AUAudioUnit issues with V2 plugins

Hello,

I am currently writing plug-in hosting code for my iOS/OSX app and I am using the new AudioUnit V3 API.

My app is capable of hosting both instruments and effects. I already have implemented this using the V2 API (OSX "classic AU", and iOS IAA) in the past with success. All is written in C++ so I use the Obj-C interface.

I am able to instanciate V2 effects (iOS/OSX) & V3 effects (iOS "FilterDemo") and use them without any issue.

However, some V2 instruments will fail to instanciate (error -3000) on OSX. I cannot test this on iOS 9 since no AU instruments are available to this day.

To instanciate and use an instrument, I do the following.

Note that my effect instanciation/configuration code is similar (I just enable the inputBusses[0] and provide a AURenderPullInputBlock to the renderBlock).

• Instanciate the AudioUnit from its AudioComponentDescription using:

[AUAudioUnit instantiateWithComponentDescription:desc
                                        options:kAudioComponentInstantiation_LoadOutOfProcess
                                  completionHandler:^ (AUAudioUnit * __nullable audioUnit, NSError * __nullable error
{ // here is the code that will configure the returned AUAudioUnit }

• When the completion handler is called, I setup the the AUAudioUnit:

// Set maximum frames

pAUAudioUnit.maximumFramesToRender = ...;

// check the format from pAUAUdioUnit.outputBusses[0].format; etc. [stripped] 

// Allocate resources
if ([pAVAudioUnit.AUAudioUnit allocateRenderResourcesAndReturnError:&nserr] == NO) {
  // error handling
}

// Cache the renderBlock property
pInstance->mpRenderBlock = pAudioUnit.AUAudioUnit.renderBlock;

• Then, when I need to render the AudioUnit

err = mpInstance->mpRenderBlock(&f, &mAUTime, frames, 0, mpAUBuffers, nil /*effects would pass the input block here*/);

On iOS, I cannot effect instruments because none are available.

On OSX (10.11 BETA 6), I can instanciate and use AUSampler, AUAudioFilePlayer, but instruments like Kontakt 5 or Massive won't load.

I get this error in the completionHandler after using instantiateWithComponentDescription.

Cannot async instantiate component: The operation couldn’t be completed. (OSStatus error -3000.)

Also, apparently the

kAudioComponentInstantiation_LoadInProcess / kAudioComponentInstantiation_LoadOutOfProcess

option passed to the

+[AUAudioUnit instantiateWithComponentDescription:...]

has an impact on the result.

So my question is pretty simple: in its current state, is this normal to have these kind of errors while instanciating older, V2 3rd party instrument AudioUnits ?

I remember being able to instanciate V2 instruments with the V3 API using:

+[AVAudioUnit instantiateWithComponentDescription:...]

However, I am not using an AVAudioEngine so it does not make sense to use an AVAudioUnit (which is an AVAudioNode); this also does not work for effects in my case since they are not connected to a graph (ie: no connection error).

Some confirmation on the current state of the V3 implementation on both iOS and OSX would be appreciated.

Thank you !

Mathieu.