Editing Au file format (section)

{{Short description|Simple audio file format}}
{{Infobox file format
| name = Au
| icon =
| logo =
| screenshot =
| caption =
| extension = .au<br />.snd
| _nomimecode = yes
| mime = {{code|audio/basic}} (headerless format)<ref name=IANA>{{cite web |title=audio/basic |url=https://www.iana.org/assignments/media-types/audio/basic |website=IANA.org |access-date=23 February 2023}}</ref>
| type code = {{plainlist|
* public.au-audio<ref>{{cite web |url=https://developer.apple.com/documentation/avfoundation/avfiletypesunau |title=AVFileTypeSunAU |work=Apple Developer Documentation |publisher=[[Apple Inc.]]}}</ref>
* public.ulaw-audio<ref>{{cite web |url=https://developer.apple.com/library/archive/documentation/Miscellaneous/Reference/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html |title=System-Declared Uniform Type Identifiers |work=Uniform Type Identifiers Reference |publisher=[[Apple Inc.]]}}</ref> (headerless variant)
}}
| uniform type =
| magic = {{code|.snd}} (newer versions)
| owner = [[Sun Microsystems]]
| genre = [[audio file format]], [[container format]]
| container for = [[Audio frequency|Audio]], most often [[μ-law algorithm|μ-law]]
| contained by =
| extended from =
| extended to =
| standard =
}}
The '''Au file format''' is a simple [[audio file format]] introduced by [[Sun Microsystems]]. The format was common on [[NeXT]] systems and on early Web pages. Originally it was headerless, being 8-bit [[μ-law algorithm|μ-law]]-encoded data at an 8000 Hz sample rate.<ref name=IANA/> Hardware from other vendors often used sample rates as high as 8192&nbsp;Hz, often integer multiples of video clock signal frequencies. Newer files have a header that consists of six [[Signedness|unsigned]] [[32-bit computing|32-bit]] words, an optional information chunk which is always of non-zero size, and then the data (in [[Endianness|big-endian]] format).

Although the format now supports many [[digital audio|audio encoding]] formats, it remains associated with the μ-law logarithmic encoding. This encoding was native to the [[SPARCstation 1]] hardware, where [[SunOS]] exposed the encoding to application programs through the '''/dev/audio''' [[device file]] interface. This encoding and interface became a [[de facto]] standard for [[Unix]] sound.