VocalTract stops working when changing tenseness from 0 to 1

[maweibezahn]

macOS Version(s) Used to Build

macOS 13 Ventura

Xcode Version(s)

Xcode 14

Description

I am using macOS 15.4.1 and Xcode 16.3

When setting the tenseness parameter of VocalTract from 0 to 1, generation stops. This does not happen with any other value change (e.g. 0.001 to 1, 0 to 0.999 etc.). Other parameters work fine.

Steps to reproduce:

1. Create a simple project with an AudioEngine and a VocalTract as the output
2. Start the VocalTract with tenseness at 0
3. Change the tenseness to 1 (e.g. by the press of a button, or a timer)

Result:

Generation stops working, no sound.

Expected result:

The generation should not stop.

Proposed solution:

Maybe change the range in the parameter definition of tenseness to 0...0.999 (might be ugly but should work).

Crash Logs, Screenshots or Other Attachments (if applicable)

No response

[NickCulbertson]

import AudioKit
import AudioKitEX
import AudioKitUI
import AudioToolbox
import Combine
import SoundpipeAudioKit
import SwiftUI

class VocalTractConductor: ObservableObject, HasAudioEngine {
    let engine = AudioEngine()

    @Published var isPlaying: Bool = false {
        didSet { isPlaying ? voc.start() : voc.stop() }
    }

    var voc = VocalTract()

    init() {
        engine.output = voc
    }
}

struct Button2: View {
    var text: String
    var onTap: () -> Void

    var body: some View {
        ZStack {
            RoundedRectangle(cornerRadius: 10).foregroundColor(.gray)
            Text(text).onTapGesture {
                self.onTap()
            }
        }
    }
}

struct VocalTractView: View {
    @StateObject var conductor = VocalTractConductor()

    var body: some View {
        VStack {
            Text(conductor.isPlaying ? "STOP" : "START")
                .foregroundColor(.blue)
                .onTapGesture {
                conductor.isPlaying.toggle()
            }

            Button2(text: "Randomize") {
                conductor.voc.frequency = AUValue.random(in: 0 ... 2000)
                conductor.voc.tonguePosition = AUValue.random(in: 0 ... 1)
                conductor.voc.tongueDiameter = AUValue.random(in: 0 ... 1)
                conductor.voc.tenseness = AUValue.random(in: 0 ... 1)
                conductor.voc.nasality = AUValue.random(in: 0 ... 1)
            }
            
            Button2(text: "Toggle Tenseness") {
                if conductor.voc.tenseness > 0.5 {
                    conductor.voc.tenseness = 0
                }else{
                    conductor.voc.tenseness = 1
                }
            }

            HStack {
                ForEach(conductor.voc.parameters) {
                    ParameterRow(param: $0)
                }
            }.frame(height: 150)
            NodeOutputView(conductor.voc)
        }.cookbookNavBarTitle("Vocal Tract")
            .padding()
            .onAppear {
                conductor.start()
            }
            .onDisappear {
                conductor.stop()
            }
    }
}

When I put this into the Cookbook it seems to be working. What doesn't seem to be working however is setting the frequency to 0 but that is a separate issue. I'm on macOS 15.0.

[maweibezahn]

Here is an even more barebones, self contained, example which shows the behaviour that caused me to file this bug. I don't see anything wrong with it but am open for suggestions :)
Tested on a real device (iphone 15, iOS 18.4.1)

import SwiftUI
import SoundpipeAudioKit
import AudioKit

class Conductor: ObservableObject {
    
    let engine = AudioEngine()
    let vocalTract = VocalTract()
    
    init() {
        vocalTract.tenseness = 0
        engine.output = vocalTract
    }
    
    func start() {
        do {
            try engine.start()
            vocalTract.start()
        } catch {
            print(error)
        }
    }
    
}

struct ContentView: View {
    
    @StateObject var conductor = Conductor()
    
    var body: some View {
        VStack {
            Button("Set tenseness to 1") {
                conductor.vocalTract.tenseness = 1
            }
        }
        .onAppear {
            conductor.start()
        }
        .padding()
    }
}

#Preview {
    ContentView()
}

[NickCulbertson]

I moved that code into the Cookbook and was unable to recreate the issue on iPhone 12 Pro iOS 18.4, or on macOS. Then, when I created a new project with your code it DID recreate the bug. The error seems to show up when Settings.sampleRate == 48_000

[NickCulbertson]

Yeah, now after updating the Cookbook it is recreated in the Vocal Tract there too. SoundpipeBase is initialized with 44100 which I think might be the issue? I think setting the min values of problematic parameters is probably the best workaround for now. Tenseness and Frequency need to be > 0.

[maweibezahn]

It gets even more interesting: I made a macOS app (native not Catalyst) with the code above which works perfectly fine when the sampleRate is 48k. And I first encountered this problem in a Catalyst app which runs at 44.1k
For my app I indeed resorted to the workaround of limiting tenseness to 0.99 :)