Create an RTP stream from a webcam with OpenCV and GStreamer

opencv_capture_to_rtp_stream.cpp

#include <opencv2/opencv.hpp>

int main( int argc, char ** argv )
{
  cv::VideoCapture cap;
  cv::Mat frame;

  const std::string windowName{ "RTP Stream" };
  cap.open( 0 );
  cap.set( cv::CAP_PROP_FRAME_WIDTH, 640 );
  cap.set( cv::CAP_PROP_FRAME_HEIGHT, 480 );
  cv::VideoWriter outputVideo( "appsrc ! videoconvert ! x264enc tune=zerolatency bitrate=500 speed-preset=superfast ! rtph264pay ! udpsink host=127.0.0.1 port=5000",
                               cv::CAP_GSTREAMER,
                               0,
                               30,
                               cv::Size( 640, 480 ) );

  for( cap >> frame; !frame.empty(); cap >> frame )
  {
    cv::imshow( windowName, frame );
    outputVideo.write( frame );

    char key = cv::waitKey( 1 );
    if( key == 'q' || key == 27 )
      break;
  }

  cv::destroyWindow( windowName );
}

// open with:
//   gst-launch-1.0 -v udpsrc port=5000 caps = "application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, payload=(int)96" ! rtph264depay ! decodebin ! videoconvert  ! xvimagesink sync=0