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.m4a: An audio-only MPEG-4 file, used by Apple for unprotected music downloaded from their iTunes Music Store. Audio within the m4a file is typically encoded with AAC, although lossless ALAC may also be used. .m4b: An Audiobook / podcast extension with AAC or ALAC encoded audio in an MPEG-4 container. Both M4A and M4B formats can contain ...
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 'Music' category is merely a guideline on commercialized uses of a particular format, not a technical assessment of its capabilities. For example, MP3 and AAC dominate the personal audio market in terms of market share, though many other formats are comparably well suited to fill this role from a purely technical standpoint.
A lossless audio coding format reduces the total data needed to represent a sound but can be de-coded to its original, uncompressed form. A lossy audio coding format additionally reduces the bit resolution of the sound on top of compression, which results in far less data at the cost of irretrievably lost information.
Audio-only MPEG-4 files generally have a .m4a extension. This is especially true of unprotected content. MPEG-4 files with audio streams encrypted by FairPlay digital rights management as were sold through the iTunes Store use the .m4p extension. iTunes Plus tracks, that the iTunes Store currently sells, are unencrypted and use .m4a accordingly.
TTA – Lossless compression; WavPack – Hybrid lossy/lossless; Bonk – Hybrid lossy/lossless; supported by fre:ac (formerly BonkEnc) Apple Lossless – Lossless compression (MP4) Fraunhofer FDK AAC – Lossy compression (AAC) FFmpeg codecs in the libavcodec library, e.g. AC-3, AAC, ADPCM, PCM, Apple Lossless, FLAC, WMA, Vorbis, MP2, etc.
This category contains audio compression codecs that yield lossless data compression. Pages in category "Lossless audio codecs"
Android 2.3 [67] and later supports AAC-LC, HE-AAC and HE-AAC v2 in MP4 or M4A containers along with several other audio formats. Android 3.1 and later supports raw ADTS files. Android 4.1 can encode AAC. [68] WebOS by HP/Palm supports AAC, AAC+, eAAC+, and .m4a containers in its native music player as well as several third-party players ...