How to Change Audio Pitch During Playback? (Swift 4)

How to change audio pitch during playback? (Swift 4)

Actually, I got the answer from reddit. All I had to do was to declare the pitch and speed variables outside of the Play() function, along with the pitch.pitch = speedIncrement * (-500) and speed.rate = speedIncrement expressions. I knew I was missing something simple...

Swift change Pitch and Speed of recorded audio

Turns out this was simpler than I had thought using @AppStorage and conditionals to integrate the desired player. Thanks!

Changing the pitch of a sound in realtime (Swift)

If you use the Audio Unit API, the iOS built-in kAudioUnitSubType_NewTimePitch Audio Unit component can be used to change pitch while playing audio at the same speed. e.g. the kNewTimePitchParam_Rate and kNewTimePitchParam_Pitch parameters are independent.

The Audio Unit framework has a (currently non-deprecated) C API, but one can call C API functions from Swift code.

Changing Audio Pitch of sounder

You'll use the AVAudioEngine to attach the AVAudioPlayerNode to the AVAudioUnitTimePitch effect. I checked Apple's AudioUnitV3Example sample code and cobbled together a working example from it. You'll want to implement more state and error handling that you can find in there. Anyway, here goes:

Define some private variables at the top of your class:

   /// Playback engine.
    private let audioEngine = AVAudioEngine()

    /// Engine's player node.
    private let pitchPlayer = AVAudioPlayerNode()
    private let timePitch = AVAudioUnitTimePitch()

    /// File to play.
    private var audioFile: AVAudioFile?

Check for a valid audio file:

     override func viewDidLoad() {
         super.viewDidLoad()

     if let filePath = Bundle.main.path(forResource: "Sound1", ofType: 
 "mp3") {
         let filePathURL = URL(fileURLWithPath: filePath)

         setPlayerFile(filePathURL)

         }
     }

     private func setPlayerFile(_ fileURL: URL) {
         do {
             let file = try AVAudioFile(forReading: fileURL)

             self.audioFile = file

         } catch {
             fatalError("Could not create AVAudioFile instance. error: \(error).")
         }
     }

     @IBAction func verySlowPlayback(sender: UIButton) {

    timePitch.pitch = -300
    timePitch.rate = 0.5
    audioEngine.attach(pitchPlayer)
    audioEngine.attach(timePitch)

    audioEngine.connect(pitchPlayer, to: timePitch, format: audioFile?.processingFormat)
    audioEngine.connect(timePitch, to: audioEngine.outputNode, format: audioFile?.processingFormat)
    pitchPlayer.scheduleFile(audioFile!, at: nil, completionHandler: nil)

    // Start the engine.
    do {
        try audioEngine.start()
    } catch {
        fatalError("Could not start engine. error: \(error).")
    }

    pitchPlayer.play()

}

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