---
title: "siDecompressionParam atom ('wave')"
framework: quicktime-file-format
role: symbol
role_heading: Atom
path: quicktime-file-format/sidecompressionparam_atom
---

# siDecompressionParam atom ('wave')

An atom that stores data specific to a given audio decompressor.

## Mentioned in

Sound sample data

## Overview

Overview The siDecompressionParam atom provides the ability to store data specific to a given audio decompressor in the SoundDescription record. As example, some audio decompression algorithms, such as Microsoft’s ADPCM, require a set of out-of-band values to configure the decompressor. These are stored in an atom of this type. This atom contains other atoms with audio decompressor settings and is a required extension to the sound sample description for MPEG-4 audio. A 'wave' chunk for 'mp4a' typically contains (in order) at least a 'frma' atom, an 'mp4a' atom, an 'esds' atom, and a Terminator atom ('0x00000000'). The contents of other siDecompressionParam atoms are dependent on the audio decompressor.

## Topics

### Data fields

- [Size](quicktime-file-format/sidecompressionparam_atom/size.md)
- [Type](quicktime-file-format/sidecompressionparam_atom/type.md)
- [Extension atoms](quicktime-file-format/sidecompressionparam_atom/extension_atoms.md)

## See Also

### Extending sound sample descriptions

- [siSlopeAndIntercept atom](quicktime-file-format/sislopeandintercept_atom.md)
- [Format atom ('frma')](quicktime-file-format/format_atom.md)
- [Terminator atom ('0x00000000')](quicktime-file-format/terminator_atom.md)
- [MPEG-4 elementary stream descriptor atom  ('esds')](quicktime-file-format/mpeg-4_elementary_sound_stream_descriptor_atom.md)
- [Audio channel layout atom ('chan')](quicktime-file-format/audio_channel_layout_atom.md)
- [Subtitle follows track reference atom ('folw')](quicktime-file-format/subtitle_follows_track_reference_atom.md)