Apple Lossless Audio Codec
|Initial release||April 28, 2004|
October 28, 2011
|License||Apache License 2.0|
|Developed by||Apple Inc.|
|Type of format||Lossless audio|
|Contained by||MPEG-4 Part 14|
The Apple Lossless Audio Codec (ALAC), also known as Apple Lossless, or Apple Lossless Encoder (ALE), is an audio coding format, and its reference audio codec implementation, developed by Apple Inc. for lossless data compression of digital music. After initially keeping it proprietary from its inception in 2004, in late 2011 Apple made the codec available open source and royalty-free. Traditionally, Apple has referred to the codec as Apple Lossless, though more recently it has begun to use the abbreviated term ALAC when referring to the codec.
ALAC supports up to 8 channels of audio at 16, 20, 24 and 32 bit depth with a maximum sample rate of 384 kHz.
ALAC data is frequently stored within an MP4 container with the filename extension .m4a. This extension is also used by Apple for lossy AAC audio data in an MP4 container (same container, different audio encoding). The codec can also be used by the .CAF file type container, though this is much less common.
ALAC also does not use any DRM scheme;[dubious ] but by the nature of the MP4 container, it is feasible that DRM could be applied to ALAC much in the same way it is applied to files in other QuickTime containers.
According to Apple, 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, which is similar to other lossless formats.
ALAC has been measured to require around four times as much CPU power to decode than FLAC does, with implications for battery life on limited-power devices. Still the format has been recommended for older iPod devices based on claims of lower power usage.
Partly because of the use of an MP4 container, ALAC does not contain integrated error checking.
The data compression software for encoding into ALAC files, Apple Lossless Encoder, was introduced into the Mac OS X Core Audio framework on April 28, 2004, together with the QuickTime 6.5.1 update, thus making it available in iTunes since version 4.5 and above, and its replacement, the Music application. The codec is also used in the AirPort and AirPlay implementation.
David Hammerton and Cody Brocious analyzed and reverse engineered the codec without any documents on the format. On March 5, 2005, Hammerton published a simple open source decoder written in the C programming language on the basis of the work.
Apple support for lossless formats
Other lossless codecs, such as FLAC and Shorten, are not natively supported by Apple's iTunes nor the later Music app (either the macOS or Windows versions) or by iOS devices running iOS 10 or below. In order to be played through the iTunes and Music app on iOS, audio files using these lossless codecs may be converted via various third-party tools into ALAC-encoded files with no change in fidelity.
Third-party applications are available from the App Store to play such files without converting them. Devices running iOS 11 or above do support FLAC playback natively, through the Files application only. The method of importing the files to the Apple device varies between applications, including Files, as there is currently no official support for doing so.
All current iOS devices can play ALAC encoded files.
The open source library libavcodec incorporates both a decoder and an encoder for the ALAC format, which means that media players based on that library (including VLC media player and MPlayer, as well as many media center applications for home theater computers, such as Plex, XBMC, and Boxee) are able to play ALAC files.
As of 2015, Windows 10 includes support for ALAC encoding and decoding, thereby enabling other media players to use it, e.g. Windows Media Player when ripping CDs or the Spotify desktop client for playback of local .m4a files.
- Audio Interchange File Format (AIFF)
- Comparison of audio coding formats
- Free Lossless Audio Codec (FLAC)
- Monkey's Audio
- Windows Media Audio 9 Lossless
- "Subscribe to iTunes Match". Apple Inc. May 8, 2017. Retrieved May 31, 2017.
If you have songs encoded in ALAC, WAV, or AIFF formats, we create an AAC 256Kbps version and upload it to iCloud so that it can be played on all of your other devices.
- "Access your music collection on all of your devices with Apple Music". Apple Inc. May 12, 2017. Retrieved May 31, 2017.
We create AAC 256Kbps versions of songs that are encoded in ALAC, WAV, or AIFF formats and add the AAC version to iCloud Music Library.
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- "Apple Music announces Spatial Audio and Lossless Audio". Apple Newsroom.
Apple Music will also make its catalog of more than 75 million songs available in Lossless Audio. Apple uses ALAC (Apple Lossless Audio Codec) to preserve every single bit of the original audio file. This means Apple Music subscribers will be able to hear the exact same thing that the artists created in the studio.
- "iOS 11 lets you play FLAC audio files straight from your iPad and iPhone". The Next Web. June 6, 2017. Retrieved August 25, 2020.
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- "Apple Music announces Spatial Audio and Lossless Audio". Apple Newsroom. Retrieved 17 May 2021.
- ALAC Project at MacOSForge
- ALAC technical features at MacOSForge
- ALAC importing at Apple
- ALAC compression rates for different types of music article by Kirk McElhern