micconfig.swift

private func configureMicrophone() -> Bool {
    session.beginConfiguration()
    defer {
      session.commitConfiguration()
    }

    session.usesApplicationAudioSession = true
    session.automaticallyConfiguresApplicationAudioSession = false

    do {
      try AVAudioSession.sharedInstance().setCategory(.playAndRecord, options: .allowBluetooth)
      try AVAudioSession.sharedInstance().setActive(true)
    } catch  {
      print("Error messing with audio session: \(error)")
    }


    if let availableInputs = AVAudioSession.sharedInstance().availableInputs {
      print("Found \(availableInputs.count) inputs")
      let selectedInput: AVAudioSessionPortDescription
      if let usbInput = availableInputs.first(where:{ $0.portType == .usbAudio }) {
        selectedInput = usbInput
      } else if let lineInput = availableInputs.first(where:{ $0.portType == .lineIn }) {
        selectedInput = lineInput
      } else if let micInput = availableInputs.first(where:{ $0.portType == .headsetMic }) {
        selectedInput = micInput
      } else if let bluetoothInput = availableInputs.first(where:{ $0.portType == .bluetoothHFP }) {
        selectedInput = bluetoothInput
      } else if let builtInInput = availableInputs.first(where:{ $0.portType == .builtInMic }) {
        selectedInput = builtInInput
      } else {
        fatalError("could not find a suitable input")
      }

      print("setting preferred input \(selectedInput)")
      do {
        try AVAudioSession.sharedInstance().setPreferredInput(selectedInput)
      } catch {
        print("Error setting preferred input: \(error)")
      }
    }

    // Find the microphone
    guard let microphone = AVCaptureDevice.default(for: .audio) else {
      print("Could not find the microphone")
      return false
    }

    // Add the microphone input to the session
    do {
      microphoneDeviceInput = try AVCaptureDeviceInput(device: microphone)
      
      guard let microphoneDeviceInput = microphoneDeviceInput,
        session.canAddInput(microphoneDeviceInput) else {
          print("Could not add microphone device input")
          return false
      }
      session.addInputWithNoConnections(microphoneDeviceInput)
    } catch {
      print("Could not create microphone input: \(error)")
      return false
    }
    
    // Find the audio device input's back audio port
    guard let microphoneDeviceInput = microphoneDeviceInput,
      let backMicrophonePort = microphoneDeviceInput.ports(
        for: .audio,
        sourceDeviceType: microphone.deviceType,
        sourceDevicePosition: .back).first else {
          print("Could not find the back camera device input's audio port")
          return false
    }

    // Find the audio device input's front audio port
    guard let frontMicrophonePort = microphoneDeviceInput.ports(
      for: .audio,
      sourceDeviceType: microphone.deviceType,
      sourceDevicePosition: .front).first else {
        print("Could not find the front camera device input's audio port")
        return false
    }
    
    // Add the back microphone audio data output
    guard session.canAddOutput(backMicrophoneAudioDataOutput) else {
      print("Could not add the back microphone audio data output")
      return false
    }

    if frontMicrophonePort == backMicrophonePort {
      print("front and back mic ports are the SAME!")
    }
    session.addOutputWithNoConnections(backMicrophoneAudioDataOutput)
    backMicrophoneAudioDataOutput.setSampleBufferDelegate(self, queue: dataOutputQueue)
    
    // Add the front microphone audio data output
    guard session.canAddOutput(frontMicrophoneAudioDataOutput) else {
      print("Could not add the front microphone audio data output")
      return false
    }
    session.addOutputWithNoConnections(frontMicrophoneAudioDataOutput)
    frontMicrophoneAudioDataOutput.setSampleBufferDelegate(self, queue: dataOutputQueue)

    // Connect the back microphone to the back audio data output
    let backMicrophoneAudioDataOutputConnection = AVCaptureConnection(inputPorts: [backMicrophonePort], output: backMicrophoneAudioDataOutput)
    guard session.canAddConnection(backMicrophoneAudioDataOutputConnection) else {
      print("Could not add a connection to the back microphone audio data output")
      return false
    }
    session.addConnection(backMicrophoneAudioDataOutputConnection)
    
    // Connect the front microphone to the back audio data output
    let frontMicrophoneAudioDataOutputConnection = AVCaptureConnection(inputPorts: [frontMicrophonePort], output: frontMicrophoneAudioDataOutput)
    guard session.canAddConnection(frontMicrophoneAudioDataOutputConnection) else {
      print("Could not add a connection to the front microphone audio data output")
      return false
    }
    session.addConnection(frontMicrophoneAudioDataOutputConnection)

    return true
  }