In a normal state, a video input interface receives video data. In a setup state, a control input interface receives multiple items of compressed image data, and stores the compressed image data in memory. In the normal state, a decoder reads one item from among the multiple items of compressed image data from the memory according to an instruction signal that indicates graphics data to be displayed, and decodes the compressed image data thus read so as to reproduce the original graphics data before compression. A multiplexer superimposes the graphics data on the video data.