Method and apparatus for processing a video signal so as to prohibit the making of acceptable videotape recordings

DETAILED DESCRIPTION It is an object of this invention to provide a method and apparatus for modifying a color video signal so that a conventional television receiver produces a normal color picture from the modified signal, whereas a videotape recording made from the modified signal is rendered unacceptable.
It is a more specific object of this invention to provide such a method and apparatus in which a pulse is inserted in the video signal following the trailing edge of the sync pulse during the blanking interval, whereby the added pulse causes an automatic level control circuit in a videotape recorder to erroneously sense video signal level and produce a gain correction that results in an unacceptable videotape recording.
Briefly, in accordance with one embodiment of the invention, a pulse is inserted in the video signal immediately following the trailing edge of the sync pulse.
This pulse which is inserted can be either a positive pulse or a negative pulse.
If the pulse is a positive pulse, an automatic level control circuit in a videotape recorder senses a sync pulse level greater than the actual value and produces a gain correction to reduce the recorded level of the video signal to an unacceptable level.
If the inserted pulse is a negative pulse, an automatic level control circuit in a videotape recorder senses a sync pulse level lower than its actual value, and produces a gain correction to increase the recorded level of the video signal to an unacceptable level.
Other objects and advantages of the present invention will appear from the detailed description taken in conjunction with the accompanying drawings.