Apple Lossless

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Logo of the open source audio format Apple Lossless

Apple Lossless , also known as Apple Lossless Audio Codec ( ALAC ), is a free codec developed by Apple for lossless audio data compression . The compressed audio data are saved in MP4 files with the file extension .m4a or .mp4 . The process compresses the original to an average of around 60 percent of the original size. It does not offer any options or various modifications and requires relatively little computing effort for decoding.

Apple's own iTunes software can be used to compress uncompressed linear PCM material from WAV or AIFF files (e.g. from audio CDs ).

Apple Lossless is also used by Apple's AirPlay service, which streams music to other AirPlay-enabled devices over WiFi . The Apple Lossless format can also be played by all multimedia devices from Apple, such as iPod , iPhone , iPad or Apple TV .


It is based on linear prediction with coding of the residual signal using Golomb-Rice codes . The bit stream is saved via its own, non-standardized extension in the MP4 container format, since the process itself is not included or intended in the standard. (The standardized lossless audio codec in the MPEG-4 standard is MPEG-4 ALS .)


Apple Lossless was introduced as part of QuickTime 6.5.1 on April 28, 2004 . The format can therefore be used by all programs that support Quicktime, for example Apple's iTunes from version 4.5.

As a result of reverse engineering work by the Australian student and hacker David Hammerton, code for a simple decoder in the C programming language has been available since March 5, 2005 . This has meanwhile resulted in a program that can convert files in Apple Lossless format into WAV format .

As part of a Google Summer of Code project, Jai Menon implemented a free (under LGPL ) encoder for the format, which has been included in the FFmpeg package since August 20, 2008 .

The Apple Lossless Audio Codec has been free software since October 2011 and is subject to the Apache license . With the publication of the source code and its free usability, ALAC can also be used for long-term archiving, in which the losslessly compressed original can then be exported, depending on technical progress, newer compressions.

Supported media players



See also

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