In embedding an electronic watermark in a plurality of frames making up video data, the filtering processing is executed by omitting a portion of the frames in terms of time or space. The first mating part is complementary to the second mating part, so that they could be joined together to form a square or a rectangular frame. This allows a maximum pulse width, the size of switching elements, etc. The insert socket is further provided with an insulating body that carries the contact element and covers the connector opening in the connected state. In this structure, because the storage wires of a neighboring pixel are connected to each other through the storage wire connection line, the variation of the voltage for the storage capacitance may be minimized, and this results in a reduction of its distortion, such that crosstalk and flicker problems are minimized.