Re: AudioUnit Events
Re: AudioUnit Events
- Subject: Re: AudioUnit Events
- From: Bjorn Roche <email@hidden>
- Date: Wed, 16 May 2007 16:00:25 -0400
On May 14, 2007, at 6:25 PM, Bjorn Roche wrote:
Hey there,
I am using Audio Unit events as described in technote 2104. I am a
bit confused about a few points:
1. What is the responsibility of the host when it changes
parameters, scheduling parameters and setting properties? In my
experiments, it seems that events fire automatically when I change
properties (as with OSStatus ret = AudioUnitSetProperty( ...
kAudioUnitProperty_PresentPreset, ... ) ), but NOT when I change
parameter values. I haven't tested scheduling parameters
extensively, but that doesn't seem to fire events either. My
conclusion is that I need to call AUEventListenerNotify after
changing a parameter, but not after changing a property. Is this
correct? What about scheduling changes?
Still not sure why AudioUnitSetProperty fires notification, but I've
added my own notification, just to be sure, and that seems to work.
2. How do I identify which events I fired, and which events
something else (e.g. the audio Unit GUI) fired? In the case of my
app, I have sliders that need to respond to changes in the AU, and
I want the AU to respond to changes in the slider, and I don't want
the two to keep firing events back and forth unnecessarily. I see
that AUEventListenerNotify has two parameters other than the event,
but as far as I can tell, they don't get passed on anywhere, and I
can't find docs on that. What am I missing?
Some searching through the mailing lists indicates events are not
"fired", nor are events queued, but rather changes are flagged and
listeners are updated through polling, so what I want is probably not
possible. I still don't know what those two parameters are for, but
many of the example code just uses NULL, and it's not documented
anywhere, so I'll presume it's for use in the future.
bjorn
-----------------------------
Bjorn Roche
XO Wave
Digital Audio Production and Post-Production Software
http://www.xowave.com
http://blog.bjornroche.com
http://myspace.com/xowave
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