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# frameLength

The current number of valid sample frames in the buffer.

```
var frameLength: AVAudioFrameCount { get set }
```

## Discussion

By default, the `frameLength` property doesn’t have a useful value upon creation, so you must set this property before using the buffer. The length must be less than or equal to the [`frameCapacity`](/documentation/AVFAudio/AVAudioPCMBuffer/frameCapacity) of the buffer. For deinterleaved formats, [`frameCapacity`](/documentation/AVFAudio/AVAudioPCMBuffer/frameCapacity) refers to the size of one channel’s worth of audio samples.

You may modify the length of the buffer as part of an operation that modifies its contents. Modifying `frameLength` updates the `mDataByteSize` field in each of the underlying <doc://com.apple.documentation/documentation/CoreAudioTypes/AudioBufferList> structure’s `AudioBuffer` properties correspondingly, and vice versa.

## See Also

[`frameCapacity`](/documentation/AVFAudio/AVAudioPCMBuffer/frameCapacity)

The buffer’s capacity, in audio sample frames.


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