[Problem] To make a device compact and inexpensive by omitting a frame buffer.[Solution] First packet data PD1 that is sequentially received from a first camera C1 and second packet data PD2 that is sequentially received from a second camera C2 are alternately and sequentially transmitted to an external device 2 before data for one screen is accumulated. Therefore, a frame buffer for saving the data for one screen is not necessary, and a device can be made correspondingly more compact and less expensive.