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# init(streamDescription:)

Creates an audio format instance from a stream description.

```
init?(streamDescription asbd: UnsafePointer<AudioStreamBasicDescription>)
```

## Parameters

`asbd`

The audio stream description.

## Return Value

A new `AVAudioFormat` instance, or `nil` if the initialization fails.

## Discussion

If the <doc://com.apple.documentation/documentation/CoreAudioTypes/AudioStreamBasicDescription> specifies more than two channels, this method fails and returns `nil`. Instead, use the [`init(streamDescription:channelLayout:)`](/documentation/AVFAudio/AVAudioFormat/init(streamDescription:channelLayout:)) method.

---

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