opencv摄像头捕捉灰屏

一个简单的测试代码，但是显示窗口是灰屏的（使用电脑的摄像头）
win10，vs2017，opencv3.4.2

#include <cv.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main()
{
     CvCapture *capture = cvCreateCameraCapture(0);
        cvNamedWindow("myWindow", CV_WINDOW_AUTOSIZE);
        IplImage * frame;
        while (true)
        {
            frame = cvQueryFrame(capture);
            cvShowImage("myWindow", frame);
            char c = cvWaitKey(33);
            if (c == 27) break;
        }
        cvReleaseCapture(&capture);
        cvDestroyWindow("myWindow");
}

https://blog.csdn.net/bamboocan/article/details/70572789