Machine Tongues XVIII: A Child’s Garden of Sound File Formats

Practitioners of computer music often need to store sound as sampled digital data on their computer's hard disks, digital audio tapes (DATs), or compact disks (CDs). The data formats used to represent digitally sampled sound determine the audio quality of the sound capture, the amount of disk or tape needed to store the data, and the ease with which application programs can be developed to manipulate sound data. Sound file systems are software packages that provide standardized data structures for sampled sounds in order to enable real-time recording and playback, to ease the development of sound-processing software tools, and to increase the interoperability of related utility programs. Sound file systems differ in what kind of support they offer for compact and efficient sample storage on disk, real-time sound I/O, data interchange between programs, and sound manipulation and annotation. The components of such a system include the disk-based storage format, in-memory data structures, function libraries for processing sound data (the application programming interface or API), and some collection of end-user utility programs, for example to play and record sounds. This article introduces a few of the many ways that sound data can be stored in computer files, and describes several of the file formats that are in common use for this purpose. This text is an expanded and edited version of a " frequently asked questions " (FAQ) document that is updated regularly by one of the authors (van Rossum). Extensive references are given here to printed and network-accessible machine-readable documentation and source code resources. The FAQ document is regularly posted to the USENET electronic news groups alt.binaries.sounds and comp.dsp for maximal coverage of people interested in digital audio, and to comp.answers, for easy reference. It is available by anonymous Internet file transfer