This bug was originally titled "Video remains invisible when adding a Phonon widget into QGraphicView ". There are really two problems here:
1. Embedding Phonon::VideoWidget in QGraphicsView is currently not supported on Symbian
2. When the app is modified to use a QWidget-based UI, it fails for a different reason, namely the new title of this bug.
When adding a Phonon widget into QGraphicView or QGraphicScene, the z-order of the widgets' windows go wrong - audio is played correctly but no video can be seen. The effectiveWinId() of all visible objects in QGraphicView seem to be different in this case, therefore suspecting that this is a bug in the Symbian port.
When adding to QWidget, everything is fine.