AudioEngine used for TPI

AudioEngine.swift

//
//  AudioEngine.swift
//  TPI
//
//  Created by Stephen Radford on 29/05/2017.
//  Copyright © 2017 Cocoon Development Ltd. All rights reserved.
//

import Foundation
import AudioKit

class AudioEngine {
    
    static let shared = AudioEngine()
    
    var mic: AKMicrophone!
    var booster: AKBooster!
    var tracker: AKFrequencyTracker!
    var silence: AKBooster!
    var tap: AKFFTTap?
    var mixer: AKMixer
    
    private init() {
        AKSettings.audioInputEnabled = true
        
        // Shared by SPL + RTA
        mic = AKMicrophone()
        booster = AKBooster(mic)
        tracker = AKFrequencyTracker(booster)
        silence = AKBooster(tracker, gain: 0)
       
        // Tap for RTA
        tap = AKFFTTap(booster)
        mixer = AKMixer(silence, white, pink, sineOscillator, squareOscillator)
        
        AudioKit.output = mixer
        AudioKit.start()
        
        NotificationCenter.default.addObserver(self, selector: #selector(start), name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(stop), name: NSNotification.Name.UIApplicationDidEnterBackground, object: nil)
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationDidEnterBackground, object: nil)
    }
 
    @objc private func stop() {
        AudioKit.stop()
    }
    
    @objc private func start() {
        AudioKit.start()
    }
    
}