Sorry but I am not a C++ developer so cannot provide a sample 

the following code provides a tick timer when the video or audio are playing.

        self.media_player.positionChanged.connect(self.pos_callback)

    def pos_callback(self, position) -> None:
        print(position)
        self.controller.media_play_item.timer = position

 This works fine until :        self.media_player.setLoops(QMediaPlayer.Loops.Infinite)

is used,

For the first time around it is fine but when the video loops the position value returns, the duration value, then a zero, then the duration, and then stops returning anything.