VideoWriter out;

void udp_start_video_writer (void)
{
    out.open("appsrc ! videoconvert ! x264enc tune=zerolatency byte-stream=true threads=4 ! mpegtsmux ! udpsink host=192.168.1.98 port=1234",
            VideoWriter::fourcc('X','2','6','4'),
            30.0,
            Size(UDPDATA_FRAME_WIDTH, UDPDATA_FRAME_HEIGHT),
            true);
}

int main(){
    // Some initializations...
    while(1) {
    // Create an image to hold initial frame data
      Mat PrScr(UDPDATA_FRAME_WIDTH, UDPDATA_FRAME_HEIGHT, CV_8UC(4));

      // PrScr frame is read here...
      // ....
      // ....

      if(PrScr.size().width!=0 && out.isOpened()) // skip errorneous data
      {
        // Rotate image
        cv::rotate(PrScr, PrScr, cv::ROTATE_180);

        // Change image's color space
        cv::cvtColor(PrScr, PrScr, cv::COLOR_RGB2BGR);

        //Write image to VideoWriter's output (piped through gstreamer)
        out.write(PrScr);
      }
   }
}

VideoCapture video_input
video_input.open("udpsrc port=1234 ! tsparse ! tsdemux ! h264parse ! avdec_h264 ! videoconvert ! appsink", cv::CAP_GSTREAMER);

gst-launch-1.0 udpsrc port=1234 ! tsparse ! tsdemux ! h264parse ! avdec_h264 ! videoconvert ! appsink