A recent news came on the Mac OS forge that the Apple has made its Lossless Audio Codec (ALAC) open source. Basically, an ALAC is an audio codec developed by Apple and supported on iPhone, iPad, most iPods, Mac and iTunes.ALAC is a data compression method which reduces the size of audio files with no loss of information. A decoded ALAC stream is bit-for-bit identical to the original uncompressed audio file. This ALAC codecs are very much similar to other “lossless” codecs such as FLAC which offer audio compression without any loss in audio information. ALAC is said to compress files only by “about half” as compared to the originals.
How Apple’s Lossless Audio Codec Works ?
Apple Lossless data is stored within an MP4 container with the filename extension .m4a – this extension is also used by Apple for AAC audio data in an MP4 container (same container, different audio encoding). However, Apple Lossless is not a variant of AAC (which is a lossy format), but rather a distinct lossless format that uses linear prediction similar to other lossless codecs such as FLAC and Shorten. All current iPods and iPhones can play Apple Lossless–encoded files. It does not use any digital rights management (DRM) scheme, but by the nature of the container, it is thought that DRM could be applied to ALAC much the same way it can with other files in QuickTime containers.
The Apple Lossless Audio Codec project contains the sources for the ALAC encoder and decoder. Also included is an example command line utility, called alacconvert, to read and write audio data to/from Core Audio Format (CAF) and WAVE files. A description of a ‘magic cookie’ for use with files based on the ISO base media file format (e.g. MP4 and M4A) is included as well.
The Apple Lossless Audio Codec sources are available under the Apache license. Details can be found here http://www.apache.org/licenses/LICENSE-2.0.
{Via Wikipedia and 9to5Mac}
