#include <iostream>

#include <opencv2/opencv.hpp>

using namespace cv;

using namespace std;

int main()

{

        Mat input_image;

        VideoCapture cam(0);

        if (!cam.isOpened()) exit(0);

        Size s(320, 240);

        VideoWriter writer = VideoWriter("myvideo.avi", CV_FOURCC('M', 'J', 'P', 'G'), 25, s);

        if (!writer.isOpened())

        {

                cout << "cannot create a file.\n" << endl;

                return -1;

        }

        namedWindow("input image");

        while (true) {

                cam >> input_image;

                //WriteFrame(writer, outimage)

//                cvWriteFrame(writer, input_image);

                imshow("input image", input_image);

//                writer << input_image;

                if (27 == waitKey(30))

                        break;

        }

       

}=====3.0里面是这个 函数 视频帧  cam >> input_image;