Anti-copying video signal processing

• US 5,034,981 A
• Filed: 12/27/1989
• Issued: 07/23/1991
• Est. Priority Date: 04/11/1988
• Status: Expired due to Fees

• Current Assignee: Leghorn Telepublishing Corporation
• Original Assignee: Eidak Corporation
• Inventors: Perlman, Bill, Dolson, William R., Leonard, Eugene, Budai, Karoly
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US07/457,928
• Time in Patent Office: 573 Days
• Field of Search: 380/5, 380/14, 380/15, 360/60
• US Class Current: 380/204
• CPC Class Codes: G11B 27/028 with computer assistance
• CPC Class Codes: H04N 2005/91378 the video line number being modulated
• CPC Class Codes: H04N 2005/91385 the video frame number being modulated
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• CPC Class Codes: H04N 7/169 Systems operating in the time domain of the television signal
• CPC Class Codes: H04N 9/79 Processing of colour television signals in connection with recording

Abstract

Counting circuitry in the vertical synchronizing circuit of a video receiver is prevented from generating vertical control signals at a fixed, standard periodicity when the video signal transmitted to that receiver exhibits a changing field interval which varies above and below that standard period. At least one of the vertical pulses in the vertical period of each field interval as well as plural equalizing pulses in the post equalizing period in that field interval are deleted from the video signal. To minimize perturbations in the video picture displayed from that video signal, the time of occurrence of the first vertical pulse in selected field intervals is shifted.

Claims

1. A method of preventing counting circuitry included in the vertical synchronizing circuit of a video receiver from generating vertical control signals at a fixed, standard rate when a video signal transmitted to said video receiver exhibits a changing field interval which varies above and below a fixed, standard period, said method comprising the steps of deleting at least one of the vertical pulses in the vertical period of each field interval of said transmitted video signal;

and deleting plural equalizing pulses in the post equalizing period following said vertical pulses in said field interval.

2. The method of claim 1 wherein the step of deleting at least one of the vertical pulses in the vertical period comprises deleting a vertical pulse that commences at substantially the midpoint of a line interval included in said vertical period.

3. The method of claim 2 wherein the deleted vertical pulse is the last vertical pulse that commences at substantially the midpoint of a line interval.

4. The method of claim 3 wherein the deleted vertical pulse is the last vertical pulse in each FIELD I interval and is the penultimate vertical pulse in each FIELD II interval.

5. The method of claim 1 wherein the step of deleting plural equalizing pulses comprises deleting a selected number of those equalizing pulses in the post equalizing period following said vertical pulses and commencing at substantially the midpoint of a line interval in said post equalizing period.

6. The method of claim 5 wherein the selected number of equalizing pulses that are deleted comprises all of the equalizing pulses that commence at substantially the midpoints of line intervals in said post equalizing period.

7. The method of claim 1 further comprising the step of identifying the last line interval in the changing vertical period of the transmitted video signal, and detecting the vertical period in the next-following field interval of said transmitted video signal, whereby the vertical and equalizing pulses to be deleted are determined.

8. The method of claim 7 wherein the step of determining the vertical and equalizing pulses to be deleted comprises counting line intervals in said next-following field interval, and deleting selected vertical and equalizing pulses in predetermined line intervals.

9. The method of claim 1 further comprising the step of shifting the time of occurrence of the first vertical pulse in the vertical period of selected field intervals.

10. The method of claim 9 wherein the step of shifting the time of occurrence of the first vertical pulse comprises advancing the time of occurrence of said first vertical pulse when the field interval of the transmitted video signal is increased and delaying the time of occurrence of said first vertical pulse when the field interval of the transmitted video signal is decreased.

11. The method of claim 9 wherein the shift of the time of occurrence of the first vertical pulse is on the order of about one-third of a horizontal line interval.

12. A method of controlling vertical and equalizing pulses in the vertical synchronizing interval of a video signal transmitted with a changing frame period which varies above and below a fixed standard period to enable a video picture to be displayed therefrom on a conventional television receiver but prevent that video signal from being copied on a conventional video recorder, said method comprising the steps of generating less than a standard number of vertical pulses in each vertical period of the vertical synchronizing interval;

selectively shifting the beginning of selected vertical periods;

generating less than a standard number of post equalizing pulses in each vertical synchronizing interval; and

combining the video signal with the generated vertical and post equalizing pulses, whereby a vertical synchronizing circuit of a television receiver is inhibited from locking onto the vertical synchronizing interval of said video signal and thereby generate vertical control signals at said fixed, standard period, and whereby perturbations in the displayed video picture attributed to a change in the frame period of the video signal are minimized.

13. The method of claim 12 wherein the step of generating less than a standard number of vertical pulses comprises generating a series of vertical pulses, and inhibiting at least one of the vertical pulses in said series.

14. The method of claim 13 wherein the vertical pulses in said series are generated at the beginning and at the midpoint of predetermined line intervals, and said step of inhibiting comprises inhibiting the last midpoint-generated vertical pulse in said series.

15. The method of claim 12 wherein the step of generating less than a standard number of post equalizing pulses comprises generating a series of post equalizing pulses, and inhibiting selected post equalizing pulses in said series.

16. The method of claim 15 wherein the post equalizing pulses in said series are generated at the beginning and at the midpoint of predetermined line intervals, and said step of inhibiting comprises inhibiting the midpoint-generated post equalizing pulses in said series.

17. The method of claim 12 wherein the step of selectively shifting the beginning of selected vertical periods comprises shifting the time of occurrence of the first vertical pulse in selected vertical periods.

18. The method of claim 17 wherein said selected vertical periods comprise the vertical periods in FIELD II intervals of the video signal.

19. The method of claim 17 wherein the time of occurrence of the first vertical pulse is shifted by no more than half a line interval.

20. The method of claim 17 wherein the step of shifting the time of occurrence of the first vertical pulse comprises advancing said time of occurrence when the frame period of the video signal increases and delaying said time of occurrence when the frame period of said video signal decreases.

21. The method of claim 20 wherein said first vertical pulse is produced by generating a start vertical pulse at a predetermined location in said vertical synchronizing interval, commencing the count of clock pulses in response to said start vertical pulse, and generating a vertical pulse commencing with said start vertical pulse and ending when said count reaches a predetermined count.

22. The method of claim 21 wherein said first vertical pulse is advanced by advancing the location in the vertical synchronizing interval at which said start vertical pulse is generated, and said first vertical pulse is delayed by delaying the location in the vertical synchronizing interval at which said start vertical pulse is generated.

23. The method of claim 22 wherein s id steps of advancing and delaying the location in the vertical synchronizing interval at which said start vertical pulse is generated comprises generating advanced and delayed start pulses at respective, predetermined locations in said vertical synchronizing interval and selecting said advanced or delayed start pulse from which the start vertical pulse commences.

24. A method of generating pre-equalizing, post-equalizing and vertical pulses for insertion into the vertical synchronizing interval of a transmitted video signal, comprising the steps of counting horizontal line intervals in each field of the video signal;

generating start equalizing representations representing the start of respective pre-equalizing and post-equalizing pulses at predetermined line counts and omitting selected ones of the start equalizing representations at preselected line counts;

generating start vertical representations representing the start of respective vertical pulses at other predetermined line counts and omitting selected ones of the start vertical representations at preselected ones of said other line counts;

counting clock signals in response to each start equalizing representation and each start vertical representation to produce clock counts;

sensing when the clock count reaches a first count following a start equalizing representation and a second count following a start vertical representation;

generating equalizing pulses of durations determined by said first count; and

generating vertical pulses of durations determined by said second count, whereby equalizing and vertical pulses are not generated when start equalizing and start vertical representations are omitted.

25. The method of claim 24 wherein the step of generating start equalizing representations comprises generating a start equalizing representation at the beginning and at the midpoint of those horizontal line intervals corresponding to said predetermined line counts;

and the step of omitting selected start equalizing representations comprises omitting the start equalizing representations at the midpoint of the line intervals corresponding to at least some post-equalizing line counts.

26. The method of claim 24 wherein the step of generating start vertical representations comprises generating a start vertical representation at the beginning and at the midpoint of those horizontal line intervals corresponding to said other predetermined line counts;

and the step of omitting selected start vertical representations comprises omitting the start vertical representation at the midpoint of the line interval corresponding to at least one of said other predetermined counts.

27. The method of claim 26 wherein the video signal exhibits a changing frame period which varies above and below a fixed standard period, and wherein the step of generating a start vertical representation at the beginning and at the midpoint of horizontal line intervals further comprises advancing the location of the first start vertical representation when the frame period increases and delaying the location of the first start vertical representation when the frame period decreases.

28. The method of claim 27 wherein the first star vertical representation is respectively advanced or delayed on the order of about one-third the duration of a horizontal line interval.

29. The method of claim 28 further comprising the steps of sensing when the clock count reaches a third count following an advanced first start vertical representation;

sensing when the clock count reaches a fourth count following a delayed first start vertical representation; and

generating a first vertical pulse of duration determined by the third or fourth count.

30. Apparatus for preventing counting circuitry included in the vertical synchronizing circuit of a video receiver from generating vertical control signals at a fixed, standard rate when a video signal transmitted to said video receiver exhibits a changing field interval which varies above and below a fixed, standard period, said apparatus comprising synchronizing signal generating means for controlling the synchronizing signals included in the transmitted video signal, including vertical pulse control means for deleting at least one of the vertical pulses in the vertical period of each field interval of said transmitted video signal;

and equalizing pulse control means for deleting plural equalizing pulses in the post equalizing period following said vertical pulses in said field interval.

31. The apparatus of claim 30 wherein said vertical pulse control means comprises means for deleting a vertical pulse that commences at substantially the midpoint of a line interval included in said vertical period.

32. The apparatus of claim 31 wherein said means for deleting deletes the last vertical pulse that commences at substantially the midpoint of a line interval.

33. The apparatus of claim 32 wherein the deleted vertical pulse is the last vertical pulse in each FIELD I interval and is the penultimate vertical pulse in each FIELD II interval.

34. The apparatus of claim 30 wherein said equalizing pulse control means comprises means for deleting a selected number of those equalizing pulses in the post equalizing period following said vertical pulses and commencing at substantially the midpoint of a line interval in said post equalizing period.

35. The apparatus of claim 34 wherein the last-mentioned means for deleting deletes all of the equalizing pulses that commence at substantially the midpoints of line intervals in said post equalizing period.

36. The apparatus of claim 30 wherein the synchronizing signal generating means further includes line identifying means for identifying the last line interval in the changing vertical period of the transmitted video signal, and means responsive to said last line interval for detecting the vertical period in the next-following field interval of said transmitted video signal to determine the vertical and equalizing pulses to be deleted.

37. The apparatus of claim 36 wherein the means to determine the vertical and equalizing pulses to be deleted comprises line counting means for counting line intervals in said next-following field interval, and means for deleting selected vertical and equalizing pulses at predetermined line counts.

38. The apparatus of claim 30 wherein the synchronizing signal generating means further includes shift means for shifting the time of occurrence of the first vertical pulse in the vertical period of selected field intervals.

39. The apparatus of claim 38 wherein the shift means comprises advance means for advancing the time of occurrence of said first vertical pulse when the field interval of the transmitted video signal is increased and delay means for delaying the time of occurrence of said first vertical pulse when the field interval of the transmitted video signal is decreased.

40. The apparatus of claim 38 wherein the shift of the time of occurrence of the first vertical pulse is on the order of about one-third of a horizontal line interval.

41. Apparatus for generating vertical and equalizing pulses inserted into the vertical synchronizing interval of a video signal transmitted with a changing frame period which varies above and below a fixed standard period to enable a video picture to be displayed therefrom on a conventional television receiver but prevent that video signal from being copied on a conventional video recorder, said apparatus comprising vertical pulse generating means for generating less than a standard number of vertical pulses in each vertical period of the vertical synchronizing interval;

shift means for selectively shifting the beginning of selected vertical periods;

equalizing pulse generating means for generating less than a standard number of post equalizing pulses in each vertical synchronizing interval; and

combining means for combining the video signal with the generated vertical and post equalizing pulses, whereby a vertical synchronizing circuit of a television receiver is inhibited from locking onto the vertical synchronizing interval of said video signal and thereby generate vertical control signals at said fixed, standard period, and whereby perturbations in the displayed video picture attributed to a change in the frame period of the video signal are minimized.

42. The apparatus of claim 41 wherein the vertical pulse generating means comprises means for generating a series of vertical pulses, and inhibit means for inhibiting at least one of the vertical pulses in said series.

43. The apparatus of claim 42 wherein the vertical pulses in said series are generated at the beginning and at the midpoint of predetermined line intervals, and said inhibiting means comprises means for inhibiting the last midpoint-generated vertical pulse in said series.

44. The apparatus of claim 41 wherein the equalizing pulse generating means comprises means for generating a series of post equalizing pulses, and inhibit means for inhibiting selected post equalizing pulses in said series.

45. The apparatus of claim 44 wherein the post equalizing pulses in said series are generated at the beginning and at the midpoint of predetermined line intervals, and said inhibit means comprises means for inhibiting the midpoint-generated post equalizing pulses in said series.

46. The apparatus of claim 41 wherein the shift means comprises means for shifting the time of occurrence of the first vertical pulse in selected vertical periods.

47. The apparatus of claim 46 wherein said selected vertical periods comprise the vertical periods in FIELD II intervals of the video signal.

48. The apparatus of claim 46 wherein the means for shifting shifts the time of occurrence of the first vertical pulse by no more than half a line interval.

49. The apparatus of claim 46 wherein the means for shifting the time of occurrence of the first vertical pulse comprises advance means for advancing said time of occurrence when the frame period of the video signal increases and delay means for delaying said time of occurrence when the frame period of said video signal decreases.

50. The apparatus of claim 49 wherein said vertical pulse generating means comprises means for generating a start vertical pulse at a predetermined location in said vertical synchronizing interval;

a source of clock pulses;

count means for commencing the count of said clock pulses in response to said start vertical pulse;

means for sensing when the clock pulse count reaches a predetermined count; and

means for generating a vertical pulse commencing with said start vertical pulse and ending when said predetermined count is reached.

51. The apparatus of claim 50 wherein said advance means comprises means for advancing the location in the vertical synchronizing interval at which said start vertical pulse is generated, and said delay means comprises means for delaying the location in the vertical synchronizing interval at which said start vertical pulse is generated.

52. Apparatus for generating pre-equalizing, post-equalizing and vertical pulses for insertion into the vertical synchronizing interval of a transmitted video signal, comprising line count means for counting horizontal line intervals in each field of the video signal;

start equalizing means for generating start equalizing representations representing the start of respective pre-equalizing and post-equalizing pulses at predetermined line counts and for omitting selected ones of the start equalizing representations at preselected line counts;

start vertical means for generating start vertical representations representing the start of respective vertical pulses at other predetermined line counts and for omitting selected ones of the start vertical representations at preselected ones of said other line counts;

a source of clock signals;

clock counting means for counting clock signals in response to each start equalizing representation and each start vertical representation to produce clock counts;

sense means for sensing when the clock count reaches a first count following a start equalizing representation and a second count following a start vertical representation;

equalizing pulse generating means for generating equalizing pulses of durations determined by said first count; and

vertical pulse generating means for generating vertical pulses of durations determined by said second count, whereby equalizing and vertical pulses are not generated when start equalizing and start vertical representations are omitted.

53. The apparatus of claim 52 wherein said start equalizing means comprises means for generating a start equalizing representation at the beginning and at the midpoint of those horizontal line intervals corresponding to said predetermined line counts and means for omitting the start equalizing representations at the midpoint of the line intervals corresponding to at least some post-equalizing line counts.

54. The apparatus of claim 52 wherein said start vertical means comprises means for generating a start vertical representation at the beginning and at the midpoint of those horizontal line intervals corresponding to said other predetermined line counts and means for omitting the start vertical representation at the midpoint of the line interval corresponding to at least one of said other predetermined counts.

55. The apparatus of claim 54 wherein the video signal exhibits a changing frame period which varies above and below a fixed standard period, and wherein said start vertical means further comprises means for advancing the location of the first start vertical representation when the frame period increases and means for delaying the location of the first start vertical representation when the frame period decreases.

56. The apparatus of claim 55 wherein the first start vertical representation is respectively advanced or delayed on the order of about one-third the duration of a horizontal line interval.

57. The apparatus of claim 56 wherein said sense means further comprises means for sensing when the clock count reaches a third count following an advanced first start vertical representation and a fourth count following a delayed first start vertical representation;

and wherein said vertical pulse generating means includes means for generating a first vertical pulse of duration determined by the third or fourth count.

58. Apparatus for preventing counting circuitry included in the vertical synchronizing circuit of a video receiver from generating vertical control signals at a fixed, standard rate when a video signal transmitted to said video receiver exhibits a changing field interval which varies above and below a fixed, standard period, said apparatus comprising profile generating means for generating a profile representing the characteristics of said changing field interval, including the rate at which said field interval changes and the maximum and minimum periods of said field interval;

control means for varying said field interval in accordance with said profile such that said field interval is equal to said standard period for no more than a limited number of successive field intervals; and

means for transmitting the varying field interval.