Copy protection for digital motion picture image data

• US 7,043,019 B2
• Filed: 02/28/2001
• Issued: 05/09/2006
• Est. Priority Date: 02/28/2001
• Status: Active Grant

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Tehranchi, Babak, Jones, Paul W.
• Primary Examiner(s): Revale, Christopher
• Assistant Examiner(s): Chen, Shin-Hon
• Application Number:
  US09/796,201
• Publication Number:
  US 20020168069A1
• Time in Patent Office: 1,896 Days
• Field of Search: 380/218, 380/15, 380/10, 380/19, 380/202, 380/252, 380/201, 380/205, 380/221, 380/238, 380/17, 352/40, 382/100, 382/284, 382/248, 382/232, 713/176, 358/3.28
• US Class Current: 380/218
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0085 Time domain based watermarking, e.g. watermarks spread over several images
• CPC Class Codes: G06T 2201/0064 for copy protection or copy management, e.g. CGMS, copy only once, one-time copy
• CPC Class Codes: H04N 2005/91357 by modifying the video signal
• CPC Class Codes: H04N 2005/91392 using means for preventing making copies of projected video images
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• CPC Class Codes: H04N 9/3179 Video signal processing therefor

Abstract

An apparatus and method for displaying a copy-deterrent pattern (104) within a digital motion picture in order to discourage recording of the motion picture using a video camera or other sampling recording device. A copy-deterrent pattern (104) could be, for example, one or more symbols, a random pattern, a digital watermark or a text message (106). The copy-deterrent pattern (104) comprises a plurality of pixels within each frame of the digital motion picture, and the displayed pixel intensities are modulated at a temporal frequency using modulation characteristics deliberately selected to be imperceptible to human observers while simultaneously producing objectionable aliasing in any copy made using a video camera.

Claims

1. A copy-deterrent display apparatus for displaying a sequential plurality of image frames of a digital motion picture, each of said image frames comprising an array of pixels, each said pixel assigned to be displayed at a predetermined intensity within each frame, said apparatus comprising:

(a) a pattern generator/modulator assembly capable of providing control signals specifying a pattern of pixels within each said frame, said control signals specifying temporal modulation of said pattern of pixels at predetermined frequency or frequencies within a frame period so that each of certain pixels are multiply pulsed during a frame period, wherein said temporal modulation is chosen to be at a frequency imperceptible to a human observer observing the digital motion picture displayed on said display apparatus while simultaneously producing objectionable artifacts selected from the group consisting of an obscuring pattern, an obscuring message and a watermark due to image aliasing when said displayed frames are captured by a sampling video capturing device wherein said image aliasing results from the presence of relatively strong temporal frequency components that are within the visible frequency range when captured by the video capturing device; and

(b) an image forming assembly capable of accepting said control signals from said pattern generator/modulator assembly and of modifying the displayed pixel intensities within each said frame in response to said control signals.

2. The apparatus of claim 1 wherein said modulated pattern of pixels comprises a text message.

3. The apparatus of claim 1 wherein said modulated pattern of pixels comprises a predetermined copy obscuration pattern.

4. The apparatus of claim 1 wherein said modulated pattern of pixels comprises a random pattern.

5. The apparatus of claim 1 wherein said modulated pattern of pixels comprises a digital watermark.

6. The apparatus of claim 1 wherein said modulated pattern of pixels substantially comprises said frame.

7. The apparatus of claim 1 wherein said image forming assembly uses a spatial light modulator to display said pixels within said frames.

8. The apparatus of claim 7 wherein said spatial light modulator comprises a liquid-crystal device.

9. The apparatus of claim 7 wherein said spatial light modulator comprises a digital multimirror device.

10. The apparatus of claim 7 wherein said spatial light modulator comprises an emissive display device.

11. The apparatus of claim 1 wherein said temporal modulation encodes a digital watermark.

12. The apparatus of claim 1 wherein said output control signals condition digital data within said image forming assembly.

13. The apparatus of claim 1 wherein said output control signals condition analog signal levels within said image forming assembly.

14. The apparatus of claim 1 wherein said output control signals condition an optical path within said image forming assembly.

15. The apparatus of claim 14 wherein said optical path modulates said pattern of pixels using a shutter.

16. The apparatus of claim 14 wherein said optical path modulates said pattern of pixels using a spatial light modulation mask.

17. A method for displaying a digital motion picture that is provided with a copy-deterrent pattern in a sequential plurality of image frames of the digital motion picture, each of said image frames comprising an array of pixels, said pattern comprising a plurality of pixels selected from said frame, the method comprising temporally modulating said pattern by multiple pulsing of selected pixels within a frame period wherein said temporal modulation is chosen to be at a frequency or frequencies imperceptible to a human observer observing the digital motion picture displayed on a display apparatus while simultaneously producing objectionable artifacts selected from the group consisting of an obscuring pattern, an obscuring message and a watermark due to aliasing when said displayed frames are captured by a sampling video capturing device wherein said image aliasing results from the presence of relatively strong temporal frequency components that are within the visible frequency range when captured by the video capturing device.

18. The method of claim 17 wherein said copy deterrent pattern comprises a message.

19. The method of claim 17 wherein said copy deterrent pattern comprises a predetermined copy obscuration pattern.

20. The method of claim 17 wherein said copy deterrent pattern comprises a random pattern.

21. The method of claim 17 wherein said copy deterrent pattern comprises a digital watermark.

22. The method of claim 17 wherein said copy deterrent pattern substantially comprises said frame.

23. The method of claim 17 wherein the plurality of image frames form part of a digital movie or video image having a predetermined refresh rate and wherein said pattern is temporally modulated at a frequency higher than the refresh rate.

24. The method of claim 23 and wherein the temporal modulation is sinusoidal.

25. The method of claim 24 and wherein intensity of the pixels comprising the modulated pattern is adjusted to compensate for the modulation.

26. The method of claim 23 and wherein the modulation is a rectangular wave.

27. The method of claim 26 and wherein intensity of the pixels comprising the modulated pattern is adjusted to compensate for the modulation.

28. The method of claim 23 and wherein one or more color components of an image in the frame is subject to said temporal modulation but other color components of the same image frame are not subject to said temporal modulation.

29. The method of claim 23 and wherein the pattern comprises a portion of an image frame.

30. The method according to claim 23 and wherein the pattern comprises plural portions and the plural portions are temporarily modulated at different frequencies from each other.

31. The method according to claim 23 and wherein the frequency of modulation is changed from one frequency to another frequency during the course of display.

32. The method according to claim 23 and wherein the plurality of pixels are analyzed according to a peak intensity criterion and pixels meeting the criterion further determine the pattern that is subject to the temporal modulation.

33. The method according to claim 23 and wherein in order to provide copy deterrence to a video capturing device having a sampling frequency of 60 Hertz and/or 120 Hertz a temporal modulation frequency is used that meets the criteria of the absolute value of the difference between the sampling frequency and the temporal modulation frequency is greater than or equal to 10 Hertz and less than or equal to 30 Hertz.

34. The method of claim 17 and wherein the temporal modulation is sinusoidal.

35. The method of claim 34 and wherein intensity of the pixels comprising the modulated pattern is adjusted to compensate for the modulation.

36. The method of claim 17 and wherein the modulation is a rectangular wave.

37. The method of claim 36 and wherein intensity of the pixels comprising the modulated pattern is adjusted to compensate for the modulation.

38. The method of claim 17 and wherein one or more color components of an image in the frame is subject to said temporal modulation but other color components of the same image frame are not subject to said temporal modulation.

39. The method of claim 17 and wherein the pattern comprises a portion of an image frame.

40. The method according to claim 17 and wherein the pattern comprises plural portions and the plural portions are temporarily modulated at different frequencies from each other.

41. The method according to claim 17 and wherein the frequency of modulation is changed from one frequency to another frequency during the course of display.

42. The method according to claim 17 and wherein the plurality of pixels are analyzed according to a peak intensity criterion and pixels meeting the criterion further determine the pattern that is subject to the temporal modulation.

43. The method according to claim 17 and wherein in order to provide copy deterrence to a video capturing device having a sampling frequency of 60 Hertz and/or 120 Hertz a temporal modulation frequency is used that meets the criteria of the absolute value of the difference between the sampling frequency and the temporal modulation frequency is greater than or equal to 10 Hertz and less than or equal to 30 Hertz.

44. The method of claim 17 and wherein the displayed pixel intensities are modulated so that an observer of the displayed movie will not see any degradation in image quality.

45. The method of claim 17 and wherein a random selection of pixels is used to produce the copy-deterrent pattern that is optimal for obscuring a video camera copy of the digital motion picture.

46. The method of claim 17 and wherein the copy-deterrent pattern is changed for each set of n frames.

47. The method of claim 17 and wherein pixels in an image frame are analyzed according to a peak intensity criterion and pixels meeting the criterion determine the pattern that is subject to the temporal modulation.

48. The method of claim 17 wherein the copy-deterrent pattern is encoded using amplitude modulation to encode the pattern within a sequence of variable intensity values.

49. A method for identifying a candidate modulation frequency to be applied to a selected pattern of pixels within a sequence of digital motion picture frames, said candidate modulation frequency intended to cause aliasing when the sequence of digital motion picture frames is sampled using a video capture device, said method comprising:

(a) selecting a plurality of sequential frames;

(b) obtaining intensity values for each pixel within said selected pattern of pixels;

(c) calculating a modulation intensity value for each said pixel within said selected pattern of pixels, said modulation intensity value conditioned by the duty cycle for a modulation signal waveform;

(d) calculating a bandwidth for said pixels within said selected pattern of pixels;

(e) choosing a target sampling frequency; and

(f) calculating said candidate modulation frequency based on said target sampling frequency and based on predetermined thresholds for visible modulation, said candidate modulation frequency selected based on having a first order or a second order side band within bounds of said predetermined thresholds for visible modulation.