According to one embodiment, a low-pass filter operation circuit constitutes a serial interface, which enables communication conforming to the serial bus standard including IEEE 1394 & USB 3.0, together with a timer register, a packet receiving circuit, and a packet transmitting circuit. The low-pass filter operation circuit performs a correction of gradually increasing or decreasing an internal timer value counted by the timer register by a unit count value thereof, thereby converging the deviation. A timer operation circuit calculates a timer reference value, corresponding to the timing at which sync. should be done next, common to cameras, based on a timer value in the timer register, and a frame rate generated by CPU.