Enhancements to a video anticopying process that causes an abnormally low
amplitude video signal to be recorded on an illegal copy. The
enhancements in one version introduce into the overscan portion of the
television picture, just prior to the horizontal or vertical sync signals
but in active video, a negative going waveform that appears to the
television receiver or videotape recorder to be a sync signal, thereby
causing an early horizontal or vertical retrace. One version provides (in
the right overscan portion of the picture), a checker pattern of
alternating gray and black areas which causes the TV set on which the
illegal copy is played to horizontally retrace earlier than normal in
selected lines with a consequential horizontal shift of the picture
information on those lines. This substantially degrades picture
viewability. In another version a gray pattern at the bottom overscan
portion of the picture causes vertical picture instability. In another
version selected horizontal sync signals are narrowed, causing irregular
vertical retraces. In another version, a negative-going pulse is added to
the back porch region of the horizontal blanking interval. Also provided
is apparatus for removing or attenuating these enhancements from the
video signal, to allow copying.