MPEG-4 Structured Audio
Encyclopedia
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.
It allows the transmission of synthetic music and sound effects at very low bit rate
s (from 0.01 to 10 kbps), 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:
MPEG-4 Structured Audio was cited by CNN as one of the top-25 innovations to arise at the Media Laboratory.
MPEG-4 Part 3
MPEG-4 Part 3 or MPEG-4 Audio is the third part of the ISO/IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods...
(ISO/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
14496-3:1999) in 1999.
It allows the transmission of synthetic music and sound effects at very low bit rate
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
s (from 0.01 to 10 kbps), and the description of parametric sound post-production
Post-production
Post-production is part of filmmaking and the video production process. It occurs in the making of motion pictures, television programs, radio programs, advertising, audio recordings, photography, and digital art...
for mixing multiple streams and adding effects
Sound effect
For the album by The Jam, see Sound Affects.Sound effects or audio effects are artificially created or enhanced sounds, or sound processes used to emphasize artistic or other content of films, television shows, live performance, animation, video games, music, or other media...
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 LanguageStructured Audio Orchestra LanguageStructured Audio Orchestra Language is an imperative, MUSIC-N programming language designed for describing virtual instruments, processing digital audio, and applying sound effects...
(SAOL), an audio programming languageProgramming languageA programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
. SAOL is historically related to CsoundCsoundCsound is a computer programming language for dealing with sound, also known as a sound compiler or an audio programming language, or more precisely, a C-based audio DSL. It is called Csound because it is written in C, as opposed to some of its predecessors...
and other so-called Music-NMUSIC-NMUSIC-N refers to a family of computer music programs and programming languages descended from or influenced by MUSIC, a program written by Max Mathews in 1957 at Bell Labs. MUSIC was the first computer program for generating digital audio waveforms through direct synthesis...
languages. It was created by an MIT Media LabMIT Media LabThe MIT Media Lab is a laboratory of MIT School of Architecture and Planning. Devoted to research projects at the convergence of design, multimedia and technology, the Media Lab has been widely popularized since the 1990s by business and technology publications such as Wired and Red Herring for a...
grad student named Eric Scheirer while he was studying under Barry VercoeBarry VercoeBarry Vercoe is a New Zealand-born computer scientist and composer. He completed his undergraduate degree in New Zealand in Music and Mathematics and went on to complete a Ph.D. at the University of Michigan, USA, in Music Composition. In 1968, Vercoe's research in Digital Audio Processing paved...
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 synthesisWavetable synthesisWavetable synthesis is used in certain digital music synthesizers to implement a restricted form of real-time additive synthesis. The technique was first developed by Wolfgang Palm of PPG in the late 1970s and published in 1979, and has since been used as the primary synthesis method in...
- 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.
External links
- MPEG-4 Structured Audio Developer Tools
- [ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg4/documents/w2203/w2203sa.pdf MPEG-4 Part 3 Subpart 5: Structured Audio, Final Committee Draft, N2203SA, 1998]
- The MPEG-4 Structured Audio standard - Eric D. Scheirer, MIT Media Laboratory
- Official MPEG web site