Open Radar

 
Running an iOS via Catalyst on a Mac using built-in mic & speaker, AVAudioSession always reports the inputLatency as 0.

private func initAudioSession() {
    do {
        audioSession = AVAudioSession()
        try audioSession.setCategory(.playAndRecord, options: [.allowBluetooth, .allowBluetoothA2DP, .defaultToSpeaker])

        let builtInTypes: [AVAudioSession.Port] = [.lineIn, .builtInMic]
        let connectedTypes: [AVAudioSession.Port] = [.headsetMic, .usbAudio, .bluetoothHFP]

        guard let inputs = audioSession.availableInputs else {
            preconditionFailure()
        }
        
        var input: AVAudioSessionPortDescription!
        
        // Prefer airpods/headphones if connected
        if let connectedInput = (inputs.first { connectedTypes.contains($0.portType) }) {
            input = connectedInput
        }
        if input == nil {
            if let builtInInput = (inputs.first { builtInTypes.contains($0.portType) }) {
                input = builtInInput
            }
        }

        precondition(input != nil)
                    
        try audioSession.setPreferredInput(input)
        try audioSession.setActive(true)
    } catch {
        assertionFailure("*** Caught: \(error)")
    }
}

At some point during the capture session:

func printLatencyInfo() {
    print("audioSession.inputLatency: \(audioSession.inputLatency)")
    print("audioSession.outputLatency: \(audioSession.outputLatency)")
    print("audioSession.ioBufferDuration: \(audioSession.ioBufferDuration)")
    print("engine.mainMixerNode.auAudioUnit.latency: \(engine.mainMixerNode.auAudioUnit.latency)")
    print("engine.inputNode.auAudioUnit.latency: \(engine.inputNode.auAudioUnit.latency)")
    print("engine.outputNode.auAudioUnit.latency: \(engine.outputNode.auAudioUnit.latency)")
    print("engine.mainMixerNode.outputPresentationLatency: \(engine.mainMixerNode.outputPresentationLatency)")
    print("engine.inputNode.outputPresentationLatency: \(engine.inputNode.outputPresentationLatency)")
    print("engine.outputNode.outputPresentationLatency: \(engine.outputNode.outputPresentationLatency)")
    print("engine.inputNode.auAudioUnit.latency: \(engine.inputNode.auAudioUnit.latency)")
    print("engine.outputNode.auAudioUnit.latency: \(engine.outputNode.auAudioUnit.latency)")
    print("metronomePlayerNode.auAudioUnit.latency: \(metronomePlayerNode.auAudioUnit.latency)")
}

And here audioSession.inputLatency is always 0 on Mac Catalyst with built-in mic & speaker.