Apple Lossless

Infobox file format
name = Apple Lossless
logo =


caption =
extension = .m4a
mime =
type code =
uniform type =
magic =
owner = Apple Inc.
type = Lossless audio file format
container for =
contained by = MPEG-4 Part 14
extended from =
extended to =
standard =

Apple Lossless (also known as Apple Lossless Encoder, ALE, or Apple Lossless Audio Codec, ALAC) is an audio codec developed by Apple Inc. for lossless data compression of digital music.

Apple Lossless data is stored within an MP4 container with the filename extension ".m4a". It is not a variant of AAC, but uses linear prediction similar to other lossless codecs such as FLAC and Shorten. [cite web | url=http://article.gmane.org/gmane.comp.video.ffmpeg.devel/19686 | title=Re: Apple Lossless Audio Codec: Issues surrounding the release of my code? | accessdate=2006-11-05 | first=David | last=Hammerton | date=2005-03-01 | publisher=Gmane] iPods with a dock connector (not the Shuffle) and recent firmware can play Apple Lossless-encoded files. It does not utilize any digital rights management (DRM) scheme, but by the nature of the container, it is thought that DRM can be applied to ALAC much the same way it can with other files in QuickTime containers.

Apple claims that audio files compressed with its lossless codec will use up "about half the storage space" that the uncompressed data would require. Testers using a selection of music have found that compressed files are about 40% to 60% the size of the originals depending on the kind of music, similar to other lossless formats. Furthermore, the speed at which it can be decoded makes it useful for a limited-power device such as the iPod. [cite web | url=http://members.home.nl/w.speek/comparison.htm | title=Performance comparison of lossless audio compressors | accessdate=2006-11-05 | date=2005-02-07 | author=Speek]

The Apple Lossless Encoder was introduced as a component of QuickTime 6.5.1 on April 28, 2004 and thus as a feature of iTunes 4.5. The codec is also used in the AirPort Express's AirTunes implementation.

Alternate players

David Hammerton and Cody Brocious have analyzed and decoded this codec without any documents on the format. On March 5, 2005 Hammerton published a simple open source decoder in the programming language C on the basis of the reverse engineering work.

The open source library libavcodec now incorporates both a decoder and an encoder for Apple Lossless format which means that media players based on that library, including VLC media player and MPlayer, are able to play Apple Lossless files.

Notes

See also

Other comparable lossless audio codecs:
* TTA
* FLAC
* Monkey's Audio
* Shorten
* WavPack
* WMA Lossless
* Comparison of audio codecs

External links

* [http://www.apple.com/itunes/features/#importing Apple - iTunes - Import]
* [http://craz.net/programs/itunes/alac.html Open Source Decoder]
* [http://www.hydrogenaudio.org/forums/index.php?showtopic=32111 Win32 port of the Open Source ALAC Decoder]
* [http://members.home.nl/w.speek/comparison.htm Comparison of lossless codecs]