| 摘要 |
PROBLEM TO BE SOLVED: To surely detect a copy prohibition signal by a pseudo-horizontal synchronizing signal from an inputted video signal. SOLUTION: A composite synchronizing signal of a video signal to which synchronizing tip clamp is performed is separated by a synchronizing signal separating circuit 102, vertical and horizontal synchronizing signals of the video signal are simultaneously detected by vertical and horizontal synchronizing signal detecting circuits 103, 104. A pulse is generated in a horizontal synchronizing period in a vertical blanking period based on these synchronizing signals by a timing generating circuit 106. The composite synchronizing signal is integrated for a period of the pulse by an integration circuit 107. Since this integrated output becomes larger when the pseudo-horizontal synchronizing signal exists in the period of the pulse than when no pseudo-horizontal synchronizing signal exists in the period of the pulse, presence/absense of the pseudo-horizontal synchronizing signal is judged based on the integrated output by a judging circuit 108. |
