Editing Audio file format (section)

==Format types==

It is important to distinguish between the [[audio coding format]], the [[Container format (digital)|container]] containing the [[Raw audio format|raw audio data]], and an [[audio codec]]. A codec performs the encoding and decoding of the raw audio data while this encoded data is (usually) stored in a container file. Although most audio file formats support only one type of audio coding data (created with an [[audio codec|audio coder]]), a multimedia container format (as [[Matroska]] or [[Audio Video Interleave|AVI]]) may support multiple types of audio and video data.

There are three major groups of audio file formats:

* Uncompressed audio formats, such as [[WAV]], [[Audio Interchange File Format|AIFF]], [[Au file format|AU]] or [[raw audio format|raw]] header-less [[PCM]]; Note wav can alternatively use compression.
* Formats with [[lossless compression]], such as [[FLAC]], [[Monkey's Audio]] ([[filename extension]] <code>.ape</code>), [[WavPack]] ([[filename extension]] <code>.wv</code>), TTA, [[ATRAC]] Advanced Lossless, [[Apple Lossless|ALAC]], [[MPEG-4 SLS]], [[MPEG-4 ALS]], [[MPEG-4 DST]], [[Windows Media Audio#Windows Media Audio Lossless|Windows Media Audio Lossless (WMA Lossless)]], and [[Shorten (file format)|Shorten]] (SHN).
* Formats with [[lossy compression]], such as [[Opus (audio format)|Opus]], [[MP3]], [[Vorbis]], [[Musepack]], [[Advanced Audio Coding|AAC]], [[ATRAC]] and [[Windows Media Audio#WIndows Media Audio Lossy|Windows Media Audio Lossy (WMA lossy)]].

===Uncompressed audio format===
{{See also|Raw audio format | Uncompressed video}}
One major uncompressed audio format, [[LPCM]], is the same variety of PCM as used in [[Compact Disc Digital Audio]] and is the format most commonly accepted by low level audio [[API]]s and [[D/A converter]] hardware. Although LPCM can be stored on a computer as a [[raw audio format]], it is usually stored in a <code>.wav</code> file on [[Windows]] or in a <code>.aiff</code> file on [[macOS]]. The [[Audio Interchange File Format]] (AIFF) format is based on the [[Interchange File Format]] (IFF), and the WAV format is based on the similar [[Resource Interchange File Format]] (RIFF). WAV and AIFF are designed to store a wide variety of audio formats, lossless and lossy; they just add a small, [[metadata]]-containing header before the audio data to declare the format of the audio data, such as LPCM with a particular [[sampling (signal processing)|sample rate]], [[audio bit depth|bit depth]], [[endianness]] and number of [[audio channel|channels]]. Since WAV and AIFF are widely supported and can store LPCM, they are suitable file formats for storing and archiving an original recording.

[[Broadcast Wave Format|BWF]] (Broadcast Wave Format) is a standard audio format created by the [[European Broadcasting Union]] as a successor to WAV. Among other enhancements, BWF allows more robust [[metadata]] to be stored in the file. See ''[[Broadcast Wave Format|European Broadcasting Union: Specification of the Broadcast Wave Format]]'' (EBU Technical document 3285, July 1997). This is the primary recording format used in many professional audio workstations in the television and film industry. BWF files include a standardized [[timestamp]] reference which allows for easy synchronization with a separate picture element. Stand-alone, file based, multi-track recorders from AETA,<ref>{{Cite web|url=http://www.aeta-audio.com/ |title=AETA AUDIO SYSTEMS: home |date=2016-01-29 |url-status=dead |archive-url=https://web.archive.org/web/20160129100145/http://www.aeta-audio.com/ |archive-date=January 29, 2016 }}</ref> Sound Devices,<ref>{{cite web|url=http://www.sounddevices.com/|title=Sound Devices - Home|website=www.sounddevices.com}}</ref> Zaxcom,<ref>{{cite web|url=https://zaxcom.com/|title=Zaxcom|website=zaxcom.com}}</ref> HHB Communications Ltd,<ref>{{cite web|url=https://www.hhb.co.uk/|title=- HHB|website=www.hhb.co.uk}}</ref> [[Fostex]], Nagra, Aaton,<ref>{{Cite web|url=http://aaton.com|title=Aaton Digital|website=aaton.com}}</ref> and [[TASCAM]] all use BWF as their preferred format.

===Lossless compressed audio format===
A lossless compressed audio format stores data in less space without losing any information. The original, uncompressed data can be recreated from the compressed version.

Uncompressed audio formats encode both sound and silence with the same number of bits per unit of time. Encoding an uncompressed minute of absolute silence produces a file of the same size as encoding an uncompressed minute of music. In a lossless compressed format, however, the music would occupy a smaller file than an uncompressed format and the silence would take up [[Silence compression|almost no space]] at all.

Lossless compression formats include [[FLAC]], [[WavPack]], [[Monkey's Audio]], [[Apple Lossless Audio Codec|ALAC]] (Apple Lossless). They provide a compression ratio of about 2:1 (i.e. their files take up half the space of PCM). Development in lossless compression formats aims to reduce processing time while maintaining a good compression ratio.

===Lossy compressed audio format===
Lossy audio format enables even greater reductions in file size by removing some of the audio information and simplifying the data. This, of course, results in a reduction in audio quality, but a variety of techniques are used, mainly by exploiting [[psychoacoustics]], to remove the parts of the sound that have the least effect on perceived quality, and to minimize the amount of audible noise added during the process. The popular [[MP3|MP3 format]] is probably the best-known example, but the [[AAC format]] found on the iTunes Music Store is also common. Most formats offer a range of degrees of compression, generally measured in [[bit rate]]. The lower the rate, the smaller the file and the more significant the quality loss.