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GStreamer-CRITICAL Error with QCamera

  • Dear All,

    I tried to run a simple project with QCamera and QMultimedia but my Camera isn't recognized correctly from GStreamer.

    This is my code:

    MainWindow::MainWindow(QWidget *parent)
        : QMainWindow(parent)
        , ui(new Ui::MainWindow)
        QCamera* camera;
        const QList<QCameraInfo> cameras = QCameraInfo::availableCameras();
        for (const QCameraInfo &cameraInfo : cameras)
            qDebug() << cameraInfo.deviceName();
            if (cameraInfo.deviceName() == "/dev/video0")
                camera = new QCamera(cameraInfo);
        qDebug() << camera;

    This is the output:

    Starting camera without viewfinder available
    (testCamera:4537): GStreamer-CRITICAL **: 12:43:01.419: gst_pad_get_current_caps: assertion 'GST_IS_PAD (pad)' failed
    (testCamera:4537): GLib-GObject-CRITICAL **: 12:43:01.419: g_object_set: assertion 'G_IS_OBJECT (object)' failed
    (testCamera:4537): GLib-GObject-CRITICAL **: 12:43:01.419: g_object_set: assertion 'G_IS_OBJECT (object)' failed
    CameraBin error: "GStreamer error: negotiation problem."
    Unable to query the parameter info: QCameraImageProcessingControl::WhiteBalancePreset : "Invalid argument"
    Unable to query the parameter info: QCameraImageProcessingControl::ColorTemperature : "Invalid argument"
    Unable to query the parameter info: QCameraImageProcessingControl::SharpeningAdjustment : "Invalid argument"
    CameraBin error: "Internal data stream error."

    And this is the caracteristics of camera

    Ubuntu 20.04 - Qt 5.12

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    Can you access that camera properly from GStreamer on the command line ?

  • No I've not find the right setting of GStreamer for my camera, the connection made Error after a few second.

     gst-launch-1.0 v4l2src ! jpegdec ! xvimagesink

    This i s the command I tried.

  • Lifetime Qt Champion

    Then are you sure your camera is working properly ?
    Which kernel version are you using ?
    Did you check if you have any message related to the camera in your logs ?

  • The camera works fine with Guvcview but not working on Cheese.

    My environment is Ubuntu 20.04 LTS on VirtualMachine, kernel version 5.8.0-55-generic

  • Lifetime Qt Champion

    Can you test the pipeline suggested in this stack overflow answer ?

  • Yes, I've already tested

    gst-launch-1.0 v4l2src device=/dev/video0 ! image/jpeg,width=640,height=480 ! decodebin ! ximagesink
    Setting pipeline to PAUSED ...
    Pipeline is live and does not need PREROLL ...
    Setting pipeline to PLAYING ...
    New clock: GstSystemClock
    ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Internal data stream error.
    Additional debug info:
    gstbasesrc.c(3072): gst_base_src_loop (): /GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
    streaming stopped, reason not-negotiated (-4)
    Execution ended after 0:00:00.417171499
    Setting pipeline to PAUSED ...
    Setting pipeline to READY ...
    Setting pipeline to NULL ...
    Freeing pipeline ...

  • Lifetime Qt Champion

    I wonder if it's a configuration issue. The default might be requesting something wrong.

    Can you for example force the image size to ensure it's something your camera supports ?

  • @SGaist

    in what way?
    This is the driver configuration

    2021-06-10 15_42_36-Window.png

  • Lifetime Qt Champion

    Sorry ! The code rendering made me miss that you configured the width/height of the image.

    One thing that looks wrong is the FPS that cannot be determined. I wonder if the issue lies there.

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