Apple Lossless
Encyclopedia
Apple Lossless
Apple Lossless (also known as ALAC (Apple Lossless Audio Codec), or ALE (Apple Lossless Encoder) is an audio codec
developed by Apple Inc. for lossless data compression
of digital music
. After initially being proprietary for many years, in late 2011 Apple open sourced
and royalty-freed the Apple Lossless codec. It is worth noting that Apple does not use the ALAC abbreviation, always using the name Apple Lossless when presenting or discussing this codec, but it is more commonly referred to as ALAC outside of Apple.
.m4a. This extension is also used by Apple for lossy AAC audio data in an MP4 container (same container, different audio encoding), though lossy AAC files, as sold through the iTunes Store
, are typically in their own .aac container extension. 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. These other lossless codecs, such as FLAC and Shorten
, are not natively supported in Apple's iTunes software, either on computers (Mac or Windows) or iDevices, so users of iTunes software who want to use a lossless format (which allows the addition of metadata; unlike WAV/AIF and other PCM-type formats) have to use ALAC. All current iDevices can play ALAC–encoded files. ALAC also does not use any DRM
scheme, but by the nature of the MP4 container, it is thought that DRM could be applied to ALAC much the same way it can with files in other 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 limited-power devices such as iDevices.
framework on April 28, 2004 together with the QuickTime
6.5.1 update, and thus available in iTunes
as of version 4.5 and above. The codec is also used in the AirPort Express
's AirPlay
implementation.
The Apple Lossless Encoder (and decoder) was released as open source software under the Apache License
version 2.0 on October 27, 2011.
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
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, as well as many media centre applications for home theatre computer
s, such as Plex, XBMC, and Boxee
. The library was subsequently optimized for ARM processors and included in Rockbox
.
Apple Lossless (also known as ALAC (Apple Lossless Audio Codec), or ALE (Apple Lossless Encoder) is an audio codec
Audio codec
All codecs are devices or computer programs capable of coding or decoding a digital data stream or signal.The term audio codec has two meanings depending on the context:...
developed by Apple Inc. for lossless data compression
Lossless data compression
Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. The term lossless is in contrast to lossy data compression, which only allows an approximation of the original data to be reconstructed, in exchange...
of digital music
Music
Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...
. After initially being proprietary for many years, in late 2011 Apple open sourced
Open-source software
Open-source software is computer software that is available in source code form: the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, improve and at times also to distribute the software.Open...
and royalty-freed the Apple Lossless codec. It is worth noting that Apple does not use the ALAC abbreviation, always using the name Apple Lossless when presenting or discussing this codec, but it is more commonly referred to as ALAC outside of Apple.
Codec
Apple Lossless data is stored within an MP4 container with the filename extensionFilename extension
A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
.m4a. This extension is also used by Apple for lossy AAC audio data in an MP4 container (same container, different audio encoding), though lossy AAC files, as sold through the iTunes Store
ITunes Store
The iTunes Store is a software-based online digital media store operated by Apple. Opening as the iTunes Music Store on April 28, 2003, with over 200,000 items to purchase, it is, as of April 2008, the number-one music vendor in the United States...
, are typically in their own .aac container extension. However, Apple Lossless is not a variant of AAC
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
(which is a lossy format), but rather a distinct lossless format that uses linear prediction
Linear prediction
Linear prediction is a mathematical operation where future values of a discrete-time signal are estimated as a linear function of previous samples....
similar to other lossless codecs. These other lossless codecs, such as FLAC and Shorten
Shorten
Shorten is a file format used for compressing audio data. It is a form of data compression of files and is used to losslessly compress CD-quality audio files . Shorten is no longer developed and more recent lossless audio codecs such as FLAC, Monkey's Audio , TTA, and WavPack have become more...
, are not natively supported in Apple's iTunes software, either on computers (Mac or Windows) or iDevices, so users of iTunes software who want to use a lossless format (which allows the addition of metadata; unlike WAV/AIF and other PCM-type formats) have to use ALAC. All current iDevices can play ALAC–encoded files. ALAC also does not use any DRM
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
scheme, but by the nature of the MP4 container, it is thought that DRM could be applied to ALAC much the same way it can with files in other 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 limited-power devices such as iDevices.
History
The Apple Lossless Encoder (the software for encoding into ALAC files) was introduced into the Mac OS X Core AudioCore Audio
Core Audio is a low-level API for dealing with sound in Apple's Mac OS X and iOS operating systems. It includes an implementation of the cross-platform OpenAL library....
framework on April 28, 2004 together with the QuickTime
QuickTime
QuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...
6.5.1 update, and thus available in iTunes
ITunes
iTunes is a media player computer program, used for playing, downloading, and organizing digital music and video files on desktop computers. It can also manage contents on iPod, iPhone, iPod Touch and iPad....
as of version 4.5 and above. The codec is also used in the AirPort Express
AirPort
AirPort and AirPort Extreme are local area wireless networking products from Apple Inc. based on the IEEE 802.11 standard ....
's AirPlay
AirPlay
AirPlay is a proprietary protocol stack/suite developed by Apple Inc. that allows wireless streaming of audio, video, and photos, together with related metadata between devices...
implementation.
The Apple Lossless Encoder (and decoder) was released as open source software under the Apache License
Apache License
The Apache License is a copyfree free software license authored by the Apache Software Foundation . The Apache License requires preservation of the copyright notice and disclaimer....
version 2.0 on October 27, 2011.
Other players
David Hammerton and Cody BrociousCody Brocious
-Biography:Cody William Brocious was born in Waukegan, Illinois, the son of a Naval Drug and Alcohol counselor. He moved to Chambersburg, Pennsylvania at the age of 3 and became interested in computing by the age of 4...
have analyzed and decoded this codec without any documents on the format. On March 5, 2005, Hammerton published a simple open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
decoder in the programming language C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
on the basis of the reverse engineering
Reverse engineering
Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation...
work.
The open source library libavcodec
Libavcodec
libavcodec is a free software/open source LGPL-licensed library of codecs for encoding and decoding video and audio data. Same name but incompatible libraries are provided from both FFmpeg project and Libav project....
incorporates both a decoder and an encoder for Apple Lossless format which means that media players based on that library, including VLC media player
VLC media player
VLC media player is a free and open source media player and multimedia framework written by the VideoLAN project.VLC is a portable multimedia player, encoder, and streamer supporting many audio and video codecs and file formats as well as DVDs, VCDs, and various streaming protocols. It is able to...
and MPlayer
MPlayer
MPlayer is a free and open source media player. The program is available for all major operating systems, including Linux and other Unix-like systems, Microsoft Windows and Mac OS X. Versions for OS/2, Syllable, AmigaOS and MorphOS are also available. The Windows version works, with some minor...
, are able to play Apple Lossless files, as well as many media centre applications for home theatre computer
Home theater PC
A Home Theater PC or Media Center appliance is a convergence device that combines some or all the capabilities of a personal computer with a software application that supports video, photo, music playback, and sometimes video recording functionality...
s, such as Plex, XBMC, and Boxee
BOXEE
Boxee is a cross-platform freeware HTPC software application with a 10-foot user interface and social networking features designed for the living-room TV...
. The library was subsequently optimized for ARM processors and included in Rockbox
Rockbox
Rockbox is a replacement for the standard firmware in various forms of digital audio players . It offers an alternative to the player's operating system, in many cases without removing the original firmware, which provides a plug-in architecture for adding various enhancements and functions...
.
See also
- Comparison of audio codecsComparison of audio codecsThe following tables compare general and technical information for a variety of audio formats and audio compression formats. For listening tests comparing the perceived audio quality of audio formats and codecs, see the article Codec listening test....
- FLAC
- Monkey's AudioMonkey's AudioMonkey's Audio is a file format for audio data compression. Being a lossless format, Monkey's Audio does not discard data during the process of encoding, unlike lossy compression methods such as AAC, MP3, Vorbis and Musepack....
- TTATTA (codec)True Audio is a free software, real-time lossless audio codec, based on adaptive prognostic filters.Also, .tta is the generic extension to filenames of audio files created by True Audio codec.- Codec overview :...
- WavPackWavPackWavPack is a free, open source lossless audio compression format developed by David Bryant.-Features:WavPack compression can compress 8-, 16-, 24-, and 32-bit fixed-point, and 32-bit floating point audio files in the .WAV file format. It also supports surround sound streams and high frequency...
- WMA LosslessWindows Media Audio 9 LosslessWindows Media Audio 9 Lossless is a lossless audio codec by Microsoft, released in early 2003.It compresses an audio CD to a range of 206 to 411MB, at bit rates of 470 to 940 kbit/s. The result is a bit-for-bit duplicate of the original audio file; in other words, the audio quality on the CD will...