[[File:Opus quality comparison colorblind compatible.svg|thumb|Comparison of coding efficiency between popular audio formats]]
An '''audio coding format'''<ref>The term "audio coding" can hebe seen in e.g. the name [[Advanced Audio Coding]], and is analogous to the term [[video coding format|video coding]]</ref> (or sometimes '''audio compression format''') is a [[Content format|content representation format]] for storage or transmission of [[Digital data|digital]] [[sound]] (such as in a video file, a sound file, or a [[Bitstream format|bitstream]]). Examples of audio coding formats include [[MP3]], [[Advanced Audio Coding|AAC]], [[Vorbis]], [[FLAC]], and [[Opus (audio format)|Opus]]. A specific software or hardware implementation capable of [[Data_compression#Audio|audio compression]] and/or decompression to/from a specific audio coding format is called aan [[audio codec]]; an example of an audio codec is [[LAME]], which is one of several different codecs which implements encoding and decoding audio in the [[MP3]] audio coding format in software.
Some audio coding formats are documented by a detailed [[technical specification]] document known as aan '''audio coding specification'''. Some such specifications are written and approved by [[standardization organization]]s as [[technical standard]]s, and are thus known as aan '''audio coding standard'''. The term 'standard' is also sometimes used for [[de facto standard|''de facto'' standards]] as well as formal standards.
Audio content encoded according usingin a particular audio coding format is normally usedencapsulated insidewithin a [[container format (digital)|container format]]. As such, the user normally doesn't have a raw [[Advanced Audio Coding|AAC]] file, but instead has a .m4a [[audio file format|audio file]], which is a [[MPEG-4 Part 14]] container containing AAC-encoded audio. The container also contains metadata such as title and other tags, and perhaps an index for fast seeking.<ref>http://superuser.com/questions/357686/where-is-synchronization-information-stored-in-container-formats</ref> A notable exception is [[MP3]] files, which are raw audio coding without a container format. De facto standards for adding metadata tagtags such as title and artist to MP3s, such as [[ID3]], are [[Hack_(computer_science)#In_computer_science|hack]]s which work by prepending the tags to the MP3, and then relying on the MP3 player to recognize the chunk as malformed audio coding and therefore skip it. In video files with audio, the encoded audio content is bundled with video (in a [[video coding format]]) inside a [[multimedia container format]].
An audio coding format does not dictate all [[algorithm]]s used by a [[codec]] implementing the format. An important part of how lossy audio compression works is by removing data in ways humans can't hear, according to a [[psychoacoustic model]]; the implementer of an encoder havehas some freedom of choice in which data to remove (according to their psycoaccusticpsychoacoustic model).
==Lossless, lossy, and uncompressed audio coding formats==
