Problem resizing QGraphicsVideoItem / QGraphicsScene

[AlterX]

Hi there...
I'm creating my own app to play different videos in parallel. I've started using Qt example "videographicsitem" and so my code looks like this:
@
videoItem = new QGraphicsVideoItem;

QGraphicsScene *scene = new QGraphicsScene(this);
QGraphicsView *graphicsView = new QGraphicsView(scene);
scene->addItem(videoItem);

QBoxLayout *layout = new QVBoxLayout;
layout->addWidget(graphicsView);
setLayout(layout);
mediaPlayer.setVideoOutput(videoItem);

@

Ok, so I have to resize my graphicsview using mouse preserving aspectrazio and this works very well using this code:
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QGraphicsView *view = NULL;

view = this->findChild<QGraphicsView*>("graphView");
view->fitInView(videoItem, Qt::KeepAspectRatio);

@
in the resizeEvent of VideoPlayer's parent.
My problem is that code above doesn't do nothing if I just put VideoPlayer widget (using setGeometry); video inside is not fit and I have to resize with mouse to get video fitted.

Someone knows how I can properly fit video just setting dimension with setGeometry()?

thanks in advance
Gianni