NAME

NAME
Audio::Scan - Fast C metadata and tag reader for all common audio file
formats

SYNOPSIS
use Audio::Scan;

my $data = Audio::Scan->scan('/path/to/file.mp3');

# Just file info
my $info = Audio::Scan->scan_info('/path/to/file.mp3');

# Just tags
my $tags = Audio::Scan->scan_tags('/path/to/file.mp3');

# Scan without reading (possibly large) artwork into memory.
# Instead of binary artwork data, the size of the artwork will be returned instead.
{
local $ENV{AUDIO_SCAN_NO_ARTWORK} = 1;
my $data = Audio::Scan->scan('/path/to/file.mp3');
}

# Scan a filehandle
open my $fh, '<', 'my.mp3';
my $data = Audio::Scan->scan_fh( mp3 => $fh );
close $fh;

# Scan and compute an audio MD5 checksum
my $data = Audio::Scan->scan( '/path/to/file.mp3', { md5_size => 100 * 1024 } );
my $md5 = $data->{info}->{audio_md5};

DESCRIPTION
Audio::Scan is a C-based scanner for audio file metadata and tag
information. It currently supports MP3, MP4, Ogg Vorbis, FLAC, ASF, WAV,
AIFF, Musepack, Monkey's Audio, and WavPack.

See below for specific details about each file format.

METHODS
scan( $path, [ \%OPTIONS ] )
Scans $path for both metadata and tag information. The type of scan
performed is determined by the file's extension. Supported extensions
are:

MP3: mp3, mp2
MP4: mp4, m4a, m4b, m4p, m4v, m4r, k3g, skm, 3gp, 3g2, mov
AAC (ADTS): aac
Ogg: ogg, oga
FLAC: flc, flac, fla
ASF: wma, wmv, asf
Musepack: mpc, mpp, mp+
Monkey's Audio: ape, apl
WAV: wav
AIFF: aiff, aif
WavPack: wv

This method returns a hashref containing two other hashrefs: info and
tags. The contents of the info and tag hashes vary depending on file
format, see below for details.

An optional hashref may be provided. Currently this supports one item:

md5_size => $audio_bytes_to_checksum

An MD5 will be computed of the first N audio bytes. Any tags in the file
are automatically skipped, so this is a useful way of determining if a
file's audio content is the same even if tags may have been changed. The
hex MD5 value is returned in the $info->{audio_md5} key. This option
will reduce performance, so choose a small enough size that works for
you, you should probably avoid using more than 64K for example.

scan_info( $path, [ \%OPTIONS ] )
If you only need file metadata and don't care about tags, you can use
this method.

scan_tags( $path, [ \%OPTIONS ] )
If you only need the tags and don't care about the metadata, use this
method.

scan_fh( $type => $fh, [ \%OPTIONS ] )
Scans a filehandle. $type is the type of file to scan as, i.e. "mp3" or
"ogg". Note that FLAC does not support reading from a filehandle.

find_frame( $path, $timestamp_in_ms )
Returns the byte offset to the first audio frame starting from the given
timestamp (in milliseconds).

MP3, Ogg, FLAC, ASF, MP4
The byte offset to the data packet containing this timestamp will be
returned. For file formats that don't provide timestamp information
such as MP3, the best estimate for the location of the timestamp
will be returned. This will be more accurate if the file has a Xing
header or is CBR for example.

WAV, AIFF, Musepack, Monkey's Audio, WavPack
Not yet supported by find_frame.

find_frame_return_info( $mp4_path, $timestamp_in_ms )
The header of an MP4 file contains various metadata that refers to the
structure of the audio data, making seeking more difficult to perform.
This method will return the usual $info hash with 2 additional keys:

seek_offset - The seek offset in bytes
seek_header - A rewritten MP4 header that can be prepended to the audio data
found at seek_offset to construct a valid bitstream. Specifically,
the following boxes are rewritten: stts, stsc, stsz, stco

For example, to seek 30 seconds into a file and write out a new MP4 file
seeked to this point:

my $info = Audio::Scan->find_frame_return_info( $file, 30000 );

open my $f, '<', $file;
sysseek $f, $info->{seek_offset}, 1;

open my $fh, '>', 'seeked.m4a';
print $fh $info->{seek_header};

while ( sysread( $f, my $buf, 65536 ) ) {
print $fh $buf;
}

close $f;
close $fh;

find_frame_fh( $type => $fh, $offset )
Same as "find_frame", but with a filehandle.

find_frame_fh_return_info( $type => $fh, $offset )
Same as "find_frame_return_info", but with a filehandle.

has_flac()
Deprecated. Always returns 1 now that FLAC is always enabled.

is_supported( $path )
Returns 1 if the given path can be scanned by Audio::Scan, or 0 if not.

get_types()
Returns an array of strings of the file types supported by Audio::Scan.

extensions_for( $type )
Returns an array of strings of the file extensions that are considered
to be the file type *$type*.

type_for( $extension )
Returns file type for a given extension. Returns *undef* for unsupported
extensions.

MP3
INFO
The following metadata about a file may be returned:

id3_version (i.e. "ID3v2.4.0")
song_length_ms (duration in milliseconds)
layer (i.e. 3)
stereo
samples_per_frame
padding
audio_size (size of all audio frames)
audio_offset (byte offset to first audio frame)
bitrate (in bps, determined using Xing/LAME/VBRI if possible, or average in the worst case)
samplerate (in kHz)
vbr (1 if file is VBR)

If a Xing header is found:
xing_frames
xing_bytes
xing_quality

If a VBRI header is found:
vbri_delay
vbri_frames
vbri_bytes
vbri_quality

If a LAME header is found:
lame_encoder_version
lame_tag_revision
lame_vbr_method
lame_lowpass
lame_replay_gain_radio
lame_replay_gain_audiophile
lame_encoder_delay
lame_encoder_padding
lame_noise_shaping
lame_stereo_mode
lame_unwise_settings
lame_source_freq
lame_surround
lame_preset

TAGS
Raw tags are returned as found. This means older tags such as ID3v1 and
ID3v2.2/v2.3 are converted to ID3v2.4 tag names. Multiple instances of a
tag in a file will be returned as arrays. Complex tags such as APIC and
COMM are returned as arrays. All tag fields are converted to upper-case.
All text is converted to UTF-8.

Sample tag data:

tags => {
ALBUMARTISTSORT => "Solar Fields",
APIC => [ "image/jpeg", 3, "", <binary data snipped> ],
CATALOGNUMBER => "INRE 017",
COMM => ["eng", "", "Amazon.com Song ID: 202981429"],
"MUSICBRAINZ ALBUM ARTIST ID" => "a2af1f31-c9eb-4fff-990c-c4f547a11b75",
"MUSICBRAINZ ALBUM ID" => "282143c9-6191-474d-a31a-1117b8c88cc0",
"MUSICBRAINZ ALBUM RELEASE COUNTRY" => "FR",
"MUSICBRAINZ ALBUM STATUS" => "official",
"MUSICBRAINZ ALBUM TYPE" => "album",
"MUSICBRAINZ ARTIST ID" => "a2af1f31-c9eb-4fff-990c-c4f547a11b75",
"REPLAYGAIN_ALBUM_GAIN" => "-2.96 dB",
"REPLAYGAIN_ALBUM_PEAK" => "1.045736",
"REPLAYGAIN_TRACK_GAIN" => "+3.60 dB",
"REPLAYGAIN_TRACK_PEAK" => "0.892606",
TALB => "Leaving Home",
TCOM => "Magnus Birgersson",
TCON => "Ambient",
TCOP => "2005 ULTIMAE RECORDS",
TDRC => "2004-10",
TIT2 => "Home",
TPE1 => "Solar Fields",
TPE2 => "Solar Fields",
TPOS => "1/1",
TPUB => "Ultimae Records",
TRCK => "1/11",
TSOP => "Solar Fields",
UFID => [
"http://musicbrainz.org",
"1084278a-2254-4613-a03c-9fed7a8937ca",
],
},

MP4
INFO
The following metadata about a file may be returned:

audio_offset (byte offset to start of mdat)
audio_size
compatible_brands
file_size
leading_mdat (if file has mdat before moov)
major_brand
minor_version
song_length_ms
timescale
tracks (array of tracks in the file)
Each track may contain:

audio_type
avg_bitrate
bits_per_sample
channels
duration
encoding
handler_name
handler_type
id
max_bitrate
samplerate

TAGS
Tags are returned in a hash with all keys converted to upper-case. Keys
starting with 0xA9 (copyright symbol) will have this character stripped
out. Sample tag data:

tags => {
AART => "Album Artist",
ALB => "Album",
ART => "Artist",
CMT => "Comments",
COVR => <binary data snipped>,
CPIL => 1,
DAY => 2009,
DESC => "Video Description",
DISK => "1/2",
"ENCODING PARAMS" => "vers\0\0\0\1acbf\0\0\0\2brat\0\1w\0cdcv\0\1\6\5",
GNRE => "Jazz",
GRP => "Grouping",
ITUNNORM => " 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000",
ITUNSMPB => " 00000000 00000840 000001E4 00000000000001DC 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000",
LYR => "Lyrics",
NAM => "Name",
PGAP => 1,
SOAA => "Sort Album Artist",
SOAL => "Sort Album",
SOAR => "Sort Artist",
SOCO => "Sort Composer",
SONM => "Sort Name",
SOSN => "Sort Show",
TMPO => 120,
TOO => "iTunes 8.1.1, QuickTime 7.6",
TRKN => "1/10",
TVEN => "Episode ID",
TVES => 12,
TVSH => "Show",
TVSN => 12,
WRT => "Composer",
},

AAC (ADTS)
INFO
The following metadata about a file is returned:

audio_offset
audio_size
bitrate (in bps)
channels
file_size
profile (Main, LC, or SSR)
samplerate (in kHz)
song_length_ms (duration in milliseconds)

OGG VORBIS
INFO
The following metadata about a file is returned:

version
channels
stereo
samplerate (in kHz)
bitrate_average (in bps)
bitrate_upper
bitrate_nominal
bitrate_lower
blocksize_0
blocksize_1
audio_offset (byte offset to audio)
audio_size
song_length_ms (duration in milliseconds)

TAGS
Raw Vorbis comments are returned. All comment keys are capitalized.

FLAC
INFO
The following metadata about a file is returned:

channels
samplerate (in kHz)
bitrate (in bps)
file_size
audio_offset (byte offset to first audio frame)
audio_size
song_length_ms (duration in milliseconds)
bits_per_sample
frames
minimum_blocksize
maximum_blocksize
minimum_framesize
maximum_framesize
md5
total_samples

TAGS
Raw FLAC comments are returned. All comment keys are capitalized. Some
data returned is special:

APPLICATION

Each application block is returned in the APPLICATION tag keyed by application ID.

CUESHEET_BLOCK

The CUESHEET_BLOCK tag is an array containing each line of the cue sheet.

ALLPICTURES

Embedded pictures are returned in an ALLPICTURES array. Each picture has the following metadata:

mime_type
description
width
height
depth
color_index
image_data
picture_type

ASF (Windows Media Audio/Video)
INFO
The following metadata about a file may be returned. Reading the ASF
spec is encouraged if you want to find out more about any of these
values.

audio_offset (byte offset to first data packet)
audio_size
broadcast (boolean, whether the file is a live broadcast or not)
codec_list (array of information about codecs used in the file)
creation_date (UNIX timestamp when file was created)
data_packets
drm_key
drm_license_url
drm_protection_type
drm_data
file_id (unique file ID)
file_size
index_blocks
index_entry_interval (in milliseconds)
index_offsets (byte offsets for each second of audio, per stream. Useful for seeking)
index_specifiers (indicates which stream a given index_offset points to)
language_list (array of languages referenced by the file's metadata)
lossless (boolean)
max_bitrate
max_packet_size
min_packet_size
mutex_list (mutually exclusive stream information)
play_duration_ms
preroll
script_commands
script_types
seekable (boolean, whether the file is seekable or not)
send_duration_ms
song_length_ms (the actual length of the audio, in milliseconds)

STREAMS

The streams array contains metadata related to an individul stream
within the file. The following metadata may be returned:

DeviceConformanceTemplate
IsVBR
alt_bitrate
alt_buffer_fullness
alt_buffer_size
avg_bitrate (most accurate bitrate for this stream)
avg_bytes_per_sec (audio only)
bitrate
bits_per_sample (audio only)
block_alignment (audio only)
bpp (video only)
buffer_fullness
buffer_size
channels (audio only)
codec_id (audio only)
compression_id (video only)
encode_options
encrypted (boolean)
error_correction_type
flag_seekable (boolean)
height (video only)
index_type
language_index (offset into language_list array)
max_object_size
samplerate (in kHz) (audio only)
samples_per_block
stream_number
stream_type
super_block_align
time_offset
width (video only)

TAGS
Raw tags are returned. Tags that occur more than once are returned as
arrays. In contrast to the other formats, tag keys are NOT capitalized.
There is one special key:

WM/Picture

Pictures are returned as a hash with the following keys:

image_type (numeric type, same as ID3v2 APIC)
mime_type
description
image

WAV
INFO
The following metadata about a file may be returned.

audio_offset
audio_size
bitrate (in bps)
bits_per_sample
block_align
channels
file_size
format (WAV format code, 1 == PCM)
id3_version (if an ID3v2 tag is found)
samplerate (in kHz)
song_length_ms

TAGS
WAV files can contain several different types of tags. "Native" WAV tags
found in a LIST block may include these and others:

IARL - Archival Location
IART - Artist
ICMS - Commissioned
ICMT - Comment
ICOP - Copyright
ICRD - Creation Date
ICRP - Cropped
IENG - Engineer
IGNR - Genre
IKEY - Keywords
IMED - Medium
INAM - Name (Title)
IPRD - Product (Album)
ISBJ - Subject
ISFT - Software
ISRC - Source
ISRF - Source Form
TORG - Label
LOCA - Location
TVER - Version
TURL - URL
TLEN - Length
ITCH - Technician
TRCK - Track
ITRK - Track

ID3v2 tags can also be embedded within WAV files. These are returned
exactly as for MP3 files.

AIFF
INFO
The following metadata about a file may be returned.

audio_offset
audio_size
bitrate (in bps)
bits_per_sample
block_align
channels
compression_name (if AIFC)
compression_type (if AIFC)
file_size
id3_version (if an ID3v2 tag is found)
samplerate (in kHz)
song_length_ms

TAGS
ID3v2 tags can be embedded within AIFF files. These are returned exactly
as for MP3 files.

MONKEY'S AUDIO (APE)
INFO
The following metadata about a file may be returned.

audio_offset
audio_size
bitrate (in bps)
channels
compression
file_size
samplerate (in kHz)
song_length_ms
version

TAGS
APEv2 tags are returned as a hash of key/value pairs.

MUSEPACK
INFO
The following metadata about a file may be returned.

audio_offset
audio_size
bitrate (in bps)
channels
encoder
file_size
profile
samplerate (in kHz)
song_length_ms

TAGS
Musepack uses APEv2 tags. They are returned as a hash of key/value
pairs.

WAVPACK

The following metadata about a file may be returned.

audio_offset
audio_size
bitrate (in bps)
bits_per_sample
channels
encoder_version
file_size
hybrid (1 if file is lossy) (v4 only)
lossless (1 if file is lossless) (v4 only)
samplerate
song_length_ms
total_samples

TAGS
WavPack uses APEv2 tags. They are returned as a hash of key/value pairs.

THANKS
Some code from the Rockbox project was very helpful in implementing ASF
and MP4 seeking.

Some of the file format parsing code was derived from the mt-daapd
project, and adapted by Netgear. It has been heavily rewritten to fix
bugs and add more features.

The source to the original Netgear C scanner for SqueezeCenter is
located at
<http://svn.slimdevices.com/repos/slim/7.3/trunk/platforms/readynas/cont
rib/scanner>

The audio MD5 feature uses an MD5 implementation by L. Peter Deutsch,
<[email protected]>.

SEE ALSO
ASF Spec
<http://www.microsoft.com/windows/windowsmedia/forpros/format/asfspec.as
px>

MP4 Info:
<http://standards.iso.org/ittf/PubliclyAvailableStandards/c051533_ISO_IE
C_14496-12_2008.zip>
<http://www.geocities.com/xhelmboyx/quicktime/formats/mp4-layout.txt>

AUTHORS
Andy Grundman, <[email protected]>

Dan Sully, <[email protected]>

COPYRIGHT AND LICENSE
Copyright (C) 2010 Logitech, Inc.

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.