I am trying to transfer a USB camera stream using Opencv VideoWriter to get it on another pc over UART using VideoCapture. However, I am stuck on VideoWriter. Execution of this code returns with an error and out.isOpened () is always false.
The code that I use…

  VideoWriter outputVideo(
    "appsrc ! videoconvert ! videoscale ! video/x-raw,width=640,height=480 !x264enc !fakesink ",
    0,
    20,
    Size(800, 600),
    true);

if (!outputVideo.isOpened()) {
    cerr << "VideoWriter not opened" << endl;
    exit(-1);
}

How can I solve this issue?