The display information generating unit manages a first plane that contains video information and a second plane that contains first still information and second still information, and merges the first plane and second plane. The control unit adds at least one of the first still information and second still information to the second plane when an interrupt signal is generated. If the display area of the video information is the full display area of the display screen, the control unit starts a screen saver operation that changes the first still information after a first predetermined period from a time point of the interrupt signal. If the display area of the video information is smaller than the full display area of the display screen, the control unit starts a screen saver operation that changes the second still information after a second predetermined period from a time point of the interrupt signal.