openCV.cpp

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

using namespace std;
using namespace cv;

int main(int argc, char *argv[]){
     Mat server_img,client_img;
     VideoCapture cap("./video.mpg");
     
     // Get the resolution of the video
     int width = cap.get(CV_CAP_PROP_FRAME_WIDTH);
     int height = cap.get(CV_CAP_PROP_FRAME_HEIGHT);
     cout << "Video resolution: " << width << ", " << height << endl;
     
     // Allocate container to load frames 
     server_img = Mat::zeros(540, 960, CV_8UC3);
     client_img = Mat::zeros(540, 960, CV_8UC3);
     
     // Ensure the memory is continuous (for efficiency issue.)
     if(!server_img.isContinuous()){
          server_img = server_img.clone();
     }

     if(!client_img.isContinuous()){
          client_img = client_img.clone();
     }

     while(1){
          // Get a frame from the video to the container of the server.
          cap >> server_img;
          
          // Get the size of a frame in bytes 
          int imgSize = server_img.total() * server_img.elemSize();
          
          // Allocate a buffer to load the frame (there would be 2 buffers in the world of the Internet)
          uchar buffer[imgSize];
          
          // Copy a frame to the buffer
          memcpy(buffer, server_img.data, imgSize);
          
          // Here, we assume that the buffer is transmitted from the server to the client
          // Copy a fream from the buffer to the container of the client
          uchar *iptr = client_img.data;
          memcpy(iptr, buffer, imgSize);
          
          // show the frame 
          imshow("Video", client_img);  
          
          // Press ESC on keyboard to exit
          // Notice: this part is necessary due to openCV's design.
          // waitKey function means a delay to get the next frame. You can change the value of delay to see what will happen
          char c = (char)waitKey(33.3333);
          if(c==27)
               break;
     }

	cap.release();
	destroyAllWindows();
	return 0;
}