QVideoWidget doesn't display anything when used together with a QQuickWidget in a MainWindow

When we add any single QQuickWidget in Mainwindow and in parallel to that render Camera view using VideoSurface it stops displaying image in screen. Though we can save image in file system and it works fine.

For example Camera example project from installed example directory of Qt5.5. And add QQuickWidget in camera.ui. Add "QT+=quickwidgets" in project file. Now run application. It will just show you black screen instead of camera preview. Again rerun same application after reward back changes, it works fine.