Apple Lossless
From Free net encyclopedia
Image:ITunes-mpeg4.png Apple Lossless (also known as Apple Lossless Encoder, ALE, or Apple Lossless Audio Codec, ALAC) is an audio codec developed by Apple Computer for lossless compression of digital music.
Apple Lossless data is stored within an MP4 container with the filename extension .m4a. While Apple Lossless has the same file extension as AAC, it is not a variant of AAC but instead uses linear prediction [1] similar to other lossless codecs such as FLAC and Shorten. iPods with a dock connector 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 60% the size of the originals, similar to other lossless formats. Compared to most other formats, Apple Lossless is not as difficult to decode, making it practical for a limited-power device such as an iPod.
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.
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.
See also
Other comparable lossless audio codecs:
External links
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