---
title: kAudioUnitProperty_SupportedNumChannels
framework: audiotoolbox
role: symbol
role_heading: Global Variable
path: audiotoolbox/kaudiounitproperty_supportednumchannels
---

# kAudioUnitProperty_SupportedNumChannels

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

## Declaration

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

## Discussion

Discussion The size of the array indicates the number of 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 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.

## See Also

### Properties

- [kAudioUnitProperty_ElementCount](audiotoolbox/kaudiounitproperty_elementcount.md)
- [kAudioUnitProperty_AudioChannelLayout](audiotoolbox/kaudiounitproperty_audiochannellayout.md)
- [kAudioUnitProperty_AudioUnitMIDIProtocol](audiotoolbox/kaudiounitproperty_audiounitmidiprotocol.md)
- [kAudioUnitProperty_AUHostIdentifier](audiotoolbox/kaudiounitproperty_auhostidentifier.md)
- [kAudioUnitProperty_BypassEffect](audiotoolbox/kaudiounitproperty_bypasseffect.md)
- [kAudioUnitProperty_ClassInfo](audiotoolbox/kaudiounitproperty_classinfo.md)
- [kAudioUnitProperty_ClassInfoFromDocument](audiotoolbox/kaudiounitproperty_classinfofromdocument.md)
- [kAudioUnitProperty_CocoaUI](audiotoolbox/kaudiounitproperty_cocoaui.md)
- [kAudioUnitProperty_ContextName](audiotoolbox/kaudiounitproperty_contextname.md)
- [kAudioUnitProperty_CPULoad](audiotoolbox/kaudiounitproperty_cpuload.md)
- [kAudioUnitProperty_DependentParameters](audiotoolbox/kaudiounitproperty_dependentparameters.md)
- [kAudioUnitProperty_ElementName](audiotoolbox/kaudiounitproperty_elementname.md)
- [kAudioUnitProperty_FactoryPresets](audiotoolbox/kaudiounitproperty_factorypresets.md)
- [kAudioUnitProperty_FastDispatch](audiotoolbox/kaudiounitproperty_fastdispatch.md)
- [kAudioUnitProperty_FrequencyResponse](audiotoolbox/kaudiounitproperty_frequencyresponse.md)