AudioKit crashes

Question

I'm trying to create an app that:

1. Records my microphone and saves the output to a file
2. Plays the last recorded file
3. The playback should be manipulated with effects such as pitch-shift

So far I've got 1+2 down, but when I try to assign the AudioKit.output to my timePitch (or PitchShifter for that matter), I get an exception (see below). Can anyone help me out? Seems like if I set output to anything else than player, it crashes..

Disclaimer: I'm new to Swift, so please go easy on me and forgive my bad code

2017-11-08 16:39:58.637075+0100 mysoundplayer[41113:759865] *** Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'player started when in a disconnected state'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000108a3c1ab __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x00000001047ddf41 objc_exception_throw + 48
    2   CoreFoundation                      0x0000000108a41372 +[NSException raise:format:arguments:] + 98
    3   AVFAudio                            0x000000010b3bb00e _Z19AVAE_RaiseExceptionP8NSStringz + 158
    4   AVFAudio                            0x000000010b4131ce _ZN21AVAudioPlayerNodeImpl9StartImplEP11AVAudioTime + 204
    5   AVFAudio                            0x000000010b412482 -[AVAudioPlayerNode playAtTime:] + 82
    6   AudioKit                            0x0000000103a2270d _T08AudioKit13AKAudioPlayerC4playySo11AVAudioTimeCSg2at_tFTf4gn_n + 1933
    7   AudioKit                            0x0000000103a1c78d _T08AudioKit13AKAudioPlayerC5startyyF + 45
    8   mysoundplayer                          0x00000001035dd3b8 _T010mysoundplayer14ViewControllerC14playLoadedFileyyF + 1832
    9   mysoundplayer                          0x00000001035dca1e _T010mysoundplayer14ViewControllerC4playySo8UIButtonCF + 46
    10  mysoundplayer                          0x00000001035dca6c _T010mysoundplayer14ViewControllerC4playySo8UIButtonCFTo + 60
    11  UIKit                               0x000000010507c275 -[UIApplication sendAction:to:from:forEvent:] + 83
    12  UIKit                               0x00000001051f94a2 -[UIControl sendAction:to:forEvent:] + 67
    13  UIKit                               0x00000001051f97bf -[UIControl _sendActionsForEvents:withEvent:] + 450
    14  UIKit                               0x00000001051f81e7 -[UIControl touchesBegan:withEvent:] + 282
    15  UIKit                               0x00000001050f1916 -[UIWindow _sendTouchesForEvent:] + 2130
    16  UIKit                               0x00000001050f32de -[UIWindow sendEvent:] + 4124
    17  UIKit                               0x0000000105096e36 -[UIApplication sendEvent:] + 352
    18  UIKit                               0x00000001059d9434 __dispatchPreprocessedEventFromEventQueue + 2809
    19  UIKit                               0x00000001059dc089 __handleEventQueueInternal + 5957
    20  CoreFoundation                      0x00000001089df231 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    21  CoreFoundation                      0x0000000108a7ee41 __CFRunLoopDoSource0 + 81
    22  CoreFoundation                      0x00000001089c3b49 __CFRunLoopDoSources0 + 185
    23  CoreFoundation                      0x00000001089c312f __CFRunLoopRun + 1279
    24  CoreFoundation                      0x00000001089c29b9 CFRunLoopRunSpecific + 409
    25  GraphicsServices                    0x000000010cc289c6 GSEventRunModal + 62
    26  UIKit                               0x000000010507a5e8 UIApplicationMain + 159
    27  mysoundplayer                          0x00000001035e12a7 main + 55
    28  libdyld.dylib                       0x000000010aa49d81 start + 1
    29  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Source code:

import AudioKit
import AudioKitUI
import UIKit

class ViewController: UIViewController {

var micMixer: AKMixer!
var recorder: AKNodeRecorder!
var player: AKAudioPlayer!
var tape: AKAudioFile!
var timePitch: AKTimePitch!
var pitchShifter: AKPitchShifter!
var mainMixer : AKMixer!
var loadedFile: AKAudioFile!

let mic = AKMicrophone()

var state = State.readyToRecord

enum State {
    case readyToRecord
    case recording
    case readyToPlay
    case playing
}

@IBAction func toggleRecord(_ sender: UIButton) {
    switch state {
    case .recording:
        sender.setTitle("record", for: .normal)
        state = .readyToRecord
        do {
            try player.reloadFile()
        } catch {
            print("Error reloading!")
        }

        let recordedDuration = player != nil ? player.audioFile.duration : 0
        if recordedDuration > 0.0 {
            recorder.stop()
            let randomfilename:String = NSUUID().uuidString + ".m4a"
            print("Filename: \(randomfilename)")
            player.audioFile.exportAsynchronously(name: randomfilename, baseDir: .documents, exportFormat: .m4a, callback: {file, exportError in
                if let error = exportError {
                    print("Export failed \(error)")
                } else {
                    print("Export succeeded")
                    self.loadedFile = file
                }
            })
        }
    case .readyToRecord:
        do {
            try recorder.record()
            sender.setTitle("stop", for: .normal)
            state = .recording
        } catch { print("Error recording!") }

    default:
        print("no")
    }
}


@IBAction func play(_ sender: UIButton) {
    playLoadedFile()
}

@IBAction func valueChanged(_ sender: UISlider) {
    timePitch.pitch = Double(sender.value)
}

func playLoadedFile() {
    do {
        try player.replace(file: loadedFile)
        player.start()
    } catch { print("Error playing!") }
}

func exportedAudioFile(filename: String) {
    print("yay")
}

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view, typically from a nib.

    AKAudioFile.cleanTempDirectory()
    AKSettings.bufferLength = .medium
    AKSettings.defaultToSpeaker = true

    //inputPlot.node = mic
    micMixer = AKMixer(mic)
    mainMixer = AKMixer(player,timePitch)

    pitchShifter = AKPitchShifter(player)
    timePitch = AKTimePitch(player)

    recorder = try? AKNodeRecorder(node: micMixer)
    if let file = recorder.audioFile {
        player = try? AKAudioPlayer(file: file)
    }

    AudioKit.output = timePitch // works with player
    AudioKit.start()
    print("mainMixer status: \(mainMixer.isStarted)")


}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

Answer 1

It looks like mainMixer isn't connected to anything. Try changing AudioKit.output = timePitch to AudioKit.output = mainMixer .

As for best practices, get rid of any try? s. Use a do try catch and at least print the error.

if let file = recorder.audioFile {
    do{
        player = try AKAudioPlayer(file: file)
    } catch {
        print(error)
    }
}

Answer 2

You're attaching the player to the mixer before you create it. At the time where you give player to AKMixer(), it is nil. Move the mixer creation after the player assignment.