EMGU CV C＃从USB摄像头捕获而不是内置网络摄像头

Question

这是代码：

public partial class Form1 : Form
{
    private Capture _capture = null;
    private Image<Bgr, Byte> frame;

    public Form1()
    {
        InitializeComponent();
    }

    private void captureFrame(object sender, EventArgs e)
    {
        //frame = _capture.QueryFrame();

        frame = _capture.RetrieveBgrFrame();

        Bgr color = frame[10,10];

        Byte blue = (Byte)color.Blue;
        Byte red = (Byte)color.Red;
        Byte green = (Byte)color.Green;

        pictureBox1.Image = frame.ToBitmap();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        //-> Create a List to store for ComboCameras
        List<KeyValuePair<int, string>> ListCamerasData = new List<KeyValuePair<int, string>>();

        //-> Find systems cameras with DirectShow.Net dll
        DsDevice[] _SystemCamereas = DsDevice.GetDevicesOfCat(FilterCategory.VideoInputDevice);

        int _DeviceIndex = 0;
        foreach (DirectShowLib.DsDevice _Camera in _SystemCamereas)
        {
            ListCamerasData.Add(new KeyValuePair<int, string>(_DeviceIndex, _Camera.Name));
            _DeviceIndex++;
        }

        if (button1.Text == "PLAY")
        {
            _capture = null;
            _capture = new Capture(0);

_capture.SetCaptureProperty(Emgu.CV.CvEnum.CAP_PROP.CV_CAP_PROP_FPS, 30);


_capture.SetCaptureProperty(Emgu.CV.CvEnum.CAP_PROP.CV_CAP_PROP_FRAME_HEIGHT, 480);

_capture.SetCaptureProperty(Emgu.CV.CvEnum.CAP_PROP.CV_CAP_PROP_FRAME_WIDTH, 640);

            button1.Text = "STOP";

            Application.Idle += captureFrame;
        }
        else
        {
            Application.Idle -= captureFrame;

            button1.Text = "PLAY";

            _capture.Stop();

            if (_capture != null)
                _capture.Dispose();


        }

    }
}

在ListCamerasData中我可以看到2个摄像头0 - 来自笔记本电脑的摄像头和1 - SMI Video Grabber。

如果我更改_capture = new Capture（0）; ==＆GT;＆GT; _capture = new Capture（1）;洞程序冻结了。

如何从相机SMI视频Grabber中捕获？