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Re: simultaneous parameter changes
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Re: simultaneous parameter changes


  • Subject: Re: simultaneous parameter changes
  • From: Chad Wagner <email@hidden>
  • Date: Tue, 20 Mar 2007 22:42:20 -0400

yup, that does help, thanks for the info. not only does it help me understand how the host is interacting with my plugin (in case Ableton ever gets back to me [not holding my breath] I can clearly explain it to them), but also the correct way to set parameters from my own GUI -- I was using AUParameterSet but I did not know what it really did.

is there somewhere that stuff like that is documented so I can read up on it?

thanks!


On Mar 20, 2007, at 3:59 PM, William Stewart wrote:

Its a two step process:
(1) set the parameter on the audio unit
(2) notify any listeners that the parameter value has changed
	- listeners can have different granularities for notifications, etc.

So, for a host app to correct set parameters, it can either do:
(1) call AudioUnitSetParameter (declared in AudioUnit/ AUComponent.h) with the new parameter value
(2) call AUEventListenerNotify ( declared in AudioToolbox/ AudioUnitUtilities.h) with the information that it just changed the value of the specified parameter


or
(1) call AUParameterSet ( declared in AudioToolbox/ AudioUnitUtilities.h) which does (1) and (2) above for you


HTH

Bill

On 19/03/2007, at 11:07 AM, Chad Wagner wrote:

I did some more tests in Live with other plugins, and in other apps with my plugin, and I'm convinced that you are right (even though I still don't fully understand the role of the host). I sent a report to Ableton, we'll see if they do anything with it...
As long as it's not my plugin that's at fault I'm okay with it ;-p


Thanks again for the help.


On Mar 17, 2007, at 8:34 PM, Chad Wagner wrote:

Hi Bill, thanks for the response.

I guess I don't understand enough of how an AU host is supposed to work. So even though AudioUnitBaseSetParameter gets called twice (once for each parameter), there's another step that's missing? There's an opaque step in there so I can't figure out exactly what's supposed to happen or where it is falling short...

If I break in AudioUnitBaseSetParameter so that the two "simultaneous" calls actually get some space between them, then the listener proc is called twice as expected, which is why I suspected my notification interval was the problem. If this really is a bug in Live, I'd like to understand the issue a little better before pursuing it with them, and also be sure it's not just something I'm doing wrong (which was my first assumption)



On Mar 16, 2007, at 9:50 PM, William Stewart wrote:

AUEventListener doesn't make decisions about parameters being changed or not - if the caller is telling us that both X and Y parameter is being changed, you should be receiving notifications for both - this sounds like a bug in Live - they aren't calling the event listener, just calling AudioUnitSetParameter - you should contact them

Bill

On 15/03/2007, at 8:04 AM, Chad Wagner wrote:

Hopefully this is an easy question, but it's been giving me some problems, so any help would be appreciated.

In my AU's carbon view, I set up an event listener with AUEventListenerCreate, using a notification interval and granularity of 0.1 sec. I'm testing it in Ableton Live, which has a generic 2D control that can be mapped to any 2 parameters of the AU. When using this, both parameter changes are received correctly by the AU, but my AUEventListenerProc in the GUI is only called once for one of the parameters, i.e. if both X and Y values change, I am only notified of X. (I am notified of Y only if there was no change in X.) I assume this has to do with the granularity setting, so I tried reducing that (which isn't really what I want) and also tried creating a different listener for each parameter (though still using the same callback proc), but still with the same results.

I'd like the notification interval and granularity to stay at 0.1 sec, since I really don't care about changes that come faster than that, but I do need to track each parameter independently and be notified of the current values. What is the correct way to do this?

Thanks,
Chad
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References: 
 >simultaneous parameter changes (From: Chad Wagner <email@hidden>)
 >Re: simultaneous parameter changes (From: William Stewart <email@hidden>)
 >Re: simultaneous parameter changes (From: Chad Wagner <email@hidden>)
 >Re: simultaneous parameter changes (From: Chad Wagner <email@hidden>)
 >Re: simultaneous parameter changes (From: Chad Wagner <email@hidden>)
 >Re: simultaneous parameter changes (From: William Stewart <email@hidden>)

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