Additional information superimposition device

摘要

Additional information is superimposed consistently while the disturbance of a picture due to excessive superimposition is suppressed. The device superimposes a spectrally spread additional information on a video signal. Inverse spread processing is performed on the video signal, and an SS additional information detection circuit detects whether additional information is superimposed already on the video signal. Based on the detection result performed by the additional information detection circuit, superimposition of the spectrally spread signal supplied from the spectrally spread signal generator on the video signal is controlled. A superimposition control method such as superimposition ON/OFF control, superimposition level control, or spread code string control is performed.