Display an video flux from libcamera and gstreamer to an Java JFrame

Question

I need your help for an libcamera, gstreamer and java issue.

I trie to display the libcamera video flux from a Pi Cam v3 connected to an Pi Zero 2 W to an Java JFrame on PC to order a rover. Minimal latency is the key !

I found how to do with CLI :

libcamera-vid -t 0 --nopreview --width 1280 --height 720 --framerate 60 --vflip --hflip --autofocus-mode auto --codec mjpeg -o - | gst-launch-1.0 fdsrc fd=0 ! udpsink host=192.168.5.127 port=5000

and for the receiver :

gst-launch-1.0 udpsrc port=5000 ! jpegparse ! jpegdec ! queue ! autovideosink

I have low latency like I desire. Exquisite !

!! BUT !!

Now, I have to integrate the receiver in a java app. And there ... I have a little ... tiny ... problem.

I see on my task manager network activities when I launch the app but the JFrame screen juste stay definitly black.

public class GstreamerFrame {

    private static Pipeline pipeline;
    private static JFrame frame;
    
    public static void main(String[] args) {
        Utils.configurePaths();
        Gst.init(Version.BASELINE, "BasicPipeline");
    
        pipeline = (Pipeline) Gst.parseLaunch("udpsrc port=5000 ! jpegparse ! jpegdec ! queue ! appsink name=sink");
        AppSink sink = (AppSink) pipeline.getElementByName("sink");
        GstVideoComponent vc = new GstVideoComponent(sink);
        vc.setSize(1280, 720);
        vc.setVisible(true);
    
        frame = new JFrame();
        frame = new JFrame("Rover console");
        frame.add(vc);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setPreferredSize(new Dimension(1280, 720));
        frame.pack();
        pipeline.play();
        SwingUtilities.invokeLater(new Runnable() {
    
            @Override
            public void run() {
                frame.setVisible(true);
    
            }
        });
    }
}

I tried to :

• modify the code like the gstreamer-java example

• change udp by tcp

• use libcamera gstreamer plugin like

  gst-launch-1.0 libcamerasrc ! video/x-raw,colorimetry=bt709,format=NV12,width=1280,height=720,framerate=30/1 ! queue ! jpegenc ! multipartmux ! tcpserversink host=0.0.0.0 port=5000

but nothing change

public class GstreamerFrame {

    private static Pipeline pipeline;
    
    public static void main(String[] args) {
        Utils.configurePaths();
    
        Gst.init(Version.BASELINE, "BasicPipeline");
    
        EventQueue.invokeLater(() -> {
    
            GstVideoComponent vc = new GstVideoComponent();
            Bin bin = Gst.parseBinFromDescription("udpsrc port=5000 ! multipartdemux ! jpegdec", true);
            pipeline = new Pipeline();
            pipeline.addMany(bin, vc.getElement());
            Pipeline.linkMany(bin, vc.getElement());
    
            JFrame f = new JFrame("Camera Test");
            f.add(vc);
            vc.setPreferredSize(new Dimension(1280, 720));
            f.pack();
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
            f.setVisible(true);
            pipeline.play();
    
        });
    }

}

I'm not really an expert in gstreamer and video streams. Can somebody have an idea on what's going in there ?