Scrambling and descrambling of video signals using horizontal line combinations

• US 5,617,475 A
• Filed: 11/18/1994
• Issued: 04/01/1997
• Est. Priority Date: 11/18/1994
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Marz, Daniel
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/342,301
• Time in Patent Office: 865 Days
• Field of Search: 380/7, 380/11, 380/14, 380/17
• US Class Current: 380/205
• CPC Class Codes: H04N 7/1696 by changing or reversing the order of active picture signal portions

Abstract

A plurality of video lines in a raster scan video image are scrambled by delaying a first video line in time equal to the horizontal line scan time for the raster scan video field to produce a delayed first video line. The delayed first video line is inverted to produce an inverted delayed first video line and one of the delayed first video line, the inverted delayed first video line and a null signal is added to a second horizontal video line to produce a horizontal line of a scrambled video signal. The scrambled horizontal lines of video information are descrambled by delaying a first scrambled horizontal video line in time equal to the horizontal line scan time for the raster scan video field to produce a delayed first scrambled video line. The delayed first scrambled video line is inverted to produce an inverted delayed first scrambled video line and one of the delayed first scrambled video line, the inverted delayed first scrambled video line and a null signal is added to a second scrambled horizontal video line and to a feedback signal to produce a descrambled horizontal video line.

Claims

1. A method of scrambling a video signal having first and second components to produce a scrambled video signal, comprising the steps of:

delaying the first component in time to produce a delayed first component; and

combining the second component with the delayed first component to produce the scrambled video signal.

2. The method of claim 1, wherein the step of combining includes the step of adding the second component to the delayed first component.

3. The method of claim 1, wherein the step of combining includes the step of subtracting one of the delayed first component and the second component from the other of the delayed first component and the second component.

4. The method of claim 1, wherein the first component comprises an active video portion of a first horizontal video line and the second component comprises an active video portion of a second horizontal video line.

5. A method of descrambling a scrambled video signal having first and second scrambled components to produce a first component of a descrambled video signal having first and second components, comprising the steps of:

delaying the first scrambled component in time;

combining the delayed first scrambled component, the second scrambled component and a feedback signal to produce the first component of the descrambled video signal; and

delaying the second component of the descrambled video signal in time to produce the feedback signal.

6. The method of claim 5, wherein the step of combining includes the steps of identifying one of the second scrambled component and the delayed first scrambled component as a first signal, identifying the other of the second scrambled component and the delayed first scrambled component as a second signal, inverting the first signal, choosing one of the first signal and the inverted first signal and adding the chosen one of the first signal and the inverted first signal to the second signal.

7. The method of claim 6, wherein the step of combining further includes the steps inverting the delayed second component of the descrambled video signal, choosing one of the delayed second component and the inverted delayed second component and adding the chosen one of the delayed second component and the inverted delayed second component to the second signal.

8. The method of claim 5, wherein the first scrambled component comprises an active video portion of a first scrambled horizontal video line and the second scrambled component comprises an active video portion of a second scrambled horizontal video line.

9. A method of scrambling a plurality of video lines in a raster scan video image for a video field comprising the steps of:

(1) delaying a first video line in a time equal to the horizontal line scan time for the raster scan video field to produce a delayed first video line;

(2) inverting the delayed first video line to produce an inverted delayed first video line;

(3) selecting one of,

(a) the delayed first video line, or

(b) the inverted delayed first video line, or

(c) a zero-level signal

(4) adding a second video line to the selected one of (a), (b), or (c); and

(5) repeating steps (1)-(4) for each of the plurality of video lines of the video field.

10. The method of claim 9, further including the step of encoding a video line with scrambling information indicative of the signal selected in the step of selecting.

11. The method of claim 9, further including the step of adding a scrambling signal onto each of the plurality of video lines before the step of delaying the first video line.

12. A method of descrambling a plurality of scrambled video lines in a raster scan video image for a video field comprising the steps of:

(1) delaying a first scrambled video line an amount of time equal to the horizontal line scan time for the raster scan video field to provide a delayed first scrambled video line;

(2) inverting the delayed first scrambled video line to provide an inverted delayed first scrambled video line;

(3) selecting one of,

(a) the delayed first scrambled video line, or

(b) the inverted delayed first scrambled video line, or

(c) a zero-level signal

(4) adding a second scrambled video line to the selected one of (a), (b), or (c) and to a feedback signal to produce a descrambled video line;

(5) developing the feedback signal from a delayed descrambled video line; and

(6) repeating steps (1)-(5) for each of the plurality of scrambled video lines of the video field.

13. The method of claim 12, wherein the step of developing the feedback signal includes the steps of inverting the delayed descrambled video line and choosing one of (a) the delayed descrambled video line, or (b) the inverted delayed descrambled video line, or (c) a zero-level signal, as the feedback signal.

14. The method of claim 13, wherein the scrambled video signal includes scrambling information indicative of the manner in which scrambled video signal was scrambled and including the steps of detecting the scrambling information and using the detected scrambling information in the steps of selecting and choosing.

15. The method of claim 14, wherein the scrambled video signal includes a scrambling signal added thereto and including the step of removing the scrambling signal from the descrambled video line after the step of adding.

16. An apparatus for scrambling a video signal having first and second components to produce a scrambled video signal, including:

means for delaying the first component in time to produce a delayed first component;

means coupled to the delaying means for combining the second component with the delayed first component to produce the scrambled video signal.

17. The apparatus of claim 16, wherein the combining means includes means for adding the second component to the delayed first component.

18. The apparatus of claim 16, wherein the combining means includes means for subtracting one of the delayed first component and the second component from the other of the delayed first component and the second component.

19. The apparatus of claim 16, wherein the combining means includes means for inverting one of the second component and the delayed first component to produce an inverted second component or an inverted delayed first component and means for adding one of the following groups:

(a) the second component and the delayed first component, or

(b) the second component and the inverted delayed first component, or

(c) the inverted second component and the delayed first component.

20. The apparatus of claim 19, wherein the combining means further includes means for choosing the second component as the scrambled video signal.

21. The apparatus of claim 19, wherein the first component comprises an active video portion of a first horizontal video line and the second component comprises an active video portion of a second horizontal video line.

22. The apparatus of claim 21, wherein the combining means includes means for inverting the delayed first component, means for choosing one of (a) the delayed first component, or (b) the inverted delayed first component, or (c) a zero-level signal, and means for adding the second component to the chosen one of the delayed first component, the inverted delayed first component or the null signal.

23. The apparatus of claim 16, wherein the video signal has a horizontal line scan time for a raster scan video field and the delaying means delays the first component an amount in time equal to the horizontal line scan time for the raster scan video field.

24. The apparatus of claim 16, further including means coupled to the delaying means for adding a scrambling signal onto one of the first component and the second component.

25. The apparatus of claim 16, further including means coupled to the combining means for adding scrambling information indicative of the operation of the combining means to the scrambled video signal.

26. An apparatus for descrambling a scrambled video signal having first and second scrambled components to produce a first component of a descrambled video signal having first and second components, comprising:

means for delaying the first scrambled component in time;

means for combining the delayed first scrambled component, the second scrambled component and a feedback signal to produce the first component of the descrambled video signal; and

means responsive to the second component of the descrambled video signal for producing the feedback signal.

27. The apparatus of claim 26, wherein the combining means includes means for adding the delayed first scrambled component and the second scrambled component.

28. The apparatus of claim 26, wherein the combining means includes means for subtracting one of the delayed first scrambled component and the second scrambled component from the other of the delayed first scrambled component and the second scrambled component.

29. The apparatus of claim 26, wherein the combining means includes means for inverting one of the second scrambled component and the delayed first scrambled component to produce an inverted second scrambled component or an inverted delayed first scrambled component and means for adding one of the following groups:

(a) the second scrambled component and the delayed first scrambled component, or

(b) the second scrambled component and the inverted delayed first scrambled component, or

(c) the inverted second scrambled component and the delayed first scrambled component.

30. The apparatus of claim 29, wherein the producing means includes further delaying means for delaying the second component of the descrambled video signal.

31. The apparatus of claim 30, wherein the delaying means delays the first scrambled component a first amount of time and the further delaying means delays the second component of the descrambled video signal an amount of time equal to twice the first amount of time.

32. The apparatus of claim 30, wherein the producing means includes further means for inverting the delayed second component of the descrambled video signal and means for choosing one of the delayed second component of the descrambled video signal and the inverted delayed second component of the descrambled video signal as the feedback signal.

33. The apparatus of claim 32, wherein the producing means includes further means for choosing a zero-level signal as the feedback signal.

34. The apparatus of claim 33, wherein the first scrambled component comprises an active video portion of a first scrambled horizontal video line and the second scrambled component comprises an active video portion of a second scrambled horizontal video line.

35. The apparatus of claim 26, wherein one of the first and second scrambled components includes a scrambling signal added thereto and including means coupled to the combining means for removing the scrambling signal from the first component of the descrambled video signal.

36. The apparatus of claim 26, wherein the scrambled video signal includes scrambling information indicative of the manner in which the scrambled video signal was generated and including means for detecting the scrambling information indicative of the manner in which the scrambled video signal was generated, wherein the combining means and the producing means are responsive to the detected scrambling information indicative of the manner in which the scrambled video signal was generated.

37. A method of transmitting a video signal having first and second original components to develop a reproduced video signal having first and second reproduced components, comprising the steps of:

delaying the first original component of the video signal in time to produce a delayed first original component;

combining the second original component of the video signal with the delayed first original component to produce a portion of a scrambled video signal having first and second scrambled components;

transmitting the scrambled video signal;

receiving the transmitted scrambled video signal;

delaying the first scrambled component of the received scrambled video signal in time;

combining the delayed first scrambled component of the received scrambled video signal, the second scrambled component of the received scrambled video signal and a feedback signal to develop the first reproduced component of the reproduced video signal; and

delaying the second reproduced component of the reproduced video signal to produce the feedback signal.

38. The method of claim 37, wherein the step of combining the second original component of the video signal with the delayed first original component includes one of the steps of adding the second original component to the delayed first original component and subtracting one of the second original component and the delayed first original component from the other of the second original component and the delayed first original component, wherein the step of combining the delayed first scrambled component of the received scrambled video signal, the second scrambled component of the received scrambled video signal and a feedback signal includes one of the steps of adding the second scrambled component to the delayed first scrambled component and subtracting one of the second scrambled component and the delayed first scrambled component from the other of the second scrambled component and the delayed first scrambled component and wherein the step of combining the delayed first scrambled component of the received scrambled video signal, the second scrambled component of the received scrambled video signal and a feedback signal further includes the steps of inverting the delayed second reproduced component and choosing one of the delayed second reproduced component and the inverted delayed second reproduced component as the feedback signal.