A brief Intro to Structured Audio
by John Lazzaro.

Structured Audio (SA) is a new file format, that's part of the upcoming MPEG 4 Audio standard. MP4-SA is different from other audio file formats, like MP3 and RA and WAV, in a fundamental way: Instead of describing the audio data on the master tape, it describes the music-making process -- the instruments and effects and mixing console that were used, the notes played, and the slider and knob movements. It describes these things in such a precise way, that its possible to perfectly recreate the audio by following the description. What's the advantage to taking this approach? Consider these scenarios: [1] Musicians can collaborate on a performance by passing around an MP4-SA file of the work in progress. Different sequencer and soft-synth programs will all be able to read these MP4-SA files, and convert them into audio that sounds identical to all the collaborators (the power of an open ISO standard, as compared to a closed format controlled by a single company). A new part gets added to the performance by adding to the MP4-SA file -- adding new performance data as well as new computer models of instruments and effects. [2] You want to create a musical performance as part of a video game, where the moods of the characters modulate the music. Or you want to create a stand-alone musical performance, that downloads the current weather from the web for the listeners location, and modulates the music off this data. Since the MP4-SA file describes the music-making process, not the audio data, these sorts of interactive performances are possible. So are, incidently, non-musical audio applications like audiology tests over the Internet. [3] You want to create a 1-minute performance of interesting music with complex timbres, that fits in a 3Kbyte file -- that's smaller than the size of the M-station JPEG at the top of this page! This is possible with MP4-SA, if you make the right choices for instruments and effects models, and if you use algorithmic composition techniques. Sound interesting? To be fair, MP4-SA is really technology in progress -- its been recently standardized by MPEG, under the leadership of the MIT Media Lab's Eric Scheirer. But there is free software available now to experiment with MP4-SA, and musicians who feel comfortable with simple computer programming can make interesting music -- see what these musicians have done with the tools, for example: studio147.nl.eu.org/saol To learn more about MP4-SA, and to download software that runs under Linux (and to a lesser extent, under Windows) to experiment yourself, go here: www.cs.berkeley.edu/~lazzaro/sa

 home  music  news  opinion  software  tips  email