le', $data);
								# this split we do doesn't work, because obviously
								# two NULLs can appear where we don't want ...
								#$data = join "\000", map {
								#	eval { Encode::decode('utf16', $_) } || Encode::decode('utf16le', $_)
								#} split /\000\000/, $data;

							} elsif ($encoding eq "\003") { # UTF-8
								# make sure string is UTF8, and set flag appropriately
								$data = Encode::decode('utf8', $data);
							} elsif ($encoding eq "\000") {
								# Try and guess the encoding, otherwise just use latin1
								my $dec = Encode::Guess->guess($data);
								if (ref $dec) {
									$data = $dec->decode($data);
								} else {
									# Best try
									$data = Encode::decode('iso-8859-1', $data);
								}
							}

							# do we care about trailing NULL?
							# $data =~ s/\000$//;

						} else {
							# If the string starts with an
							# UTF-16 little endian BOM, use a hack to
							# convert to ASCII per best-effort
							my $pat;
							if ($data =~ s/^\xFF\xFE//) {
								$pat = 'v';
							} elsif ($data =~ s/^\xFE\xFF//) {
								$pat = 'n';
							}
							if ($pat) {
								$data = pack 'C*', map {
									(chr =~ /[[:ascii:]]/ && chr =~ /[[:print:]]/)
										? $_
										: ord('?')
								} unpack "$pat*", $data;
							}
						}

						# We do this after decoding so we could be certain we're dealing
						# with 8-bit text.
						if ($id =~ /^COM[M ]?$/) { # space for iTunes brokenness
							$data =~ s/^(.*?)\000//;	# strip up to first NULL(s),
											# for sub-comments (TODO:
											# handle all comment data)
							$desc = $1;
						} elsif ($id =~ /^TCON?$/) {
							if ($data =~ /^ \(? (\d+) (?:\)|\000)? (.+)?/sx) {
								my($index, $name) = ($1, $2);
								if ($name && $name ne "\000") {
									$data = $name;
								} else {
									$data = $mp3_genres[$index];
								}
							}
						}

						if ($raw_v2 == 2 && $desc) {
							$data = { $desc => $data };
						}

						if ($raw_v2 == 2 && exists $info{$hash->{$id}}) {
							if (ref $info{$hash->{$id}} eq 'ARRAY') {
								push @{$info{$hash->{$id}}}, $data;
							} else {
								$info{$hash->{$id}} = [ $info{$hash->{$id}}, $data ];
							}
						} else {
							$info{$hash->{$id}} = $data;
						}
					}
				}
			}
			if ($ver == 0 && $info{TAGVERSION}) {
				$info{TAGVERSION} .= ' / ' . $v2h->{version};
			} else {
				$info{TAGVERSION} = $v2h->{version};
			}
		}
	}

	unless ($raw_v2 && $ver == 2) {
		foreach my $key (keys %info) {
			if (defined $info{$key}) {
				$info{$key} =~ s/\000+.*//g;
				$info{$key} =~ s/\s+$//;
			}
		}

		for (@v1_tag_names) {
			$info{$_} = '' unless defined $info{$_};
		}
	}

	if (keys %info && exists $info{GENRE} && ! defined $info{GENRE}) {
		$info{GENRE} = '';
	}

	_close($file, $fh);

	return keys %info ? {%info} : undef;
}

sub _get_v2tag {
	my($fh) = @_;
	my($off, $end, $myseek, $v2, $v2h, $hlen, $num, $wholetag);

	$v2 = {};
	$v2h = _get_v2head($fh) or return;

	if ($v2h->{major_version} < 2) {
		carp "This is $v2h->{version}; " .
		     "ID3v2 versions older than ID3v2.2.0 not supported\n"
		     if $^W;
		return;
	}

	# use syncsafe bytes if using version 2.4
	my $bytesize = ($v2h->{major_version} > 3) ? 128 : 256;

	if ($v2h->{major_version} == 2) {
		$hlen = 6;
		$num = 3;
	} else {
		$hlen = 10;
		$num = 4;
	}

	$off = $v2h->{ext_header_size} + 10;
	$end = $v2h->{tag_size} + 10; # should we read in the footer too?

	seek $fh, $v2h->{offset}, 0;
	read $fh, $wholetag, $end;

	$wholetag =~ s/\xFF\x00/\xFF/gs if $v2h->{unsync};

	$myseek = sub {
		my $bytes = substr($wholetag, $off, $hlen);
		return unless $bytes =~ /^([A-Z0-9]{$num})/
			|| ($num == 4 && $bytes =~ /^(COM )/);  # stupid iTunes
		my($id, $size) = ($1, $hlen);
		my @bytes = reverse unpack "C$num", substr($bytes, $num, $num);

		for my $i (0 .. ($num - 1)) {
			$size += $bytes[$i] * $bytesize ** $i;
		}

		my $flags = {};
		if ($v2h->{major_version} > 3) {
			my @bits = split //, unpack 'B16', substr($bytes, 8, 2);
			$flags->{frame_unsync}       = $bits[14];
			$flags->{data_len_indicator} = $bits[15];
		}

		return($id, $size, $flags);
	};

	while ($off < $end) {
		my($id, $size, $flags) = &$myseek or last;

		my $bytes = substr($wholetag, $off+$hlen, $size-$hlen);

		my $data_len;
		if ($flags->{data_len_indicator}) {
			$data_len = 0;
			my @data_len_bytes = reverse unpack 'C4', substr($bytes, 0, 4);
			$bytes = substr($bytes, 4);
		        for my $i (0..3) {
				$data_len += $data_len_bytes[$i] * 128 ** $i;
		        }
		}

		# perform frame-level unsync if needed (skip if already done for whole tag)
		$bytes =~ s/\xFF\x00/\xFF/gs if $flags->{frame_unsync} && !$v2h->{unsync};

		# if we know the data length, sanity check it now.
		if ($flags->{data_len_indicator} && defined $data_len) {
		        carp "Size mismatch on $id\n" unless $data_len == length($bytes);
		}

		if (exists $v2->{$id}) {
			if (ref $v2->{$id} eq 'ARRAY') {
				push @{$v2->{$id}}, $bytes;
			} else {
				$v2->{$id} = [$v2->{$id}, $bytes];
			}
		} else {
			$v2->{$id} = $bytes;
		}
		$off += $size;
	}

	return($v2, $v2h);
}


=pod

=item get_mp3info (FILE)

Returns hash reference containing file information for MP3 file.
This data cannot be changed.  Returned data:

	VERSION		MPEG audio version (1, 2, 2.5)
	LAYER		MPEG layer description (1, 2, 3)
	STEREO		boolean for audio is in stereo

	VBR		boolean for variable bitrate
	BITRATE		bitrate in kbps (average for VBR files)
	FREQUENCY	frequency in kHz
	SIZE		bytes in audio stream
	OFFSET		bytes offset that stream begins

	SECS		total seconds
	MM		minutes
	SS		leftover seconds
	MS		leftover milliseconds
	TIME		time in MM:SS

	COPYRIGHT	boolean for audio is copyrighted
	PADDING		boolean for MP3 frames are padded
	MODE		channel mode (0 = stereo, 1 = joint stereo,
			2 = dual channel, 3 = single channel)
	FRAMES		approximate number of frames
	FRAME_LENGTH	approximate length of a frame
	VBR_SCALE	VBR scale from VBR header

On error, returns nothing and sets C<$@>.

=cut

sub get_mp3info {
	my($file) = @_;
	my($off, $byte, $eof, $h, $tot, $fh);

	if (not (defined $file && $file ne '')) {
		$@ = "No file specified";
		return undef;
	}

	if (not -s $file) {
		$@ = "File is empty";
		return undef;
	}

	if (ref $file) { # filehandle passed
		$fh = $file;
	} else {
		if (not open $fh, '<', $file) {
			$@ = "Can't open $file: $!";
			return undef;
		}
	}

	$off = 0;
	$tot = 8192;

	binmode $fh;
	seek $fh, $off, 0;
	read $fh, $byte, 4;

	if ($off == 0) {
		if (my $v2h = _get_v2head($fh)) {
			$tot += $off += $v2h->{tag_size};
			seek $fh, $off, 0;
			read $fh, $byte, 4;
		}
	}

	$h = _get_head($byte);
	my $is_mp3 = _is_mp3($h);
	until ($is_mp3) {
		$off++;
		seek $fh, $off, 0;
		read $fh, $byte, 4;
		if ($off > $tot && !$try_harder) {
			_close($file, $fh);
			$@ = "Couldn't find MP3 header (perhaps set " .
			     '$MP3::Info::try_harder and retry)';
			return undef;
		}
		next if ord($byte) != 0xFF;
		$h = _get_head($byte);
		$is_mp3 = _is_mp3($h);
	}

	my $vbr = _get_vbr($fh, $h, \$off);

	seek $fh, 0, 2;
	$eof = tell $fh;
	seek $fh, -128, 2;
	$eof -= 128 if <$fh> =~ /^TAG/ ? 1 : 0;

	_close($file, $fh);

	$h->{size} = $eof - $off;
	$h->{offset} = $off;

	return _get_info($h, $vbr);
}

sub _get_info {
	my($h, $vbr) = @_;
	my $i;

	$i->{VERSION}	= $h->{IDR} == 2 ? 2 : $h->{IDR} == 3 ? 1 :
				$h->{IDR} == 0 ? 2.5 : 0;
	$i->{LAYER}	= 4 - $h->{layer};
	$i->{VBR}	= defined $vbr ? 1 : 0;

	$i->{COPYRIGHT}	= $h->{copyright} ? 1 : 0;
	$i->{PADDING}	= $h->{padding_bit} ? 1 : 0;
	$i->{STEREO}	= $h->{mode} == 3 ? 0 : 1;
	$i->{MODE}	= $h->{mode};

	$i->{SIZE}	= $vbr && $vbr->{bytes} ? $vbr->{bytes} : $h->{size};
	$i->{OFFSET}	= $h->{offset};

	my $mfs		= $h->{fs} / ($h->{ID} ? 144000 : 72000);
	$i->{FRAMES}	= int($vbr && $vbr->{frames}
				? $vbr->{frames}
				: $i->{SIZE} / ($h->{bitrate} / $mfs)
			  );

	if ($vbr) {
		$i->{VBR_SCALE}	= $vbr->{scale} if $vbr->{scale};
		$h->{bitrate}	= $i->{SIZE} / $i->{FRAMES} * $mfs;
		if (not $h->{bitrate}) {
			$@ = "Couldn't determine VBR bitrate";
			return undef;
		}
	}

	$h->{'length'}	= ($i->{SIZE} * 8) / $h->{bitrate} / 10;
	$i->{SECS}	= $h->{'length'} / 100;
	$i->{MM}	= int $i->{SECS} / 60;
	$i->{SS}	= int $i->{SECS} % 60;
	$i->{MS}	= (($i->{SECS} - ($i->{MM} * 60) - $i->{SS}) * 1000);
#	$i->{LF}	= ($i->{MS} / 1000) * ($i->{FRAMES} / $i->{SECS});
#	int($i->{MS} / 100 * 75);  # is this right?
	$i->{TIME}	= sprintf "%.2d:%.2d", @{$i}{'MM', 'SS'};

	$i->{BITRATE}		= int $h->{bitrate};
	# should we just return if ! FRAMES?
	$i->{FRAME_LENGTH}	= int($h->{size} / $i->{FRAMES}) if $i->{FRAMES};
	$i->{FREQUENCY}		= $frequency_tbl[3 * $h->{IDR} + $h->{sampling_freq}];

	return $i;
}

sub _get_head {
	my($byte) = @_;
	my($bytes, $h);

	$bytes = _unpack_head($byte);
	@$h{qw(IDR ID layer protection_bit
		bitrate_index sampling_freq padding_bit private_bit
		mode mode_extension copyright original
		emphasis version_index bytes)} = (
		($bytes>>19)&3, ($bytes>>19)&1, ($bytes>>17)&3, ($bytes>>16)&1,
		($bytes>>12)&15, ($bytes>>10)&3, ($bytes>>9)&1, ($bytes>>8)&1,
		($bytes>>6)&3, ($bytes>>4)&3, ($bytes>>3)&1, ($bytes>>2)&1,
		$bytes&3, ($bytes>>19)&3, $bytes
	);

	$h->{bitrate} = $t_bitrate[$h->{ID}][3 - $h->{layer}][$h->{bitrate_index}];
	$h->{fs} = $t_sampling_freq[$h->{IDR}][$h->{sampling_freq}];

	return $h;
}

sub _is_mp3 {
	my $h = $_[0] or return undef;
	return ! (	# all below must be false
		 $h->{bitrate_index} == 0
			||
		 $h->{version_index} == 1
			||
		($h->{bytes} & 0xFFE00000) != 0xFFE00000
			||
		!$h->{fs}
			||
		!$h->{bitrate}
			||
		 $h->{bitrate_index} == 15
			||
		!$h->{layer}
			||
		 $h->{sampling_freq} == 3
			||
		 $h->{emphasis} == 2
			||
		!$h->{bitrate_index}
			||
		($h->{bytes} & 0xFFFF0000) == 0xFFFE0000
			||
		($h->{ID} == 1 && $h->{layer} == 3 && $h->{protection_bit} == 1)
			||
		($h->{mode_extension} != 0 && $h->{mode} != 1)
	);
}

sub _get_vbr {
	my($fh, $h, $roff) = @_;
	my($off, $bytes, @bytes, $myseek, %vbr);

	$off = $$roff;
	@_ = ();	# closure confused if we don't do this

	$myseek = sub {
		my $n = $_[0] || 4;
		seek $fh, $off, 0;
		read $fh, $bytes, $n;
		$off += $n;
	};

	$off += 4;

	if ($h->{ID}) {	# MPEG1
		$off += $h->{mode} == 3 ? 17 : 32;
	} else {	# MPEG2
		$off += $h->{mode} == 3 ? 9 : 17;
	}

	&$myseek;
	return unless $bytes eq 'Xing';

	&$myseek;
	$vbr{flags} = _unpack_head($bytes);

	if ($vbr{flags} & 1) {
		&$myseek;
		$vbr{frames} = _unpack_head($bytes);
	}

	if ($vbr{flags} & 2) {
		&$myseek;
		$vbr{bytes} = _unpack_head($bytes);
	}

	if ($vbr{flags} & 4) {
		$myseek->(100);
# Not used right now ...
#		$vbr{toc} = _unpack_head($bytes);
	}

	if ($vbr{flags} & 8) { # (quality ind., 0=best 100=worst)
		&$myseek;
		$vbr{scale} = _unpack_head($bytes);
	} else {
		$vbr{scale} = -1;
	}

	$$roff = $off;
	return \%vbr;
}

sub _get_v2head {
	my $fh = $_[0] or return;
	my($v2h, $bytes, @bytes);
	$v2h->{offset} = 0;

	# check first three bytes for 'ID3'
	seek $fh, 0, 0;
	read $fh, $bytes, 3;

	# TODO: add support for tags at the end of the file
	if ($bytes eq 'RIF' || $bytes eq 'FOR') {
		_find_id3_chunk($fh, $bytes) or return;
		$v2h->{offset} = tell $fh;
		read $fh, $bytes, 3;
	}

	return unless $bytes eq 'ID3';

	# get version
	read $fh, $bytes, 2;
	$v2h->{version} = sprintf "ID3v2.%d.%d",
		@$v2h{qw[major_version minor_version]} =
			unpack 'c2', $bytes;

	# get flags
	read $fh, $bytes, 1;
	my @bits = split //, unpack 'b8', $bytes;
	if ($v2h->{major_version} == 2) {
		$v2h->{unsync}       = $bits[7];
		$v2h->{compression}  = $bits[8];
		$v2h->{ext_header}   = 0;
		$v2h->{experimental} = 0;
	} else {
		$v2h->{unsync}       = $bits[7];
		$v2h->{ext_header}   = $bits[6];
		$v2h->{experimental} = $bits[5];
		$v2h->{footer}       = $bits[4] if $v2h->{major_version} == 4;
	}

	# get ID3v2 tag length from bytes 7-10
	$v2h->{tag_size} = 10;	# include ID3v2 header size
	$v2h->{tag_size} += 10 if $v2h->{footer};
	read $fh, $bytes, 4;
	@bytes = reverse unpack 'C4', $bytes;
	foreach my $i (0 .. 3) {
		# whoaaaaaa nellllllyyyyyy!
		$v2h->{tag_size} += $bytes[$i] * 128 ** $i;
	}

	# get extended header size
	$v2h->{ext_header_size} = 0;
	if ($v2h->{ext_header}) {
		read $fh, $bytes, 4;
		@bytes = reverse unpack 'C4', $bytes;

		# use syncsafe bytes if using version 2.4
		my $bytesize = ($v2h->{major_version} > 3) ? 128 : 256;
		for my $i (0..3) {
			$v2h->{ext_header_size} += $bytes[$i] * $bytesize ** $i;
		}
	}

	return $v2h;
}

sub _find_id3_chunk {
	my($fh, $filetype) = @_;
	my($bytes, $size, $tag, $pat, $mat);

	read $fh, $bytes, 1;
	if ($filetype eq 'RIF') {  # WAV
		return 0 if $bytes ne 'F';
		$pat = 'a4V';
		$mat = 'id3 ';
	} elsif ($filetype eq 'FOR') { # AIFF
		return 0 if $bytes ne 'M';
		$pat = 'a4N';
		$mat = 'ID3 ';
	}
	seek $fh, 12, 0;  # skip to the first chunk

	while ((read $fh, $bytes, 8) == 8) {
		($tag, $size)  = unpack $pat, $bytes;
		return 1 if $tag eq $mat;
		seek $fh, $size, 1;
	}

	return 0;
}

sub _unpack_head {
	unpack('l', pack('L', unpack('N', $_[0])));
}

sub _close {
	my($file, $fh) = @_;
	unless (ref $file) { # filehandle not passed
		close $fh or carp "Problem closing '$file': $!";
	}
}

BEGIN {
	@mp3_genres = (
		'Blues',
		'Classic Rock',
		'Country',
		'Dance',
		'Disco',
		'Funk',
		'Grunge',
		'Hip-Hop',
		'Jazz',
		'Metal',
		'New Age',
		'Oldies',
		'Other',
		'Pop',
		'R&B',
		'Rap',
		'Reggae',
		'Rock',
		'Techno',
		'Industrial',
		'Alternative',
		'Ska',
		'Death Metal',
		'Pranks',
		'Soundtrack',
		'Euro-Techno',
		'Ambient',
		'Trip-Hop',
		'Vocal',
		'Jazz+Funk',
		'Fusion',
		'Trance',
		'Classical',
		'Instrumental',
		'Acid',
		'House',
		'Game',
		'Sound Clip',
		'Gospel',
		'Noise',
		'AlternRock',
		'Bass',
		'Soul',
		'Punk',
		'Space',
		'Meditative',
		'Instrumental Pop',
		'Instrumental Rock',
		'Ethnic',
		'Gothic',
		'Darkwave',
		'Techno-Industrial',
		'Electronic',
		'Pop-Folk',
		'Eurodance',
		'Dream',
		'Southern Rock',
		'Comedy',
		'Cult',
		'Gangsta',
		'Top 40',
		'Christian Rap',
		'Pop/Funk',
		'Jungle',
		'Native American',
		'Cabaret',
		'New Wave',
		'Psychadelic',
		'Rave',
		'Showtunes',
		'Trailer',
		'Lo-Fi',
		'Tribal',
		'Acid Punk',
		'Acid Jazz',
		'Polka',
		'Retro',
		'Musical',
		'Rock & Roll',
		'Hard Rock',
	);

	@winamp_genres = (
		@mp3_genres,
		'Folk',
		'Folk-Rock',
		'National Folk',
		'Swing',
		'Fast Fusion',
		'Bebop',
		'Latin',
		'Revival',
		'Celtic',
		'Bluegrass',
		'Avantgarde',
		'Gothic Rock',
		'Progressive Rock',
		'Psychedelic Rock',
		'Symphonic Rock',
		'Slow Rock',
		'Big Band',
		'Chorus',
		'Easy Listening',
		'Acoustic',
		'Humour',
		'Speech',
		'Chanson',
		'Opera',
		'Chamber Music',
		'Sonata',
		'Symphony',
		'Booty Bass',
		'Primus',
		'Porn Groove',
		'Satire',
		'Slow Jam',
		'Club',
		'Tango',
		'Samba',
		'Folklore',
		'Ballad',
		'Power Ballad',
		'Rhythmic Soul',
		'Freestyle',
		'Duet',
		'Punk Rock',
		'Drum Solo',
		'Acapella',
		'Euro-House',
		'Dance Hall',
		'Goa',
		'Drum & Bass',
		'Club-House',
		'Hardcore',
		'Terror',
		'Indie',
		'BritPop',
		'Negerpunk',
		'Polsk Punk',
		'Beat',
		'Christian Gangsta Rap',
		'Heavy Metal',
		'Black Metal',
		'Crossover',
		'Contemporary Christian',
		'Christian Rock',
		'Merengue',
		'Salsa',
		'Thrash Metal',
		'Anime',
		'JPop',
		'Synthpop',
	);

	@t_bitrate = ([
		[0, 32, 48, 56,  64,  80,  96, 112, 128, 144, 160, 176, 192, 224, 256],
		[0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128, 144, 160],
		[0,  8, 16, 24,  32,  40,  48,  56,  64,  80,  96, 112, 128, 144, 160]
	],[
		[0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448],
		[0, 32, 48, 56,  64,  80,  96, 112, 128, 160, 192, 224, 256, 320, 384],
		[0, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 224, 256, 320]
	]);

	@t_sampling_freq = (
		[11025, 12000,  8000],
		[undef, undef, undef],	# reserved
		[22050, 24000, 16000],
		[44100, 48000, 32000]
	);

	@frequency_tbl = map { $_ ? eval "${_}e-3" : 0 }
		map { @$_ } @t_sampling_freq;

	@mp3_info_fields = qw(
		VERSION
		LAYER
		STEREO
		VBR
		BITRATE
		FREQUENCY
		SIZE
		OFFSET
		SECS
		MM
		SS
		MS
		TIME
		COPYRIGHT
		PADDING
		MODE
		FRAMES
		FRAME_LENGTH
		VBR_SCALE
	);

	%v1_tag_fields =
		(TITLE => 30, ARTIST => 30, ALBUM => 30, COMMENT => 30, YEAR => 4);

	@v1_tag_names = qw(TITLE ARTIST ALBUM YEAR COMMENT TRACKNUM GENRE);

	%v2_to_v1_names = (
		# v2.2 tags
		'TT2' => 'TITLE',
		'TP1' => 'ARTIST',
		'TAL' => 'ALBUM',
		'TYE' => 'YEAR',
		'COM' => 'COMMENT',
		'TRK' => 'TRACKNUM',
		'TCO' => 'GENRE', # not clean mapping, but ...
		# v2.3 tags
		'TIT2' => 'TITLE',
		'TPE1' => 'ARTIST',
		'TALB' => 'ALBUM',
		'TYER' => 'YEAR',
		'COMM' => 'COMMENT',
		'TRCK' => 'TRACKNUM',
		'TCON' => 'GENRE',
	);

	%v2_tag_names = (
		# v2.2 tags
		'BUF' => 'Recommended buffer size',
		'CNT' => 'Play counter',
		'COM' => 'Comments',
		'CRA' => 'Audio encryption',
		'CRM' => 'Encrypted meta frame',
		'ETC' => 'Event timing codes',
		'EQU' => 'Equalization',
		'GEO' => 'General encapsulated object',
		'IPL' => 'Involved people list',
		'LNK' => 'Linked information',
		'MCI' => 'Music CD Identifier',
		'MLL' => 'MPEG location lookup table',
		'PIC' => 'Attached picture',
		'POP' => 'Popularimeter',
		'REV' => 'Reverb',
		'RVA' => 'Relative volume adjustment',
		'SLT' => 'Synchronized lyric/text',
		'STC' => 'Synced tempo codes',
		'TAL' => 'Album/Movie/Show title',
		'TBP' => 'BPM (Beats Per Minute)',
		'TCM' => 'Composer',
		'TCO' => 'Content type',
		'TCR' => 'Copyright message',
		'TDA' => 'Date',
		'TDY' => 'Playlist delay',
		'TEN' => 'Encoded by',
		'TFT' => 'File type',
		'TIM' => 'Time',
		'TKE' => 'Initial key',
		'TLA' => 'Language(s)',
		'TLE' => 'Length',
		'TMT' => 'Media type',
		'TOA' => 'Original artist(s)/performer(s)',
		'TOF' => 'Original filename',
		'TOL' => 'Original Lyricist(s)/text writer(s)',
		'TOR' => 'Original release year',
		'TOT' => 'Original album/Movie/Show title',
		'TP1' => 'Lead artist(s)/Lead performer(s)/Soloist(s)/Performing group',
		'TP2' => 'Band/Orchestra/Accompaniment',
		'TP3' => 'Conductor/Performer refinement',
		'TP4' => 'Interpreted, remixed, or otherwise modified by',
		'TPA' => 'Part of a set',
		'TPB' => 'Publisher',
		'TRC' => 'ISRC (International Standard Recording Code)',
		'TRD' => 'Recording dates',
		'TRK' => 'Track number/Position in set',
		'TSI' => 'Size',
		'TSS' => 'Software/hardware and settings used for encoding',
		'TT1' => 'Content group description',
		'TT2' => 'Title/Songname/Content description',
		'TT3' => 'Subtitle/Description refinement',
		'TXT' => 'Lyricist/text writer',
		'TXX' => 'User defined text information frame',
		'TYE' => 'Year',
		'UFI' => 'Unique file identifier',
		'ULT' => 'Unsychronized lyric/text transcription',
		'WAF' => 'Official audio file webpage',
		'WAR' => 'Official artist/performer webpage',
		'WAS' => 'Official audio source webpage',
		'WCM' => 'Commercial information',
		'WCP' => 'Copyright/Legal information',
		'WPB' => 'Publishers official webpage',
		'WXX' => 'User defined URL link frame',

		# v2.3 tags
		'AENC' => 'Audio encryption',
		'APIC' => 'Attached picture',
		'COMM' => 'Comments',
		'COMR' => 'Commercial frame',
		'ENCR' => 'Encryption method registration',
		'EQUA' => 'Equalization',
		'ETCO' => 'Event timing codes',
		'GEOB' => 'General encapsulated object',
		'GRID' => 'Group identification registration',
		'IPLS' => 'Involved people list',
		'LINK' => 'Linked information',
		'MCDI' => 'Music CD identifier',
		'MLLT' => 'MPEG location lookup table',
		'OWNE' => 'Ownership frame',
		'PCNT' => 'Play counter',
		'POPM' => 'Popularimeter',
		'POSS' => 'Position synchronisation frame',
		'PRIV' => 'Private frame',
		'RBUF' => 'Recommended buffer size',
		'RVAD' => 'Relative volume adjustment',
		'RVRB' => 'Reverb',
		'SYLT' => 'Synchronized lyric/text',
		'SYTC' => 'Synchronized tempo codes',
		'TALB' => 'Album/Movie/Show title',
		'TBPM' => 'BPM (beats per minute)',
		'TCOM' => 'Composer',
		'TCON' => 'Content type',
		'TCOP' => 'Copyright message',
		'TDAT' => 'Date',
		'TDLY' => 'Playlist delay',
		'TENC' => 'Encoded by',
		'TEXT' => 'Lyricist/Text writer',
		'TFLT' => 'File type',
		'TIME' => 'Time',
		'TIT1' => 'Content group description',
		'TIT2' => 'Title/songname/content description',
		'TIT3' => 'Subtitle/Description refinement',
		'TKEY' => 'Initial key',
		'TLAN' => 'Language(s)',
		'TLEN' => 'Length',
		'TMED' => 'Media type',
		'TOAL' => 'Original album/movie/show title',
		'TOFN' => 'Original filename',
		'TOLY' => 'Original lyricist(s)/text writer(s)',
		'TOPE' => 'Original artist(s)/performer(s)',
		'TORY' => 'Original release year',
		'TOWN' => 'File owner/licensee',
		'TPE1' => 'Lead performer(s)/Soloist(s)',
		'TPE2' => 'Band/orchestra/accompaniment',
		'TPE3' => 'Conductor/performer refinement',
		'TPE4' => 'Interpreted, remixed, or otherwise modified by',
		'TPOS' => 'Part of a set',
		'TPUB' => 'Publisher',
		'TRCK' => 'Track number/Position in set',
		'TRDA' => 'Recording dates',
		'TRSN' => 'Internet radio station name',
		'TRSO' => 'Internet radio station owner',
		'TSIZ' => 'Size',
		'TSRC' => 'ISRC (international standard recording code)',
		'TSSE' => 'Software/Hardware and settings used for encoding',
		'TXXX' => 'User defined text information frame',
		'TYER' => 'Year',
		'UFID' => 'Unique file identifier',
		'USER' => 'Terms of use',
		'USLT' => 'Unsychronized lyric/text transcription',
		'WCOM' => 'Commercial information',
		'WCOP' => 'Copyright/Legal information',
		'WOAF' => 'Official audio file webpage',
		'WOAR' => 'Official artist/performer webpage',
		'WOAS' => 'Official audio source webpage',
		'WORS' => 'Official internet radio station homepage',
		'WPAY' => 'Payment',
		'WPUB' => 'Publishers official webpage',
		'WXXX' => 'User defined URL link frame',

		# v2.4 additional tags
		# note that we don't restrict tags from 2.3 or 2.4,
		'ASPI' => 'Audio seek point index',
		'EQU2' => 'Equalisation (2)',
		'RVA2' => 'Relative volume adjustment (2)',
		'SEEK' => 'Seek frame',
		'SIGN' => 'Signature frame',
		'TDEN' => 'Encoding time',
		'TDOR' => 'Original release time',
		'TDRC' => 'Recording time',
		'TDRL' => 'Release time',
		'TDTG' => 'Tagging time',
		'TIPL' => 'Involved people list',
		'TMCL' => 'Musician credits list',
		'TMOO' => 'Mood',
		'TPRO' => 'Produced notice',
		'TSOA' => 'Album sort order',
		'TSOP' => 'Performer sort order',
		'TSOT' => 'Title sort order',
		'TSST' => 'Set subtitle',

		# grrrrrrr
		'COM ' => 'Broken iTunes comments',
	);
}

1;

__END__