 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (January 2013) |
| Filename extension |
.au .snd |
|---|---|
| Internet media type | audio/basic (headerless format)[1] |
| Type code | |
| Magic number | .snd (newer versions) |
| Developed by | Sun Microsystems |
| Type of format | audio file format, container format |
| Container for | Audio, most often μ-law |
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-encoded data at an 8000 Hz sample rate.[1] Hardware from other vendors often used sample rates as high as 8192 Hz, often integer multiples of video clock signal frequencies. Newer files have a header that consists of six unsigned 32-bit words, an optional information chunk which is always of non-zero size, and then the data (in big-endian format).
Although the format now supports many 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.
- ^ a b "audio/basic". IANA.org. Retrieved 23 February 2023.
- ^ "AVFileTypeSunAU". Apple Developer Documentation. Apple Inc.
- ^ "System-Declared Uniform Type Identifiers". Uniform Type Identifiers Reference. Apple Inc.