METHOD OF AND APPARATUS FOR CLEARING AWAY THE MODIFICATION INCREASING DEGREE OF PROTECTING A VIDEO SIGNAL AGAINST COPYING

摘要

The method involves blanking a portion of a video signal at a location in the over-scan portion of the video signal prior to a synchronisation signal. A waveform for indicating a video retrace prior to occurrence of the synchronisation signal is added to the blanked location. The adding step involves adding the waveform only to portions of the video signal having active video prior to the blanking step.