When I use this simple QML code:

    VideoOutput {
        anchors.fill: parent
        source: Camera {
            id: camera
            viewfinder {
                maximumFrameRate: 30
                minimumFrameRate: 30
            }
        }
    }

then I got a 'dynamic' artifacts when I move something in a camera view. But when an video is static, then I have not any artifacts. This artifacts are appeared only when something moves in a camera view (please, see a video from this URL: https://yadi.sk/i/JbPqVtoAME1F4Q ).

But, when I use the QtWidgets code (e.g. the Camera example from the QtMM), then I did not see any artifacts.

Following GStreamer pipeline does work too:

gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw,framerate=30/1' ! videoconvert ! autovideosink