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# Bit rate atom ('btrt')

An atom that signals the bit rate information of a stream.

## Overview

The optional bit rate atom may be present at the end of any timed metadata sample description to signal the bit rate information of a stream. The bit rate information can be used for buffer configuration.

The layout of a bit rate atom is as follows:

|Data field                                                                                 |Bytes|
|-------------------------------------------------------------------------------------------|-----|
|``doc://com.apple.qtff/documentation/quicktime-file-format/Bit_rate_atom/Size``            |4    |
|``doc://com.apple.qtff/documentation/quicktime-file-format/Bit_rate_atom/Type`` = `'btrt'` |4    |
|``doc://com.apple.qtff/documentation/quicktime-file-format/Bit_rate_atom/Buffer_size``     |4    |
|``doc://com.apple.qtff/documentation/quicktime-file-format/Bit_rate_atom/Max_bit_rate``    |4    |
|``doc://com.apple.qtff/documentation/quicktime-file-format/Bit_rate_atom/Average_bit_rate``|4    |

## Topics

### Data fields

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

A 32-bit unsigned integer that indicates the size in bytes of the atom structure.

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

A 32-bit unsigned integer value.

[`Buffer size`](/documentation/quicktime-file-format/Bit_rate_atom/Buffer_size)

A 32-bit unsigned integer that indicates the suggested size of the associated data buffer.

[`Max bit rate`](/documentation/quicktime-file-format/Bit_rate_atom/Max_bit_rate)

A 32-bit unsigned integer that indicates the maximum bit rate in bits/second of the associated media stream.

[`Average bit rate`](/documentation/quicktime-file-format/Bit_rate_atom/Average_bit_rate)

A 32-bit unsigned integer that indicates the average bit rate in bits/second of the associated media stream.


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