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# AudioStreamPacketDescription

A value that describes a packet in a buffer of audio data.

```
struct AudioStreamPacketDescription
```

## Overview

For data formats where the packet size isn’t constant, such as variable bit rate data and data where the channels have unequal sizes, use this structure to supplement the information in the [`AudioStreamBasicDescription`](/documentation/CoreAudioTypes/AudioStreamBasicDescription) structure.

## Topics

### Inspecting an audio stream packet description

[`mDataByteSize`](/documentation/CoreAudioTypes/AudioStreamPacketDescription/mDataByteSize)

The number of bytes in the packet.

[`mStartOffset`](/documentation/CoreAudioTypes/AudioStreamPacketDescription/mStartOffset)

The number of bytes from the start of the buffer to the beginning of the packet.

[`mVariableFramesInPacket`](/documentation/CoreAudioTypes/AudioStreamPacketDescription/mVariableFramesInPacket)

The number of sample frames of data in the packet.

### Creating an audio stream packet descripiton

[`init()`](/documentation/CoreAudioTypes/AudioStreamPacketDescription/init())

Creates an audio stream basic description.

[`init(mStartOffset:mVariableFramesInPacket:mDataByteSize:)`](/documentation/CoreAudioTypes/AudioStreamPacketDescription/init(mStartOffset:mVariableFramesInPacket:mDataByteSize:))

Creates an audio stream basic description with the start offset, and the number of sample frames and bytes in the packet that you specify.


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