/// <summary>
    ///   This method shows the CheckVideoDeviceCount API call.  It should only be used
    //  after EnableVideo() call.
    /// </summary>
    /// <param name="engine">Video Engine </param>
    void CheckDevices(IRtcEngine engine)
    {
        VideoDeviceManager deviceManager = VideoDeviceManager.GetInstance(engine);

        deviceManager.CreateAVideoDeviceManager();

        int cnt = deviceManager.GetVideoDeviceCount();

        Debug.Log("Device count =============== " + cnt);
    }
    void GetVideoDeviceManager()
    {
        string videoDeviceName = "";
        string videoDeviceId   = "";

        /// If you want to getVideoDeviceManager, you need to call startPreview() first;
        mRtcEngine.StartPreview();
        videoDeviceManager = (VideoDeviceManager)mRtcEngine.GetVideoDeviceManager();
        videoDeviceManager.CreateAVideoDeviceManager();
        int count = videoDeviceManager.GetVideoDeviceCount();

        logger.UpdateLog(string.Format("VideoDeviceManager count: {0}", count));
        for (int i = 0; i < count; i++)
        {
            videoDeviceManager.GetVideoDevice(i, ref videoDeviceName, ref videoDeviceId);
            videoDeviceManagerDic.Add(i, videoDeviceId);
            logger.UpdateLog(string.Format("VideoDeviceManager device index: {0}, name: {1}, id: {2}", i, videoDeviceName, videoDeviceId));
        }
    }