# Multichannel AU plugins

**URL:** <https://forum.juce.com/t/multichannel-au-plugins/8836>\
**Category:** Audio Plugins\
**Created:** [June 14, 2012, 5:31pm UTC](https://forum.juce.com/t/multichannel-au-plugins/8836 "2012-06-14T17:31:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![rc-odl](https://avatars.discourse-cdn.com/v4/letter/r/43a26b/32.png) [@rc-odl](https://forum.juce.com/u/rc-odl)\
**Post date:** [June 14, 2012, 5:31pm UTC](https://forum.juce.com/t/multichannel-au-plugins/8836/1 "2012-06-14T17:31:16Z")

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Hi Jules,

Further to this thread from 2008 [http://www.rawmaterialsoftware.com/viewtopic.php?f=8&t=3421](http://www.rawmaterialsoftware.com/viewtopic.php?f=8&t=3421) it seems that Juce plugins which don’t support a 2-in/2-out channel config still fail AU Validation with error kAudioUnitErr\_FormatNotSupported (-10868). What’s worse is that Reaper refuses point blank to use one of the supported configs.

Can I suggest that something like the following is added at the end of the JuceAU constructor?

[code] CreateElements();  
CAStreamBasicDescription streamDescription;  
streamDescription.mSampleRate = GetSampleRate();

```
    streamDescription.SetCanonical(channelConfigs[0][0], false);
    Inputs.GetIOElement(0)->SetStreamFormat(streamDescription);
    
    streamDescription.SetCanonical(channelConfigs[0][1], false);
    Outputs.GetIOElement(0)->SetStreamFormat(streamDescription);[/code]

```

This was sufficient for my needs, but you’ll probably want to add a special case for #ifdef JucePlugin\_IsSynth and maybe default to {2,2} if it’s available instead of the first one on the list.

Rupert

Reference: [http://www.soundsorange.net/resources/developing-audio-units-for-mac-osx/multi-channel-aus/](http://www.soundsorange.net/resources/developing-audio-units-for-mac-osx/multi-channel-aus/)

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**Author:** ![jules](https://avatars.discourse-cdn.com/v4/letter/j/41988e/32.png) [@jules](https://forum.juce.com/u/jules)\
**Post date:** [June 15, 2012, 8:17am UTC](https://forum.juce.com/t/multichannel-au-plugins/8836/2 "2012-06-15T08:17:11Z")

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Thanks!

I’ve added some code along these lines now… I’d appreciate any feedback from people as to whether it helps/works!