public void Start() {    if(_captureDevice == null)    {        requestStop = false;        //使用USB摄像机识别        _captureDevice = GetCaptureDevice();        //使用本地Resources目录下的720p.avi文件识别测试        //_captureDevice = GetFileVideoSource();        _captureDevice.NewFrame += _captureDevice_NewFrame; ;        _captureDevice.Start();    }}private void _captureDevice_NewFrame(object sender, NewFrameEventArgs eventArgs){    if (requestStop) return;    Bitmap newFrame = (Bitmap)eventArgs.Frame.Clone();    //如果使用视频文件请注释下面的这行代码，表示不对图像进行水平翻转    newFrame.RotateFlip(RotateFlipType.Rotate180FlipY);    lock (sync)    {        if (currentFrame != null)        {            currentFrame.Dispose();            currentFrame = null;        }        currentFrame = newFrame;        _fps.Invoke(sender, newFrame);    }}