Inside Macintosh: Sound

Sound Files

This section describes in detail the structure of AIFF and AIFF-C files. Both of these types of sound files are collections of chunks that define characteristics of the sampled sound or other relevant data about the sound.

Most applications only need to read AIFF and AIFF-C files or to record sampled-sound data directly to them. You can both play and record AIFF and AIFF-C files without knowing the details of the AIFF and AIFF-C file formats, as explained in the chapter "Introduction to Sound on the Macintosh" in this book. Thus, the information in this section is for advanced programmers only.

Currently, the AIFF and AIFF-C specifications include the following chunk types.

Chunk type	Description
Form Chunk	Contains information about the format of an AIFF or AIFF-C file and contains all the other chunks of such a file.
Format Version Chunk	Contains an indication of the version of the AIFF-C specification according to which this file is structured (AIFF-C only).
Common Chunk	Contains information about the sampled sound such as the sampling rate and sample size.
Sound Data Chunk	Contains the sample frames that comprise the sampled sound.
Marker Chunk	Contains markers that point to positions in the sound data .
Comments Chunk	Contains comments about markers in the file .
Sound Accelerator Chunk	Contains information intended to allow applications to accelerate the decompression of compressed audio data .
Instrument Chunk	Defines basic parameters that an instrument (such as a sampling keyboard) can use to play back the sound data .
MIDI Data Chunk	Contains MIDI data.
Audio Recording Chunk	Contains information pertaining to audio recording devices.
Application Specific Chunk	Contains application-specific information.
Name Chunk	Contains the name of the sampled sound.
Author Chunk	Contains one or more names of the authors (or creators) of the sampled sound.
Copyright Chunk	Contains a copyright notice for the sampled sound.
Annotation Chunk	Contains a comment.

The following sections document the four principal kinds of chunks that can occur in AIFF and AIFF-C files.

Sound Files

Chunk Organization and Data Types

The Form Chunk

The Format Version Chunk

The Common Chunk

The Sound Data Chunk

Format of Entire Sound Files