AudioKit crashes - ios

Question

I'm trying to create an app that:
Records my microphone and saves the output to a file
Plays the last recorded file
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.