#------------------------------------------------------------------------------
# File: FLAC.pm
#
# Description: Read Free Lossless Audio Codec information
#
# Revisions: 11/13/2006 - P. Harvey Created
#
# References: 1) http://flac.sourceforge.net/
#------------------------------------------------------------------------------
package Image::ExifTool::FLAC;
use strict;
use vars qw($VERSION);
use Image::ExifTool qw(:DataAccess :Utils);
$VERSION = '1.01';
sub ProcessBitStream($$$);
# FLAC metadata blocks
%Image::ExifTool::FLAC::Main = (
NOTES => q{
Free Lossless Audio Codec (FLAC) meta information. ExifTool also extracts
ID3 information from these files.
},
0 => {
Name => 'StreamInfo',
SubDirectory => { TagTable => 'Image::ExifTool::FLAC::StreamInfo' },
},
4 => {
Name => 'VorbisComment',
SubDirectory => { TagTable => 'Image::ExifTool::Vorbis::Comments' },
},
);
%Image::ExifTool::FLAC::StreamInfo = (
PROCESS_PROC => \&ProcessBitStream,
NOTES => 'FLAC is big-endian, so bit 0 is the high-order bit in this table.',
GROUPS => { 2 => 'Audio' },
'Bit000-015' => 'BlockSizeMin',
'Bit016-031' => 'BlockSizeMax',
'Bit032-055' => 'FrameSizeMin',
'Bit056-079' => 'FrameSizeMax',
'Bit080-099' => 'SampleRate',
'Bit100-102' => {
Name => 'Channels',
ValueConv => '$val + 1',
},
'Bit103-107' => {
Name => 'BitsPerSample',
ValueConv => '$val + 1',
},
'Bit108-143' => 'TotalSamples',
);
# FLAC composite tags
%Image::ExifTool::FLAC::Composite = (
Duration => {
Require => {
0 => 'FLAC:SampleRate',
1 => 'FLAC:Channels',
2 => 'FLAC:TotalSamples',
},
ValueConv => '$val[0] and $val[1] and $val[2] ? $val[2] / ($val[0] * $val[1]) : undef',
PrintConv => 'ConvertDuration($val)',
},
);
# add our composite tags
Image::ExifTool::AddCompositeTags('Image::ExifTool::FLAC');
#------------------------------------------------------------------------------
# Process information in a bit stream
# Inputs: 0) ExifTool object ref, 1) dirInfo ref, 2) tag table ref
# Notes: Byte order is used to determine the ordering of bits in the stream:
# 'MM' = bit 0 is most significant, 'II' = bit 0 is least significant
# - can handle arbitrarily wide values (ie. 8-byte or larger integers)
sub ProcessBitStream($$$)
{
my ($exifTool, $dirInfo, $tagTablePtr) = @_;
my $dataPt = $$dirInfo{DataPt};
my $dataPos = $$dirInfo{DataPos};
my $dirStart = $$dirInfo{DirStart} || 0;
my $dirLen = $$dirInfo{DirLen} || (length($$dataPt) - $dirStart);
my $verbose = $exifTool->Options('Verbose');
my $byteOrder = GetByteOrder();
my $tag;
if ($verbose) {
$exifTool->VPrint(0, " + [BitStream directory, $dirLen bytes, '$byteOrder' order]\n");
}
foreach $tag (sort keys %$tagTablePtr) {
next unless $tag =~ /^Bit(\d+)-?(\d+)?/;
my ($b1, $b2) = ($1, $2 || $1); # start/end bit numbers in stream
my ($i1, $i2) = (int($b1 / 8), int($b2 / 8)); # start/end byte numbers
my ($f1, $f2) = ($b1 % 8, $b2 % 8); # start/end bit numbers within each byte
last if $i2 >= $dirLen;
my $val = 0;
my ($i, $mask, $extra);
$extra = ', Mask=0x' if $verbose and ($f1 != 0 or $f2 != 7);
if ($byteOrder eq 'MM') {
# loop from high byte to low byte
for ($i=$i1; $i<=$i2; ++$i) {
$mask = 0xff;
if ($i == $i1 and $f1) {
# mask off high bits in first word (0 is high bit)
foreach ((8-$f1) .. 7) { $mask ^= (1 << $_) }
}
if ($i == $i2 and $f2 < 7) {
# mask off low bits in last word (7 is low bit)
foreach (0 .. (6-$f2)) { $mask ^= (1 << $_) }
}
$val = $val * 256 + ($mask & Get8u($dataPt, $i + $dirStart));
$extra .= sprintf('%.2x', $mask) if $extra;
}
} else {
# (FLAC is big-endian, but support little-endian bit streams
# so this routine can be used by other modules)
# loop from high byte to low byte
for ($i=$i2; $i>=$i1; --$i) {
$mask = 0xff;
if ($i == $i1 and $f1) {
# mask off low bits in first word (0 is low bit)
foreach (0 .. ($f1-1)) { $mask ^= (1 << $_) }
}
if ($i == $i2 and $f2 < 7) {
# mask off high bits in last word (7 is high bit)
foreach (($f2+1) .. 7) { $mask ^= (1 << $_) }
}
$val = $val * 256 + ($mask & Get8u($dataPt, $i + $dirStart));
$extra .= sprintf('%.2x', $mask) if $extra;
}
}
# shift word down until low bit is in position 0
until ($mask & 0x01) {
$val /= 2;
$mask >>= 1;
}
$exifTool->HandleTag($tagTablePtr, $tag, $val,
DataPt => $dataPt,
DataPos => $dataPos,
Start => $dirStart + $i1,
Size => $i2 - $i1 + 1,
Extra => $extra,
);
}
return 1;
}
#------------------------------------------------------------------------------
# Extract information from an Ogg FLAC file
# Inputs: 0) ExifTool object reference, 1) dirInfo reference
# Returns: 1 on success, 0 if this wasn't a valid Ogg FLAC file
sub ProcessFLAC($$)
{
my ($exifTool, $dirInfo) = @_;
# must first check for leading/trailing ID3 information
unless ($exifTool->{DONE_ID3}) {
require Image::ExifTool::ID3;
Image::ExifTool::ID3::ProcessID3($exifTool, $dirInfo) and return 1;
}
my $raf = $$dirInfo{RAF};
my $verbose = $exifTool->Options('Verbose');
my $out = $exifTool->Options('TextOut');
my ($buff, $err);
# check FLAC signature
$raf->Read($buff, 4) == 4 and $buff eq 'fLaC' or return 0;
$exifTool->SetFileType() unless $exifTool->{VALUE}->{FileType};
SetByteOrder('MM');
my $tagTablePtr = GetTagTable('Image::ExifTool::FLAC::Main');
for (;;) {
# read next metadata block header
$raf->Read($buff, 4) == 4 or last;
my $flag = unpack('C', $buff);
my $size = unpack('N', $buff) & 0x00ffffff;
$raf->Read($buff, $size) == $size or $err = 1, last;
my $last = $flag & 0x80; # last-metadata-block flag
my $tag = $flag & 0x7f; # tag bits
if ($verbose) {
print $out "FLAC metadata block, type $tag:\n";
$exifTool->VerboseDump(\$buff, DataPos => $raf->Tell() - $size);
}
$exifTool->HandleTag($tagTablePtr, $tag, undef,
DataPt => \$buff,
DataPos => $raf->Tell() - $size,
);
last if $last; # all done if is set
}
$err and $exifTool->Warn('Format error in FLAC file');
return 1;
}
1; # end
__END__
=head1 NAME
Image::ExifTool::FLAC - Read Free Lossless Audio Codec information
=head1 SYNOPSIS
This module is used by Image::ExifTool
=head1 DESCRIPTION
This module contains definitions required by Image::ExifTool to extract meta
information from Free Lossless Audio Codec (FLAC) audio files.
=head1 AUTHOR
Copyright 2003-2008, Phil Harvey (phil at owl.phy.queensu.ca)
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
=head1 REFERENCES
=over 4
=item L
=back
=head1 SEE ALSO
L,
L
=cut