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# QuickTime audio codec type

## Overview

- Containing profile atom: Track (sound), movie
- `part-ID`: `0x20202020` (universal feature)
- `feature-code`: `'afmt'`
- `feature-value`: Unsigned `int(32)` (a four-character-code) holding the QuickTime audio codec type copied from `SoundDescription` structure’s `dataFormat` field

## Feature Values

This is the four-character-code found in a sound sample description.

Examples: `'mp4a'`, `'twos'`.

## Writer Responsibilities

A writer of the QuickTime audio codec type feature should record the four-character-code corresponding to the QuickTime audio format type or types also recorded in the sound track’s sample descriptions.

> Note: A writer that records the QuickTime Audio Codec type for the `'mp4a'` codec is encouraged also to write the MPEG-4 Audio Codec feature.

## Feature Value Algorithm

The feature value is the audio codec type read from a `SoundDescription` structure’s `dataFormat` field. If there are multiple sample descriptions with different audio codec types, either all QuickTime Audio Codec Type features must be recorded in the profile atom or none must be recorded.

## Reader Responsibilities

A reader of this feature code should compare the recorded value by an equality comparison (using =) with the format codes supported by the reader.

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