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# kAudioUnitProperty_SupportedNumChannels

A read-only array of channel information structures valid on the audio unit global scope.

```
var kAudioUnitProperty_SupportedNumChannels: AudioUnitPropertyID { get }
```

## Discussion

The size of the array indicates the number of [`AUChannelInfo`](/documentation/AudioToolbox/AUChannelInfo) structures for an audio unit. Each structure describes the channel configuration for an audio input/output bus. For example, the values (2, 2) indicates a channel configuration of two input channels paired to two output channels on a bus.

A negative value for a field in an [`AUChannelInfo`](/documentation/AudioToolbox/AUChannelInfo) structure indicates that an input/output bus supports a variable number of channels, as follows:

- {–1, –1} indicates that a bus supports any number of input or output channels provided that the input and output channel counts match each other. This is the default configuration for effect units.
- {–1, –2} or {–2, –1} indicates that a bus supports any number of input and output channels; the channel counts on input and output can differ from each other.
- {–1, –3} indicates that a bus supports any number of input channels and up to three output channels.

A value of 0 for the `inChannels` field means that an audio unit does not have any audio input buses.

---

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