PURPOSE: To extract the area and boundary of a picture in a constitution enabling an actual time processing by dividing a signal waveform into envelope amplitude and carrier phase information, and analyzing it in a time area.

CONSTITUTION: The envelope amplitude of a picture signal is extracted by an Hilbert converter 1, and the carrier phase information of the picture signal is extracted by a phase synchronizing group. The changing points of the envelope components and the carrier components are detected by a detector 4, and a time of point indicating the changing point larger than a certain set value is outputted as a picture area boundary. Therefore, an optimal area judgement can be attained, a one-dimensional signal processing is obtained, and a circuit constitution is simple, so that the actual time processing can be attained, this system can be applied for a TV picture signal or the like, and a picture quality can be improved.