Is gstreamer disable the setting function of CAP_PROP_FOURCC?

C++
,
1

hi sir,
I have a webcam , its fps in 1280x720 is about 10 .
As I know that the fps can reach to 30 fps if I change VideoCapture’s input format to MJPG.

I used following code in opencv450 without gstreamer and It works fine, the fps in 1280x720 could be about 30

int main()
{
    VideoCapture video(0);
    std::cout << "MJPG: " << video.set(cv::CAP_PROP_FOURCC, cv::VideoWriter::fourcc('M', 'J', 'P', 'G'));
    video.set(CAP_PROP_FRAME_WIDTH,1280);
    video.set(CAP_PROP_FRAME_HEIGHT,720);
    cout<<"fps: "<< video.get(CAP_PROP_FPS)<<endl;
    
    Mat frame;
    while (video.isOpened()) {
        video>>frame;
        imshow("frame",frame);
        waitKey(1);
    }
    return 0;
}

Now I updated opencv to latest version (4.5.4) and build WITH_GSTREAMER, and the function

video.set(cv::CAP_PROP_FOURCC, cv::VideoWriter::fourcc('M', 'J', 'P', 'G'));

no longer works . it shows the message:

[ WARN:0] global /media/gino/a278e84d-9197-4f4e-8f2a-3a52677ef946/home/gino/opencv/opencv/modules/videoio/src/cap_gstreamer.cpp (1390) setProperty OpenCV | GStreamer warning: GStreamer: unhandled property

is that means gstreamer disable the CAP_PROP_FOURCC setting function? What should I do to make the correct setting?

2

Hi,

There is no such property in gstreamer binding in opencv

3

and no trace of it in 4.5.0, either

4

nothing indicates that your earlier test actually used gstreamer.

explicitly pass an apiPreference that is not gstreamer, to avoid using gstreamer.