Method and apparatus for disabling anti-copy protection system in video signals

Abstract

A method and apparatus for disabling the effect of copy-protect signals placed in a recording video signals which is based on differences in the characteristics of television and VCR circuitry. Copy-protect signals include pseudo-sync pulses and/or added AGC pulses in the blanking interval of a video signal. The specific method described includes altering the level of the video signal during the vertical blanking interval, e.g., level-shifting, so as to render the copy-protect copy protection signals ineffective to prevent in preventing unauthorized copying by a VCR. A circuit for achieving the method includes a sync separator for detecting the vertical blanking interval, pulse generating circuits for producing pulses of predetermined widths during this interval, and a summing circuit for summing the predetermined pulses with copy-protect signals thereby to shift their level. An alternative method includes increasing the effective frequency of the copy-protect signals during the vertical blanking interval so as to achieve attenuation and/or low-pass filtering in the VCR circuitry to there by render rendering the modified signals ineffective in preventing copying. A circuit for achieving this method includes pulse narrowing and/or pulse multiplication circuitry which effectively increased the high-frequency content of the pseudo-sync and/or AGC pulses.

1. A method for disabling the effects of copy-protect signals added to blanking intervals of a video signal having normal sync pulses, said copy-protect signals including at least one added AGC pulse, said method comprising the steps of:
 providing the video signal having said copy-protect signals added thereto;  
 detecting said blank interval of said video signal;  
 identifying the position of said at least one added AGC pulse; and  
 developing altered video signals in response to said detecting and identifying steps in a manner so as to alter the copy-protect signals to reduce their effectiveness in copy-prevention;  
 wherein said developing step comprises generating a pulse of a predetermined width during said blanking interval and combining said generated pulse with copy-protect signals thereat so as to shift a DC level of at least a part of the copy-protect signals in a manner to disable copy protection.  
 
     
     
       2. A method as recited in  claim 1  wherein said copy-protect signals inhibit copying by a video cassette recorder and wherein said developing step comprises altering, reproducing or regenerating said copy-protect signals in a manner where internal characteristics of said video cassette recorder inherently nullify the effects of said copy-protect signals. 
     
     
       3. A method as recited in  claim 2  wherein said developing step comprises attenuating said copy-protect signals beyond a range of signal sensitivity of said video cassette recorder without eliminating said copy- protect signals.    
     
     
       4. A method for disabling the effects of copy-protect signals added to blanking intervals of a video signal having normal sync pulses, said copy-protect signals including at least one added AGC pulse, said method comprising the steps of:
 detecting said blanking interval of said video signal;  
 identifying the position of said at least one added AGC pulse; and  
 developing altered video signals in response to said detecting and identifying steps in a manner so as to alter the copy-protect signals to reduce their effectiveness in copy-prevention;  
 wherein said copy-protect signals inhibit copying by a video cassette recorder and wherein said developing step comprises altering, reproducing or regenerating said copy-protect signals in a manner where internal characteristics of said video cassette recorder inherently nullify the effects of said copy-protect signals; and  
 wherein said developing step comprises increasing a frequency of said copy-protect signals beyond an effective bandwidth of a video cassette recorder.  
 
     
     
       5. A method as recited in  claim 4  wherein said developing step comprises increasing an effective frequency of said copy-protect signals by narrowing widths of the pulses of said copy-protect signals. 
     
     
       6. A method as recited in  claim 4  wherein said developing step comprises increasing an effective frequency by effectively time-compressing said copy-protect signals. 
     
     
       7. A method as recited in any of the previous  preceding claims wherein said blanking interval is a vertical blanking interval following a normal viewing field. 
     
     
       8. A method as recited in claims  1  through  6   any of claims  1 -   6   wherein said video signal is a prerecorded video signal on a video cassette videotape. 
     
     
       9. A method for reducing the effect of copy-protect signals in a blanking interval of a video signal wherein said copy-protect signals include at least one added AGC pulse, and said blanking interval includes at least one normal sync pulse, said method comprising the steps of:
 receiving an input video signal from said recording medium;  
 detecting the normal sync signal and identifying the location of said copy-protect signals on the basis of the detected normal sync signal;  
 generating copy-protect disabling signals which increase a frequency of said copy-protect signals beyond an effective bandwidth of a video cassette recorder in accordance with said detecting step; and  
 transmitting an output video signal comprising a composite of said input video signal and said disabling signals.  
 
     
     
       10. A method for reducing the effect of copy-protect signals in a vertical blanking interval of a video signal wherein said copy-protect signals include at least one pseudo-sync pulse and an added AGC pulse, and said blanking interval includes at least one normal vertical sync pulse, said method comprising the steps of:
 receiving an input video signal from said recording medium;  
 detecting the vertical sync signal and identifying the location of said copy-protect signals on the basis of the detected vertical sync signal;  
 generating copy-protect disabling signals which increase a frequency of said copy-protect signals beyond an effective bandwidth of a video cassette recorder in accordance with said detecting step; and  
 transmitting an output video signal in accordance with a representation of said input video signal and said disabling signals.  
 
     
     
       11. An apparatus for disabling the effects of copy-protect signals in a video signal, said copy-protect signals including at least one added AGC pulse, said apparatus comprising:
 receiving means for receiving an input signal representative of said video signal;  
 detection means connected with said receiving means for detecting said copy-protect signals;  
 signal disabling means responsive to said detection means for generating disabling signals; and  
 output means for transmitting an output video signal in accordance with a representation of said input video signal and said disabling signals;  
 wherein said signal disabling means includes level-shifting means for effecting transmission of an output video signal at least a portion of which having its D.C. level shifted.  
 
     
     
       12. An apparatus as recited in  claim 11  wherein said disabling means includes means for attenuating said copy-protect signals without eliminating said copy- protect signals.    
     
     
       13. An apparatus for disabling the effects of copy-protect signals in a video signal, said copy-protect signals including at least one added AGC pulse, said apparatus comprising:
 receiving means for receiving an input signal representative of said video signal;  
 detection means connected with said receiving means for detecting said copy-protect signals;  
 signal disabling means responsive to said detection means for generating disabling signals; and  
 output means for transmitting an output video signal in accordance with a representation of said input video signal and said disabling signals;  
 wherein said disabling means includes means for increasing an effective frequency of said copy-protect signals.  
 
     
     
       14. An apparatus as recited in any of the previous  claims 11  to  13  wherein said video signal is a prerecorded video signal from a videotape. 
     
     
       15. An apparatus for disabling the effects of copy-protect signals contained in vertical blanking intervals of a video signal, said copy-protect signals including at least one added pseudo-sync signal and one added AGC pulse, said apparatus comprising:
 receiving means for receiving an input signal representative of said video signal from said recording medium;  
 detection means connected with said receiving means for detecting said vertical blanking interval which includes said copy-protect signals;  
 signal disabling means responsive to said detection means for generating disabling signals during the occurrence of at least a portion of said copy-protect signals; and  
 output means for transmitting an output video signal in accordance with a representation of said input video signal and said disabling signals;  
 wherein said detection means comprises a sync separator for detecting the vertical blanking interval of the video signal, said disabling means comprises means for generating a D.C. level-shifting signal during a portion of the vertical blanking interval, and said output means includes means for combining the D.C. level-shifting signal with a representation of the input video signal, thereby to transmit an output video signal having disabled copy-protect signals.  
 
     
     
       16. An apparatus as recited in  claim 15  wherein said detection means comprises a sync separator for separating the vertical blanking interval from the remaining video signal, said disabling means comprises means for attenuating without eliminating said copy- protect signals  at least a portion of said copy-protect signals thereby to produce attenuated copy-protect signals, and said output means includes means for transmitting the attenuated copy-protect signals and a representation of the input video signal thereby to transmit an output video signal having disabled copy-protect signals. 
     
     
       17. An apparatus for disabling the effects of copy-protect signals contained in vertical blanking intervals of a video signal, said copy-protect signals including at least one added pseudo-sync signal and one added AGC pulse, said apparatus comprising:
 receiving means for receiving an input signal representative of said video signal from said recording medium;  
 detection means connected with said receiving means for detecting said vertical blanking interval which includes said copy-protect signals;  
 signal disabling means responsive to said detection means for generating disabling signals during the occurrence of at least a portion of said copy-protect signals; and  
 output means for transmitting an output video signal in accordance with a representation of said input video signal and said disabling signals;  
 wherein said detection means comprises a sync separator for separating the vertical blanking interval from the remaining video signal, said disabling means comprises means for increasing an effective frequency of said copy-protect signals thereby to produce altered signals, and said output means includes means for transmitting the altered signals and a representation of the input video signal.  
 
     
     
       18. A method for reducing effects of copy- protect signals in vertical blanking intervals of a video signal, said copy - protect signals including pulses added to said vertical blanking intervals, said method comprising the steps of:      receiving a video signal having said pulses added thereto;        detecting a vertical blanking interval of said video signal;        shifting a voltage level of at least a part of said video signal in said vertical blanking interval, wherein the only negative - going pulses present in said vertical blanking interval extending below a voltage reference level are horizontal sync pulses, thereby enabling copying of said video signal.     
     
     
       19. The method of  claim 18  wherein said voltage reference level is that of processing circuitry of a video cassette recorder. 
     
     
       20. The method of  claim 19  wherein said voltage reference level is an AGC level. 
     
     
       21. The method of  claim 18  wherein said video signal is a prerecorded video signal on a video cassette tape. 
     
     
       22. A method for reducing effects of copy- protect signals in blanking intervals of a video signal, said copy - protect signals including at least one added pulse and each blanking interval including at least one sync pulse preceding said added pulse, said method comprising the steps of:      receiving an input video signal;        detecting said at least one sync pulse;        generating copy - protect disabling signals which increase a frequency of said copy - protect signals beyond an effective bandwidth of a video cassette recorder, in accordance with said detecting step; and        providing an output video signal including a composite of said input video signal and said disabling signals.     
     
     
       23. A method as recited in  claim 22  wherein said generating step comprises increasing an effective frequency of said copy- protect signals by narrowing widths of the pulses of said copy - protect signals.   
     
     
       24. A method as recited in  claim 22  wherein said generating step comprises increasing an effective frequency by effectively time- compressing said copy - protect signals.   
     
     
       25. A method as recited in  claim 22  wherein said blanking interval is a vertical blanking interval following a normal viewing field. 
     
     
       26. A method as recited in  claim 22  wherein said video signal is a prerecorded video signal on a video cassette tape. 
     
     
       27. An apparatus for reducing effects of copy- protect signals in a video signal, said copy - protect signals including at least one added pulse, said apparatus comprising:      a video input terminal receiving an input signal representative of said video signal;        a sync separator having an input terminal connected to said video input terminal and having an output terminal, thereby providing at said output terminal a signal indicating a blanking interval of said video signal;        disabling circuitry having an input terminal connected to said output terminal of said sync separator, and having an output terminal, providing at said output terminal of said disabling circuitry altered copy - protect signals having an increased effective frequency; and        a video output terminal connected to said output terminal of said disabling circuitry and to said video input terminal, thereby providing a composite of said input video signal and said altered copy - protect signals.     
     
     
       28. An apparatus as recited in  claim 27  wherein said disabling circuitry increases an effective frequency of said copy- protect signals by narrowing widths of the pulses of said copy - protect signals.   
     
     
       29. An apparatus as recited in  claim 27  wherein said disabling circuitry increases an effective frequency by effectively time- compressing said copy - protect signals.   
     
     
       30. An apparatus as recited in  claim 27  wherein said blanking interval is a vertical blanking interval following a normal viewing field. 
     
     
       31. An apparatus as recited in  claim 27  wherein said video signal is a prerecorded video signal on a video cassette tape. 
     
     
       32. A method for reducing effects of copy- protect signals in vertical blanking intervals of a video signal, said copy - protect signals including pulses added to said vertical blanking intervals, said method comprising the steps of:      receiving a video signal having said pulses added thereto;        detecting a vertical blanking interval of said video signal;        shifting a voltage level of at least a part of said video signal in said vertical blanking interval, wherein the only negative - going pulses present in said vertical blanking interval extending below a voltage reference level are horizontal sync pulses or vertical sync pulses, thereby enabling copying of said video signal.     
     
     
       33. A method as recited in  claim 32 , wherein said copy- protect signals include pseudo - sync pulses that are shifted to a voltage level above the level of the horizontal sync tip voltage or the pseudo - sync pulses are shifted to a level above the slice threshold for sync separation.   
     
     
       34. A method as recited in  claim 32 , wherein all or part of said copy- protect signals are shifted in voltage to render the resulting copy - protect signals ineffective to prevent copying by a video cassette recorder.   
     
     
       35. A method for reducing the effects of copy- protect signals in vertical blanking intervals of a video signal, said copy - protect signals including pulses added to said vertical blanking intervals, said method comprising:      receiving a video signal having said pulses added thereto;        detecting a vertical blanking interval of said video signal; and        regenerating at least a part of said video signal in said vertical blanking interval, wherein the only negative - going pulses present in said vertical blanking interval extending below a voltage reference level and detectable by a video cassette recorder sync separator are horizontal or vertical sync pulses, thereby enabling copying of said video signal.     
     
     
       36. A method as recited in  claim 35 , wherein said regenerating comprises regenerating at least a part of said video signal in said vertical blanking interval without AGC pulses. 
     
     
       37. A method as recited in  claim 35 , wherein said voltage reference level is that of processing circuitry of a video cassette recorder. 
     
     
       38. A method as recited in  claim 35 , wherein said voltage reference level is an AGC level. 
     
     
       39. A method for reducing the effects of copy- protect signals in vertical blanking intervals of a video signal, said copy - protect signals including pulses added to said vertical blanking intervals, said method comprising:      receiving a video signal having said pulses added thereto;        detecting a vertical blanking interval of said video signal; and        regenerating at least a part of said video signal in said vertical blanking interval, wherein the only negative - going pulses present in said vertical blanking interval extending below a voltage reference level and detectable by a video cassette recorder sync separator are normal sync pulses, thereby enabling copying of said video signal.     
     
     
       40. A method as recited in  claim 39 , wherein said regenerating comprises regenerating at least a part of said video signal in said vertical blanking interval without added AGC pulses. 
     
     
       41. A method as recited in  claim 39 , wherein said voltage reference level is that of processing circuitry of a video cassette recorder.