Apple Lossless, also known as the Apple Lossless Audio Codec (ALAC), or Apple Lossless Encoder (ALE), is an audio coding format, and its implementation of audio codec reference, developed by Apple Inc. for data lossless compression of data. digital music. After initially retaining ownership since its inception in 2004, Apple made the codec available at the end of 2011 and royalty-free. Traditionally, Apple has called the Apple Lossless codec, although more recently it has started using the abbreviated term ALAC with reference to the codec.
Apple Lossless supports up to 8 16, 20, 24 and 32 bit audio channels with a maximum sample rate of 384 kHz. Apple Lossless data is frequently stored in an MP4 container with the .m4a file name extension. This extension is also used by Apple for lossy 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 lossless, distinct format that uses linear prediction similar to other lossless codecs. These other lossless codecs, such as FLAC and Shorten, are not natively supported by Apple’s iTunes software (Mac OS or Windows versions) or older iOS devices. More modern devices such as the iPhone 7 and higher, running iOS11, support FLAC playback. ITunes users who want to use a lossless format that allows the addition of metadata (unlike WAV / AIFF or other PCM formats, where metadata is usually ignored) must use ALAC. All current iOS devices can read ALAC encoded files. The ALAC does not use a DRM system either; but by the nature of the MP4 container, it is possible that DRM can be applied to the ALAC in the same way that it is applied to files in other QuickTime containers. According to Apple, audio files compressed with its lossless codec will use “about half of the storage space” that uncompressed data would require. Testers using a music selection found that compressed files accounted for about 40% to 60% of the size of originals, depending on the type of music, which is similar to other lossless formats. In addition, compared to other formats, it is not as difficult to decode, which makes it convenient for a limited-power device, such as older iOS devices. Partly because of the use of an MP4 container, Apple Lossless does not contain built-in error control. Although it is not as common, the ALAC format can also use the .CAF file type container.
The ALAC file encoding software, Apple Lossless Encoder, was introduced in the Mac OS X Core Audio framework on April 28, 2004 with the update of QuickTime 6.5.1; making it available in iTunes since version 4.5 and up. The codec is also used in AirPort and AirPlay implementations. The Apple Lossless encoder (and decoder) was released as free software under Apache license version 2.0 on October 27, 2011, but an open source, reverse-source, open source encoder and decoder was already available before publication.
David Hammerton and Cody Brocious analyzed and decoded this codec without any document on the format. On March 5, 2005, Hammerton released a simple open source decoder in the C programming language based on reverse engineering work. The libavcodec open source library incorporates both a decoder and an encoder for the Apple Lossless format, which means that (including VLC media player and MPlayer, as well as many multimedia applications for home theater, such as Plex, XBMC and Boxee) able to read Apple Lossless files. The library was then optimized for ARM processors and included in Rockbox. Foobar2000 will also play Apple Lossless files just like JRiver Media Center and BitPerfect.