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# AVAudioSession.IOType.notSpecified

The default audio session I/O type.

```
case notSpecified
```

## Discussion

Use this I/O type if your app doesn’t use <doc://com.apple.documentation/documentation/AVFoundation/AVCaptureSession>, or doesn’t have any specific requirements for aggregating input and output audio in the same realtime I/O callback. If your app doesn’t use a capture session, it gets aggregated I/O when using the [`playAndRecord`](/documentation/AVFAudio/AVAudioSession/Category-swift.struct/playAndRecord) category.

If your app uses a capture session, specifying this value allows the session to start recording without causing glitches in the already running output audio. It also allows the system to use power-saving optimizations.

---

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