MPEG-4 Structured Audio

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MPEG-4 Structured Audio is an ISO/IEC standard for describing sound. It was published as subpart 5 of MPEG-4 Part 3 (ISO/IEC 14496-3:1999) in 1999.[1][2][3][4]

It allows the transmission of synthetic music and sound effects at very low bit rates (from 0.01 to 10 kbit/s), and the description of parametric sound post-production for mixing multiple streams and adding effects to audio scenes. It does not standardize a particular set of synthesis methods, but a method for describing synthesis methods.

The sound descriptions generate audio when compiled (or interpreted) by a compliant decoder. MPEG-4 Structured Audio consists of the following major elements:

  • Structured Audio Orchestra Language (SAOL), an audio programming language. SAOL is historically related to Csound and other so-called Music-N languages. It was created by an MIT Media Lab grad student named Eric Scheirer while he was studying under Barry Vercoe during the 1990s.
  • Structured Audio Score Language (SASL) - is used to describe the manner in which algorithms described in SAOL are used to produce sound.
  • Structured Audio Sample Bank Format (SASBF) - allows for the transmission of banks of audio samples to be used in wavetable synthesis
  • A normative Structured Audio scheduler description - it is the supervisory run-time element of the Structured Audio decoding process.
  • MIDI support - provides important backward-compatibility with existing content and authoring tools.

MPEG-4 Structured Audio was cited by CNN as one of the top-25 innovations to arise at the Media Laboratory.[5]

See also[edit]


  1. ^ ISO (1999). "ISO/IEC 14496-3:1999 - Information technology -- Coding of audio-visual objects -- Part 3: Audio". ISO. Retrieved 2009-10-06. 
  2. ^ ISO/IEC JTC 1/SC 29/WG 11 (1998-05-15), ISO/IEC FCD 14496-3 Subpart 5 - Information Technology - Coding of Audiovisual Objects – Low Bitrate Coding of Multimedia Objects, Part 3: Audio, Subpart 5: Structured Audio, Final Committee Draft, N2203SA (PDF), retrieved 2009-10-10 
  3. ^ D. Thom, H. Purnhagen, and the MPEG Audio Subgroup (October 1998). "MPEG Audio FAQ Version 9 - MPEG-4". Retrieved 2009-10-06. 
  4. ^ Heiko Purnhagen (2001-06-01). "The MPEG-4 Audio Standard: Overview and Applications". Heiko Purnhagen. Retrieved 2009-10-07. [dead link]
  5. ^ "THE BIG I: MIT Media Lab Turns 25". CNN. 

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