Inter-app Audio and AVAudioEngine?

Hi Michael,

Be really interested to hear if you made any headway on this as I'm in a similar situation as of yesterday. I've managed to publish my AU so it shows up in IAA apps as an instrument but no luck re-routing the audio to the host thus far. I'm getting the route change notification when the IAA host discovers my app, but Im kinda scratching around figuring how to deal with it.

Documentation / examples are you probably know are very hard to find and there's virtually no Swift examples. Seems like crossing the border from AVFoundation to Core Audio isn't as straightforward as you'd hope it might be! :-)

Cheers, -Rob

edit - I'm going to ask this question over on the AVFoundation and see if we get any luck there.

Hi Michael,

I'm using 3rd party audio libraries for playing,recording etc for host app. This libraries hard to integrate with IAA.

I see your post when i was searching AVAudioEngine. If you succeed integrating AVAudioEngine with IAA or if you have found any clue to do this

i'll change my audio engine to AVAudioEngine.

Thanks

Umut

FWIW, I got this working in Swift without any 3rd-party libraries, but I have to say getting the IAA host property change notification (AudioUnitAddPropertyListener) to work was not pretty. If you're not familiar with dealing with UnsafeMutableRawPointers and bridging between Swift classes and C functions, I'd suggest you don't go there... -Rob

Hi Rob,

That's exactly the problem I'm having. I've coded my app in Swift 3 and want

to use IAA. I was following an objective C tutorial on doing this and got

stuck on the UnsafeMutableRawPointers, specifically the fourth parameter to

AudioOutputUnitPublish, inOutputUnit.

It would be a great help if you have some example code to share. I might be

able to figure it out from there.

Cheers Matt,

Well, this is a super old post, but I just figured out one (possibly terrible) way of doing this by creating a semaphore and passing around pointers...

        var sem = DispatchSemaphore(value: 0)
        DispatchQueue.global(qos: .background).async {
            while true {
                sem.wait()
               
                do {
                    try AVAudioSession.sharedInstance().setActive(true)
                    try self.engine.start()
                }
                catch {
                    print("unable to start Audio Engine!!!: \(error)")
                }
            }
        }
       
        let proc: AudioUnitPropertyListenerProc = { (inRefCon, inUnit, inID, inScope, inElement) in
            let sem = inRefCon.assumingMemoryBound(to: DispatchSemaphore.self).pointee
            sem.signal()
        }
       
        AudioUnitAddPropertyListener(self.engine.outputNode.audioUnit!,kAudioUnitProperty_IsInterAppConnected, proc,UnsafeMutableRawPointer(&sem))