A video input interface receives input video data in a normal state. A control input interface receives character data for On Screen Display (OSD) in a setup state. An encoder encodes the character data and stores encoded compressed data in a memory in the setup state. A decoder receives an instruction signal designating the character data to be displayed, reads, and decodes one piece of compressed data corresponding to the instruction signal from the memory, and reproduces the original character data in the normal state. A multiplexer superimposes character data on frame data and outputs the data.