Misery (Continued)

So the best I can do to fix the NSLog() and breakpoint problem on this particular project (or a project using the same file, i.e., another independently constructed duplicate project) is to diddle the Code Signing settings for "Any iOS" between "iPhone Developer" and "iPhone Developer: me XXXXXX".

Good news on the audio front...

It turns out that when you instantiate an AudioUnit the settings of "[ AVAudioSession sharedInstance] setCategory:" matter. 

For example, with the category set to "AVAudioSessionCategoryPlayback" you can instantiate an AudioUnit with input but the render loop will not be called.  Changing the category to "AVAudioSessionCategoryPlayAndRecord" after instantiation does not change this - even if you stop and restart the AudioUnit. 

So if you don't use the Record category your render loop will simply not be called.

I have been looking around at various documentation for AudioUnits wonder what you are allowed to do and not do with multiple AudioUnits simultaneously.  Certainly it seems you should be able to have more than one at any given time and in fact as long as they don't overlap on input and output and you have the right category set on instantiation this seems to be true from my experiments.

But there is little documentation of this - at least I could not find it.

AudioUnits and AVAudioPlayer do not work well together either.  However, I probably did not have the categories set properly so this might be part of the cause though some other testing leads me to believe there are other incompatibilities.

Basically I eliminated AVAudioPlayer as well as some other MixerHostAudio code I was using.  I now do my own mixing and sound triggering in a pair of AudioUnits and it seems far simpler and more efficient.