Swift: Sound-Output & Microphone-Input | using AudioKit |

Question

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I'm using>Xcode Version 9.2<
I'm using>AudioKit Version 4.0.4<

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I've written some code you can find below that should be able to

• play a specific sound (frequency: 500.0HZ)
• "listen" to the microphone input and calculating the frequency in real time

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If I'm calling playSound() or receiveSound() separated everything looks fine and is really working as I expected. But calling playSound() and receiveSound() afterwards? Exactly there I got big issues.

This is how I'd like to get the code working:

SystemClass.playSound() //play sound
DispatchQueue.main.asyncAfter(deadline: (DispatchTime.now() + 3.0)) {
 SystemClass.receiveSound() //get microphone input 3 seconds later
}

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let SystemClass: System = System()
class System {
 public init() { }
 func playSound() {
 let sound = AKOscillator()
 AudioKit.output = sound
 AudioKit.start()
 sound.frequency = 500.0
 sound.amplitude = 0.5
 sound.start()
 DispatchQueue.main.asyncAfter(deadline: (DispatchTime.now() + 2.0)) {
 sound.stop()
 }
 }
 var tracker: AKFrequencyTracker!
 func receiveSound() {
 AudioKit.stop()
 AKSettings.audioInputEnabled = true
 let mic = AKMicrophone()
 tracker = AKFrequencyTracker(mic)
 let silence = AKBooster(tracker, gain: 0)
 AudioKit.output = silence
 AudioKit.start()
 Timer.scheduledTimer( timeInterval: 0.1, target: self, selector: #selector(SystemClass.outputFrequency), userInfo: nil, repeats: true)
 }
 @objc func outputFrequency() {
 print("Frequency: \(tracker.frequency)")
 }
}

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These messages are some of the compiler error-messages I get every time I'd like to run the code (calling playSound() and calling receiveSound () 3 seconds later):

AVAEInternal.h:103:_AVAE_CheckNoErr: [AVAudioEngineGraph.mm:1266:Initialize: (err = AUGraphParser::InitializeActiveNodesInOutputChain(ThisGraph, kOutputChainOptimizedTraversal, *GetOutputNode(), isOutputChainActive)): error -10875
AVAudioEngine.mm:149:-[AVAudioEngine prepare]: Engine@0x1c401bff0: could not initialize, error = -10875
[MediaRemote] [AVOutputContext] WARNING: AVF context unavailable for sharedSystemAudioContext
[AVAudioEngineGraph.mm:1266:Initialize: (err = AUGraphParser::InitializeActiveNodesInOutputChain(ThisGraph, kOutputChainOptimizedTraversal, *GetOutputNode(), isOutputChainActive)): error -10875
Fatal error: AudioKit: Could not start engine. error: Error 
Domain=com.apple.coreaudio.avfaudio Code=-10875 "(null)" UserInfo={failed call=err = AUGraphParser::InitializeActiveNodesInOutputChain(ThisGraph, kOutputChainOptimizedTraversal, *GetOutputNode(), isOutputChainActive)}.: file /Users/megastep/src/ak/AudioKit/AudioKit/Common/Internals/AudioKit.swift, line 243

Answer 1

I believe the lionshare of your problems are due to local declaration of AKNodes within the functions that use them:

 let sound = AKOscillator()
 let mic = AKMicrophone() 
 let silence = AKBooster(tracker, gain: 0)

Declare these as instance variables instead, as described here.

• tsuyoski: Were you able to accomplish what you wrote in the question (playing sounds and receiving sounds)? I want to do the same thing, but it's just crashing.