OpenCV —— Calling Cameras

Before you call two or more camera You have got to ensure the cameras to use different HUB!

//Here hide some headers and common callings
int main()
{
    VideoCapture cap(0);
    while(1)
    {
        Mat frame;
        cap >> frame;
        imshow("camera",frame);
        if(waitKey(0) == 27)break;
    }
    return 0;
}

If you want to use more usb-cameras to show image,you just need to replace cap(0) with cap(1)(take two cameras for example).And you also need to call one more Mat variary to receive the data-stream.