Apple Lossless
Apple Lossless, also known as Apple Lossless Audio Codec ( ALAC ) is an Apple -developed, free codec for lossless audio data compression. The compressed audio data is saved in MP4 files with the file extension. M4a or. Mp4. The method compresses the original on average about 60 percent of the original size. It offers no options or various modifications and needs relatively little computational effort for decoding.
With Apple's own iTunes software can thus compress (eg audio CDs ) linear PCM uncompressed material from WAV or AIFF files.
Apple Lossless is also used by Apple's AirPlay service uses, which is streaming music over Wi-Fi to other AirPlay -enabled devices. The Apple Lossless format can also be played by all multimedia devices from Apple, such as iPod, iPhone, iPad, or Apple TV.
Technology
It is based on linear prediction coding of the residual signal by Golomb -Rice codes. The bit stream is stored on a separate, non-standard extension in MP4 container format, because the process itself is not included or provided in the standard. ( The standard lossless audio codec in MPEG -4 standard is the MPEG -4. )
History
Apple Lossless was introduced as part of QuickTime 6.5.1 on 28 April 2004. The format can therefore be used by all applications that support QuickTime, such as Apple's iTunes 4.5 or later.
By reverse-engineering works of the Australian students and hacker David Hammerton is since March 5, 2005 code for a simple decoder in the C programming language available. It now created a program that can convert files in Apple Lossless format to WAV format.
As part of a Google Summer of Code project, Jai Menon implemented a free ( LGPL ) encoder for the format, which is included in the FFmpeg package since 20 August 2008.
Since October 2011, the Apple Lossless Audio Codec free software and is subject to the Apache License. With the release of the source code and the free utility ALAC may also be used for long-term archiving, then depending on the technical progress newer compressions can be exported in the lossless compressed from the original.
Supported Media Players
Hardware
- Apple iPad
- Apple iPhone
- Apple iPod
- Apple TV