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Re: kAudioUnitProperty_Latency property changes and Logic
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Re: kAudioUnitProperty_Latency property changes and Logic

  • Subject: Re: kAudioUnitProperty_Latency property changes and Logic
  • From: Paul Davis <email@hidden>
  • Date: Tue, 31 May 2016 17:14:22 -0400
I can answer on behalf of Ardour and Mixbus.

We don't pay attention to Property_Latency because we are not willing to deal with the plugin invoking such a change at arbitary times. We check latency at times when we are willing to deal with having changed, and ignore "asynchronous" changes caused at other times. In our case, we specifically check at transport stop (not transport start, since we don't wish to emulate the "slow-start" behaviour of other well-known DAWs, at least historically).

So, you can send your notifications, but in our case, we aren't interested. We'll pick up your provided value when we are.


On Tue, May 31, 2016 at 4:56 PM, Howard Moon <email@hidden> wrote:
Our software allows users to change the latency associated with the Audio Unit plug-in, but it seems that Logic is ignoring this change. I have looked all over, and found others reporting this problem a few years ago, but I don’t see a resolution anywhere. Here is the code we’re using:

AudioUnitEvent auEvent;
auEvent.mArgument.mProperty.mAudioUnit = GetComponentInstance ();
auEvent.mArgument.mProperty.mPropertyID = kAudioUnitProperty_Latency;
auEvent.mArgument.mProperty.mScope = kAudioUnitScope_Global;
auEvent.mArgument.mProperty.mElement = 0;
auEvent.mEventType = kAudioUnitEvent_PropertyChange;
AUEventListenerNotify (paramListenerRef, NULL, &auEvent);

I did find one thread that said they got it working, but it didn’t elaborate as to exactly *how* they accomplished it other than a very general statement:

Finally found it. So, you need to manage list of property listeners, and whenever this happens ask all property listeners. Ugly, but I spent some time looking into the horrible CoreAudio SDK and that's how they do it...


I’m just not sure exactly how that would be accomplished.

Does anyone know how to get this to work in Logic (and any other hosts that seem to ignore the AUEventListenerNotify() call above)? Got a code snippet?

Thanks,
-Howard



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