Qt Video Frame opacity

[Sash0check]

Hello, i'm using samle vlc with pyqt5. I can't change opacity of any video. It changes frame opacity, but when i load video opacity disappears

self.opacity_effect = QGraphicsOpacityEffect()
self.opacity_effect.setOpacity(0.3)
self.videoframe.setGraphicsEffect(self.opacity_effect)

But if i change opacity of window then video is transparent.