Performance issue of QQuickPaintedItem

I am developing a custom QML extension by QQuickPaintedItem. The document said you have to call the update() function when the appearance is changed, so I call it every 33ms (I am making a video player component, but it also said the update() function “will trigger a repaint of the whole scene.”
So, if I create multiple video player components in the QML, it will cause lots of repainting, and it make the performance worse. Any suggesstion for me? thanks!