Transparent embedment of data in a video signal

• US 6,211,919 B1
• Filed: 03/28/1997
• Issued: 04/03/2001
• Est. Priority Date: 03/28/1997
• Status: Expired due to Term

• Current Assignee: Tektronix Incorporated (Fortive Corp.)
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Zink, Scott E., Baker, Daniel G.
• Primary Examiner(s): Peng, John
• Assistant Examiner(s): Desir, Jean W.
• Application Number:
  US08/829,524
• Time in Patent Office: 1,467 Days
• Field of Search: 348/473, 348/142, 348/461, 348/474, 348/475, 348/486, 348/398, 348/476-479, 380/7, 380/10-20, 398/462, 398/474
• US Class Current: 348/473
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/0077 Multicode, e.g. multiple codes assigned to one user
• CPC Class Codes: H04L 5/04 the signals being represented by different amplitudes or polarities, e.g. quadriplex
• CPC Class Codes: H04N 7/24 Systems for the transmission of television signals using pulse code modulation H04N21/00 takes precedence

Abstract

A method and apparatus for transparently embedding data into a video signal modulates a particular carrier frequency with a randomized pattern representing the data. The randomized pattern may be a combination of the data with the output from a pseudo-random binary sequence generator, or the data may be converted first into a bi-orthogonal pattern selected from among a plurality of such patterns and then randomized. The resulting modulated carrier frequency is then amplitude modulated based upon a human visual model so that the modulated carrier frequency amplitude is greater in areas of high image complexity and lower in areas of low image complexity. The subliminal data represented by the modulated carrier frequency is added to the video signal. At a decoder the data is recovered using appropriate correlation techniques by first filtering the video signal to increase the subliminal data component relative to the image component, then demodulating the data component to produce the data pattern, and then correlating the data pattern with the possible data patterns to identify the particular pattern and associated data word.

Claims

1. An apparatus for transparently encoding data within a video signal comprising:

means for generating from the data to be encoded and video timing signals associated with the video signal a spread spectrum, two-dimensional randomized binary noise-like pattern;

means for modulating the randomized binary pattern onto a carrier frequency to produce a subliminal data signal; and

means for combining the subliminal data signal with the video signal to produce an output video signal having the data transparently encoded within the video signal.

2. The apparatus as recited in claim 1 wherein the data to be encoded comprises a representation of an audio signal for detecting and correcting relative audio to video timing at a receiver to maintain sound to video synchronization as encoded at a source.

3. The apparatus as recited in claim 1 wherein the data to be encoded comprises digital signature authentication information for identifying a source of the video signal.

4. The apparatus as recited in claim 1 wherein the data to be encoded comprises an identifier for a motion test sequence to be captured for video quality assessment.

9. The apparatus as recited in claims 1, 5 or 8 further comprising means for softening edges in the subliminal data signal prior to the combining means.

5. An apparatus for transparently encoding data within a video signal comprising:

means for generating from the data to be encoded and video timing signals associated with the video signal a spread spectrum randomized binary pattern;

means for modulating the spread spectrum randomized binary pattern onto a carrier frequency to produce a subliminal data signal;

means for alternating the phase of the subliminal data signal on alternate lines of each frame of the video signal such that each pair of contiguous lines has the same data but inverted in polarity; and

means for combining the subliminal data signal with the video signal to produce an output video signal having the data transparently encoded within the video signal.

6. The apparatus as recited in claim 5 wherein the alternating means comprises:

means for dividing a specific one of the video timing signals by two to produce a phase inversion control signal; and

means for inverting the phase of the subliminal data signal on alternate lines of each frame in response to the phase inversion signal.

7. The apparatus as recited in claim 6 wherein for an interlaced version of the video signal the specific one of the video timing signals is a field rate signal and for a progressive scan version of the video signal the specific one of the video timing signals is a line rate signal.

8. An apparatus for transparently encoding data within a video signal comprising:

means for generating from the data to be encoded and video timing signals associated with the video signal a spread spectrum randomized binary pattern;

means for modulating the spread spectrum randomized binary pattern onto a carrier frequency to produce a subliminal data signal;

means for amplitude modulating the subliminal data signal with a gain signal based upon a human visual model; and

means for combining the subliminal data signal with the video signal to produce an output video signal having the data transparently encoded within the video signal.

10. A method of transparently encoding data within a video signal comprising the steps of:

generating from the data to be encoded and video timing signals associated with the video signal a spread spectrum, two-dimensional randomized binary noise-like pattern;

modulating the randomized binary pattern onto a carrier frequency to produce a subliminal data signal; and

combining the subliminal data signal with the video signal to produce an output video signal having the data transparently encoded within the video signal.

11. The method as recited in claim 10 further comprising the step of shuffling the data two-dimensionally to provide channel coding.

12. The method as recited in claim 10 further comprising the step of shuffling the data three-dimensionally to provide channel coding.

13. The method as recited in claim 10 wherein the data to be encoded comprises a representation of an audio signal for detecting and correcting relative audio to video timing at a receiver to maintain sound to video synchronization as encoded at a source.

14. The method as recited in claim 10 wherein the data to be encoded comprises digital signature authentication information for identifying a source of the video signal.

15. The method as recited in claim 10 wherein the data to be encoded comprises an identifier for a motion test sequence to be captured for video quality assessment.

20. The method as recited in claims 10, 16 or 19 further comprising the step of softening edges in the subliminal data signal prior to the combining step.

16. A method of transparently encoding data within a video signal comprising the steps of:

generating from the data to be encoded and video timing signals associated with the video signal a spread spectrum randomized binary pattern;

modulating the spread spectrum randomized binary pattern onto a carrier frequency to produce a subliminal data signal;

alternating the phase of the subliminal data signal on alternate lines of each frame of the video signal such that each pair of contiguous lines has the same data but inverted in polarity; and

combining the subliminal data signal with the video signal to produce an output video signal having the data transparently encoded within the video signal.

17. The method as recited in claim 16 wherein the alternating step comprises the steps of:

dividing a specific one of the video timing signals by two to produce a phase inversion control signal; and

inverting the phase of the subliminal data signal on alternate lines of each frame in response to the phase inversion signal.

18. The method as recited in claim 17 wherein for an interlaced version of the video signal the specific one of the video timing signals is a field rate signal and for a progressive scan version of the video signal the specific one of the video timing signals is a line rate signal.

19. A method of transparently encoding data within a video signal comprising the steps of:

generating from the data to be encoded and video timing signals associated with the video signal a spread spectrum randomized binary pattern;

modulating the spread spectrum randomized binary pattern onto a carrier frequency to produce a subliminal data signal;

amplitude modulating the subliminal data signal with a gain signal based upon a human visual model; and

combining the subliminal data signal with the video signal to produce an output video signal having the data transparently encoded within the video signal.

21. An apparatus for transparently embedding data within a video signal comprising:

a pattern generator having as inputs timing signals associated with the video signal and the data to be embedded and producing as an output a spread spectrum, two-dimensional randomized pattern noise-like signal;

a modulator having as inputs the randomized pattern signal and a carrier frequency synchronized with the randomized pattern signal and producing as an output a subliminal data signal; and

a combiner having as inputs the subliminal data signal and the video signal and producing as an output a transparently embedded data video signal.

22. The apparatus as recited in claim 21 wherein the pattern generator comprises:

a data pattern generator having as inputs the data to be embedded and the timing signals and producing as an output a binary pattern;

a pseudo random binary sequence generator having as an input one of the timing signals and producing as an output a random binary sequence;

a combination circuit having as inputs the binary pattern and the random binary sequence and producing as an output the randomized binary pattern.

23. The apparatus as recited in claim 22 wherein the data pattern generator comprises a circular shift register having as inputs the data and the timing signals and producing as an output the binary pattern.

24. The apparatus as recited in claim 23 wherein the data pattern generator further comprises a pattern encoder having the output from the circular shift register and the timing signals as inputs and producing as an output the binary pattern.

25. The apparatus as recited in claim 24 wherein the data pattern generator provides a plurality of bi-orthogonal binary patterns, with the one selected for output as the binary pattern being determined by the output from the circulating shift register.

26. The apparatus as recited in claim 24 wherein the data pattern generator comprises a Walsh encoder having as input the output from the circular shift register and producing as an output the binary pattern selected from among a plurality of bi-orthogonal patterns.

27. The apparatus as recited in claim 21 wherein the combination circuit comprises an exclusive OR gate having as inputs the binary pattern and the random binary sequence and producing as an output the randomized binary pattern.

32. The apparatus as recited in claims 21, 28 or 31 further comprising an amplitude modulator having as inputs the subliminal data signal and a gain control signal based upon a human visual model and producing as an output an amplitude modulated subliminal data signal as the subliminal data signal for input to the combiner.

34. The apparatus as recited in claim 32 further comprising:

a highpass human visual model filter having as an input the video signal and producing as an output a highpass filtered video signal representing high spatial detail;

a lowpass human visual model filter having as an input the video signal and producing as an output a lowpass filtered video signal representing local contrast; and

a combining circuit having as inputs the lowpass and highpass filtered video signals and producing as an output the gain signal.

35. The apparatus as recited in claim 34 further comprising a temporal human visual model filter having as an input the video signal and producing as an output a temporally filtered video signal, the temporally filtered video signal being applied as another input to the combining circuit so that the gain signal is a combination of the lowpass, highpass and temporally filtered video signals.

36. The apparatus as recited in claim 32 wherein the amplitude modulator is inserted between the modulator and the softening filter.

37. The apparatus as recited in claim 32 wherein the amplitude modulator is inserted between the softening filter and the combiner.

38. The apparatus as recited in claims 21, 28, or 31 further comprising a forward error correction circuit having as an input the data to be transparently encoded within the video signal and producing as an output a forward corrected data signal coupled to the input of the pattern generator.

28. An apparatus for transparently embedding data within a video signal comprising:

a pattern generator having as inputs timing signals associated with the video signal and the data to be embedded and producing as an output a spread spectrum randomized pattern signal;

a modulator having as inputs the spread spectrum randomized binary signal and a carrier frequency synchronized with the spread spectrum randomized pattern signal and producing as an output a subliminal data signal;

a phase alternator circuit having as inputs a specific one of the video timing signals and a component of the subliminal data signal and having as an output a signal that produces inversion of the phase of the subliminal data signal on alternate lines of each frame of the video signal such that each pair of contiguous lines has the same data but inverted in polarity; and

a combiner having as inputs the subliminal data signal and the video signal and producing as an output a transparently embedded data video signal.

29. The apparatus as recited in claim 28 wherein the phase alternator circuit comprises:

a divide-by-two circuit having as an input the specific one of the video timing signals and having as an output a phase inversion control signal; and

an exclusive OR gate having as inputs the phase inversion control signal and the component of the subliminal data signal and having as an output the signal for inverting the phase of the subliminal data signal.

30. The apparatus as recited in claim 29 wherein for an interlaced version of the video signal the specific one of the video timing signals is a field rate signal and for a progressive scan version of the video signal the specific one of the video timing signals is a line rate signal.

31. An apparatus for transparently encoding data within a video signal comprising:

a pattern generator having as inputs timing signals associated with the video signal and the data to be embedded and producing as an output a spread spectrum randomized pattern signal;

a modulator having as inputs the spread spectrum randomized pattern signal and a carrier frequency synchronized with the spread spectrum randomized pattern signal and producing as an output a subliminal data signal;

a softening filter having as an input the subliminal data signal and producing as an output a filtered subliminal data signal; and

a combiner having as inputs the filtered subliminal data signal and the video signal and producing as an output a transparently embedded data video signal.

33. The apparatus as recited in claim 31 wherein the softening filter comprises:

a horizontal bandpass filter centered on the carrier frequency having as an input the subliminal data signal and producing as an output a horizontally filtered subliminal data signal; and

a vertical lowpass filter having as an input the horizontally filtered subliminal data signal and producing as an output the filtered subliminal data signal.

39. An apparatus for extracting transparently embedded data from a video signal where the embedded data is a spread spectrum, two-dimensional randomized binary noise-like pattern modulated onto a carrier frequency comprising:

means for demodulating the video signal about the carrier frequency with a random binary sequence modulated carrier frequency to produce a broadband video signal; and

means for correlating the broadband video signal with a plurality of binary patterns to recover the embedded data.

40. An apparatus for extracting transparently embedded data from a video signal where the embedded data is a spread spectrum randomized binary pattern modulated onto a carrier frequency that is repeated on alternate lines of each frame of the video signal with opposite phase comprising:

means for filtering the video signal to enhance the embedded data with respect to the video content of the video signal;

means for demodulating the filtered video signal about the carrier frequency with a pseudo-random binary sequence modulated carrier frequency to produce a broadband video signal; and

means for correlating the broadband video signal with a plurality of binary patterns to recover the embedded data.

41. The apparatus as recited in claim 40 wherein the filtering means comprises:

means centered on the carrier frequency for broadband filtering the video signal to produce a first filtered video signal; and

means for comb filtering the first filtered video signal to produce the video signal for input to the demodulating means.

42. A method of extracting transparently embedded data from a video signal where the embedded data is a spread spectrum, two-dimensional randomized binary noise-like pattern modulated onto a carrier frequency comprising the steps of:

demodulating the video signal about the carrier frequency with a random binary sequence modulated carrier frequency to produce a broadband video signal; and

correlating the broadband video signal with a plurality of binary patterns to recover the embedded data.

43. A method of extracting transparently embedded data from a video signal where the embedded data is a spread spectrum randomized binary pattern modulated onto a carrier frequency that is repeated on alternate lines of each frame of the video signal with opposite phase comprising the steps of:

filtering the video signal to enhance the embedded data with respect to the video content of the video signal;

demodulating the video signal about the carrier frequency with a pseudo-random binary sequence modulated carrier frequency to produce a broadband video signal; and

correlating the broadband video signal with a plurality of binary patterns to recover the embedded data.

44. The method as recited in claim 43 wherein the filtering step comprises the steps of:

broadband filtering the video signal about the carrier frequency to produce a first filtered video signal; and

comb filtering the first filtered video signal to produce the video signal for input to the demodulating step.

45. An apparatus for extracting transparently embedded data from a video signal where the embedded data is a spread spectrum, two-dimensional randomized binary noise-like pattern modulated onto a carrier frequency comprising:

a demodulator having as inputs a random binary sequence modulated carrier frequency and the video signal and producing as an output a broadband video signal; and

a correlation receiver having as inputs the broadband video signal and timing signals associated with the video signal for comparing the broadband video signal with a plurality of binary patterns to recover as an output the embedded data.

46. The apparatus as recited in claim 45 wherein the demodulator comprises:

a pseudo random binary sequence generator having as an input one of the timing signals and providing as an output a random binary sequence;

a numerically controlled oscillator having as an input a control signal derived from the one timing signal and providing as an output the carrier frequency;

a first modulator having as inputs the carrier frequency and the random binary sequence and producing as an output a modulated carrier frequency; and

a second modulator having as inputs the video signal and the modulated carrier frequency and producing as an output the broadband video signal.

47. The apparatus as recited in claim 45 wherein the correlation receiver comprises:

a sampler having as an input the broadband video signal and producing as an output a sampled video signal;

a pattern buffer having as inputs the timing signals and providing as outputs in parallel a plurality of binary patterns;

a plurality of correlation circuits in parallel, each having as inputs the sampled video signal and a specific one of the plurality of binary patterns and producing as an output a specific correlation coefficient; and

a magnitude comparator having as inputs the correlation coefficients from each correlation circuit and producing as an output a binary data word representing the sign and value of the greatest of the correlation coefficients, the binary data word being the embedded data.

48. An apparatus for extracting transparently embedded data from a video signal where the embedded data is a spread spectrum randomized binary pattern modulated onto a carrier frequency that is the same on alternate lines of each frame of the video signal with opposite phase comprising:

a filter having as an input the video signal and producing as an output a filtered video signal, the filter enhancing the embedded data with respect to the video content of the video signal;

a demodulator having as inputs a pseudo-random binary sequence modulated carrier frequency and the filtered video signal and producing as an output a broadband video signal; and

a correlation receiver having as inputs the broadband video signal and timing signals associated with the video signal for comparing the broadband video signal with a plurality of binary patterns to recover as an output the embedded data.

49. The apparatus as recited in claim 48 wherein the filter comprises:

a broadband filter centered on the carrier frequency having as an input the video signal and producing as an output a first filtered video signal; and

a field comb filter having as an input the first filtered video signal and producing as an output the filtered video signal coupled to the input of the demodulator.