Method for copy protection for video signal with added pulses

Abstract

Enhancements to a video anticopying process that causes an abnormally low amplitude video signal to be recorded on an illegal copy. In one version, positive going pulses are added to the video signal. 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. Also provided is apparatus for removing or attenuating these enhancements from the video signal, to allow copying.

1 - 8 . (canceled) 
   
   
       9 . A method to provide a copy protected video signal, comprising:
 adding pairs of positive going and negative going pulses to a vertical blanking interval of a video signal, the added pairs of pulses causing a reduced amplitude video signal on a recorded copy of the video signal;   providing a pulse generator which generates a waveform having an amplitude less than that of a horizontal synchronization pulse and insufficient to cause an erroneous synchronization or retrace: and   providing an adder which adds the generated waveform to at least part of a portion of the video signal thereby to cause in conjunction with the added pairs of pulses in a copy of the copy protected video signal an erroneous synchronization or retrace on at least one of a television set or a video cassette recorder, wherein the waveform enhances a copy protection effect of the added pairs of pulses.   
   
   
       10 . The method of  claim 9 , wherein the waveform defines a checker pattern. 
   
   
       11 . The method of  claim 9 , wherein the amplitude of the waveform is no more than about 20 IRE. 
   
   
       12 . A method to provide a copy protected video signal, comprising:
 adding pairs of positive going and negative going pulses to a vertical blanking interval of a video signal, the added pairs of pulses causing a reduced amplitude video signal on a recorded copy of the video signal;   providing a pulse generator which generates a waveform of a type for indicating a video retrace and having an amplitude less than that of a horizontal synchronization pulse and insufficient to cause an erroneous synchronization or retrace; and   providing an adder which substitutes the waveform in at least one horizontal line of the copy protected video signal at a location prior to a synchronization signal in place of an active video signal otherwise present at that location, wherein the location is in an overscan portion of the video signal and wherein the waveform enhances a copy protection effect of the pairs of pulses.   
   
   
       13 . The method of  claim 12 , wherein the waveform defines a checker pattern. 
   
   
       14 . The method of  claim 12 , wherein the amplitude of waveform is no more than about 20 IRE. 
   
   
       15 . A method to provide a copy protected video signal, comprising:
 adding pairs of positive going and negative going pulses to a vertical blanking interval of a video signal, the added pairs of pulses causing a reduced amplitude video signal on a recorded copy of the video signal;   providing a pulse generator which generates a waveform of a type for indicating a video retrace and having an amplitude less than that of a horizontal synchronization pulse and insufficient to cause an erroneous synchronization or retrace; and   providing an adder which substitutes the waveform in at least one horizontal line of the copy protected video signal at a location following a synchronization signal of the video signal, wherein the waveform increases picture degradation of the copied signal.   
   
   
       16 . The method of  claim 15 , wherein the waveform defines a checker pattern. 
   
   
       17 . The method of  claim 15 , wherein the amplitude of the waveform is no more than about 20 IRE. 
   
   
       18 . A method to provide a copy protected video signal, comprising:
 adding pairs of positive going and negative going pulses to a vertical blanking interval of a video signal, the added pairs of pulses causing a reduced amplitude video signal on a recorded copy of the video signal;   providing a pulse generator which generates a waveform of a type for causing a television set on which the copy is being viewed to retrace horizontally prior to occurrence of a horizontal sync signal and having an amplitude less than that of a horizontal synchronization pulse and insufficient to cause an erroneous synchronization or retrace; and   providing an adder which substitutes the waveform in at least one horizontal line of the copy protected video signal at a location prior to the horizontal sync signal in that line in place of an active video signal otherwise present at that location, wherein the waveform increases picture degradation of the copied signal.   
   
   
       19 . The method of  claim 18 , wherein the waveform defines a checker pattern. 
   
   
       20 . The method of  claim 18 , wherein the amplitude of the waveform is no more than about 20 IRE. 
   
   
       21 . A method of providing a video copy protection signal with a high frequency level shifting signal, comprising:
 providing a basic copy protection signal to a video signal by inserting or adding one or more positive going pulses to cause gain reduction in an AGC amplifier of a video recorder;   providing a generator which generates a high frequency signal in the range of 100 KHz to 5 MHz; and   providing an adder which adds the high frequency signal in an overscan portion of the video signal, whereby the high frequency signal causes a level shifting effect on a portion of the basic video copy protection signal.   
   
   
       22 . A method of providing a copy protected video signal, comprising:
 adding one or more pairs of positive going and negative going pulses to a vertical blanking interval following a line synchronization pulse in the video signal;   providing a pulse generator which generates a series of pulses; and   providing an adder which adds the series of pulses to an overscan or blanking interval of the video signal, wherein the added series of pulses each have a maximum amplitude less than an amplitude of sync tip level of the line synchronization pulses and insufficient to cause an erroneous synchronization or retrace, and wherein the added series of pulses enhance a copy protection effect of the added pairs of pulses.   
   
   
       23 . The method of  claim 22 , wherein the added series of pulses define a checker pattern. 
   
   
       24 . The method of  claim 22 , wherein the amplitude of the added pulses is no more than about 20 IRE. 
   
   
       25 . A method for providing a video copy protection signal with a high frequency level shifting signal, comprising:
 receiving a video signal from a source of a video signal;   providing a generator which generates a high frequency signal in the range of 100 KHz to 5 MHz;   providing an adder which adds the high frequency signal to an overscan portion of the video signal, whereby the high frequency signal causes a level shifting effect in a portion of a basic copy protection signal in the received video signal, wherein the basic copy protection signal includes one or more positive going pulses to cause gain reduction in an AGC amplifier of a video recorder; and   outputting the video signal with the level shifting effect.