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# AVC decoder configuration atom ('avcC')

A required extension to the video sample description for H.264 video.

## Overview

This atom contains an MPEG-4 decoder configuration atom. This is a required extension to the video sample description for H.264 video. This extension appears in video sample descriptions only when the codec type is `‘avc1’`.

> Note: The decoder configuration record that this atom contains is defined in the MPEG-4 specification ISO/IEC FDIS 14496-15.

## Topics

### Data fields

[`Size`](/documentation/quicktime-file-format/AVC_decoder_configuration_atom/Size)

An unsigned 32-bit integer holding the size of the AVC decoder configuration atom.

[`Type`](/documentation/quicktime-file-format/AVC_decoder_configuration_atom/Type)

An unsigned 32-bit field.

[`AVC decoder configuration record`](/documentation/quicktime-file-format/AVC_decoder_configuration_atom/AVC_decoder_configuration_record)

A record that configures the AVC decoder.


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