The MPEG-4 Structured Audio Book

Authors : John Lazzaro and John Wawrzynek, Computer Science Division, University of California, Berkeley
Publication Date : 1999
Free License : GNU Free Documentation License

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Book Excerpts:

MPEG-4 Structured Audio (MP4-SA) is an ISO/IEC standard (edited by Eric Scheirer) that specifies sound not as audio data, but as a computer program that generates audio when run.

One implication of this design is that encoding content in MP4-SA is a creative act, not an automatic one. Or more specifically, two creative acts:

- Sound modeling. In MP4-SA, sound happens because a program written in the SAOL (pronounced "sail") computer language outputs audio samples. The algorithms coded in SAOL may model how musical instruments (like a piano or the human voice) create sound, or may process sounds (tasks like adding reverberation or mixing instrument sounds together).

- Sound sequencing. Performance is sound moving in time: notes play in sequence to make a melody, faders sweep across a mixing console to blend a performance, etc. In MP4-SA, the score language SASL (pronounced "sassil"), the MIDI standard, and the SAOL language itself are all available to support sound sequencing.

The goal of this book is to show how to use SAOL, SASL, and the other MP4-SA tools to create these two types of content. This book assumes some familiarity with computer programming and algorithms, audio signal processing, and music and sound.

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