SDIF: Sound Description Interchange Format

Effective musical application of the many sound analysis/synthesis tools now available has been hampered by the absence of a common representation for analyzed data. Although standard file formats abound for time-domain audio samples, each institution has its own file formats for other kinds of sound descriptions.

Sound descriptions supported by SDIF include

Features of SDIF

SDIF Data Format in a Nutshell

SDIF is optimized both for streaming and for archiving. The SDIF format is a sequence of time-tagged frames (IFF chunks), appearing in chronological order, with multiple kinds of frames allowed in a single file or stream. Thus, a single SDIF file might contain STFT results, a pitch estimate envelope, and sinusoidal tracks from the same original sound. A library of standard frame types defines formats for storing the common sound representations listed above.

Frames consist of some number of 2D matrices of floating point numbers, with each column corresponding to a parameter like frequency or amplitude and each row representing an object like a filter, sinusoid, or noise band.

A few optional chunk types can appear at the beginning of an SDIF file or stream, e.g., file creation info and one-time global information needed to configure synthesis software to interpret the chunk data.


This effort was suggested by Xavier Rodet of IRCAM. Discussions with scholars and vendors at the 1995 ICMC confirmed the need for this standard in the academic and commercial communities . Adrian Freed coined the name and invited ICMC delegates to participate in the development work. Discussions over the months led to new requirements for the standard particularly in the area of internet applications. Also, although originally conceived of as a portable (and not necessarily efficient) interchange format, CNMAT has decided to use it as the primary working format for its sound analysis and synthesis tools. This has resulted in a standard grounded in real needs and field tested.

CNMAT and IRCAM are nearing consensus on the final details of the format, and expect to publish a specification in the next few months. Already there is a library for reading and writing SDIF, and a growing set of tools for manipulating SDIF files.

We encourage feedback from all interested uses of SDIF.

Future Work

After we standardize the SDIF formats for sound representations now in common practice, we expect to experiment with the following topics and eventually add them to the standard:

WWW Site

The SDIF web site is