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AU (.au)

Registered MIME type: audio/basic
AU audio format.
Used for digital audio in computer and telecommunication systems and on the web.
Supports a variety of audio codecs, including lossless uncompressed PCM, -law, a-law, and ADPCM voice compression.
Sometimes referred to as -law format or Unix Audio Format.
The -law algorithm is a standard method for compressing the dynamic range of a signal.
AU is an acronym derived from Audio.
Binary file format.
Supports various sampling frequencies and an arbitrary number of channels.
Identical to the SND format.
Developed by Sun Microsystems in 1992.
  • Import and Export support all audio codecs commonly used in the AU format.
  • Import imports an AU file, returning a sound object.
  • Export exports a sound object to an AU file encoded using 8-bit pulse code modulation.
  • Export["file.au", expr] creates an AU file from the sound object expr.
  • Import imports the specified element from an AU file.
  • Import imports multiple elements.
  • The import format can be specified with Import["file", "AU"] or Import.
  • Export creates an AU file by treating expr as specifying element elem.
  • Export treats each as specifying the corresponding .
  • Export exports expr with the specified option elements taken to have the specified values.
  • Export uses rules to specify the elements to be exported.
  • See the reference pages for full general information on Import and Export.
"Elements"list of elements and options available in this file
"Rules"full list of rules for each element and option
"Options"list of rules for options, properties and settings
  • Data representation elements:
"Data"raw audio samples, given as a list of lists of real numbers, each sublist representing an individual audio channel
"SampledSoundList"AU file given as SampledSoundList
"Sound"Sound object that plays as the sound
  • Multiple channels are represented as an array of audio samples.
"SampleRate"number of amplitude samples per second and channel
  • General option:
SampleRateAutomaticnumber of audio samples per second for each channel
  • Detailed properties and settings:
"AudioChannels"Automaticthe number of audio channels in the file
"AudioEncoding""Integer8"how samples are encoded
  • If the sample rate is not specified when exporting to AU, the highest sample rate occurring in the exported sound is used, and all sounds are resampled as necessary.
  • If the number of channels is unspecified, the highest number of simultaneous channels is taken, and silence is inserted if necessary.
  • If is set to a value n which is less than the number of channels to be exported, only the first n channels are exported.
  • The AU format supports PCM (pulse code modulation) and ADPCM (adaptive differential pulse code modulation) codecs, and various other audio encoding algorithms.
  • can be set to any of the following codecs:
"Integer8"8-bit PCM
"Integer16"16-bit PCM
"Integer24"24-bit PCM
"Integer32"32-bit PCM
"Real32"32-bit IEEE floating point
"Real64"64-bit IEEE floating point
"aLaw"a-Law 4-bit PCM (ITU-T G.711)
"uLaw"-Law 4-bit PCM (ITU-T G.711)
"G721-32"32 kbps ADPCM (ITU G.721)
"G723-24"G.723 encoding at 24 kbps
"G723-40"G.723 encoding at 40 kbps
  • Not all codecs support arbitrary sample rates and channel specifications.
Use Play to create a short sound sample, and export it to AU:
Use Play to create a short sound sample, and export it to AU:
In[1]:=
Click for copyable input
Out[1]=
In[2]:=
Click for copyable input
Out[2]=