I've been googling for days now and haven't found a solution yet...

I am streaming a video with gstreamer into a QGraphicsView and everything is working perfectly, but now i want to have some elements which lay over the video for example QLabels and QButtons. They do have transparent corners and everything when laying upon each other but as soon as they're over the video, they turn black (see picture below).
!http://i.imgur.com/WOAajWM.png(http://i.imgur.com/WOAajWM.png)!

I've tried things as
->setStyleSheet("*{background-color: transparent}");
->setAttribute(Qt::WA_TranslucentBackground);
->setAtrtibute(Qt::WA_NoSystemBackground);
but I'm still getting these ugly black boxes :/ Apparently there're some issues with widgets laying over video...

I'd appreciate any possible help!
Thanks,
Frede