Swift 自定义摄像头，当我用后置摄像头录制视频时，视频不会与音频一起播放

我试图使定制相机工作得很好，但当我把相机切换到后位置时，视频正在录制，但没有声音，当我换到前位置时，它工作得很好，这是我的全部代码。如果有人能帮我，我真的很感激

    ` func changeCamera(){

    guard let input = session!.inputs[0] as? AVCaptureDeviceInput else { return }

        // Begin new session configuration and defer commit
    session!.beginConfiguration()
       defer { session!.commitConfiguration() }
        // Create new capture device
        var newDevice: AVCaptureDevice?

        if input.device.position == .back {

            newDevice = cameraWithPosition(position: .front)

        }else{
            newDevice = cameraWithPosition(position: .back)

    }

//创建新的捕获输入 var设备输入：AVCaptureDeviceInput

        do {
            deviceInput = try AVCaptureDeviceInput(device: newDevice!)
        } catch let error {
            print(error.localizedDescription)
            return
        }

        //session!.removeInput(input)
    if let inputs = session!.inputs as? [AVCaptureDeviceInput] {
        for input in inputs {
            session!.removeInput(input)

        }
    }

            session!.addInput(deviceInput)
    }

    func cameraWithPosition(position: AVCaptureDevice.Position) -> AVCaptureDevice? {

     let deviceDescoverySession = AVCaptureDevice.DiscoverySession.init(deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera],                                                                             mediaType: AVMediaType.video,position: AVCaptureDevice.Position.unspecified)
       for device in deviceDescoverySession.devices {
            if device.position == position {
                return device
            }
        }
   return nil
     }`