Opencv VideoCapture实时捕捉摄像头信息

#include "opencv2/highgui/highgui.hpp"
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char* argv[])
{
    VideoCapture cap(); // open the video camera no. 0

    if (!cap.isOpened())  // if not success, exit program
    {
        cout << "Cannot open the video cam" << endl;
        return -;
    }

   double dWidth = cap.get(CV_CAP_PROP_FRAME_WIDTH); //get the width of frames of the video
   double dHeight = cap.get(CV_CAP_PROP_FRAME_HEIGHT); //get the height of frames of the video

    cout << "Frame size : " << dWidth << " x " << dHeight << endl;

    namedWindow("MyVideo",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"

    while ()
    {
        Mat frame;

        //bool bSuccess = cap.read(frame); // read a new frame from video

        // if (!bSuccess) //if not success, break loop
        //{
        //     cout << "Cannot read a frame from video stream" << endl;
        //     break;
        //}
        cap>>frame;
        imshow("MyVideo", frame); //show the frame in "MyVideo" window

        if (waitKey() == ) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
       {
            cout << "esc key is pressed by user" << endl;
            break;
       }
    }
    return ;

}

另外注明下，本人曾经想用手机来充当摄像头，利用DroidCam软件，但是貌似Opencv不支持这种方式，虽然运行代码后能够找到摄像头，但是始终无法正常显示图像，后来换了一个摄像头就完全可以正常显示了。不知道有哪位大大给解释下