Method and apparatus for embedding auxiliary data in a primary data signal

• US 5,937,000 A
• Filed: 12/06/1996
• Issued: 08/10/1999
• Est. Priority Date: 09/06/1995
• Status: Expired due to Term

• Current Assignee: Verance Corporation
• Original Assignee: Solana Technology Development Corp. (Verance Corporation)
• Inventors: Lee, Chong U., Moallemi, Kamran, Warren, Robert L.
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): Corrielus, Jean B.
• Application Number:
  US08/764,096
• Time in Patent Office: 977 Days
• Field of Search: 375/200, 375/206, 375/208, 375/267, 375/285, 375/296, 375/346, 375/347, 375/349, 375/350, 375/367, 375/241, 375/242, 370/335, 370/342, 370/493, 370/494, 370/495, 370/497, 370/527, 370/529, 395/2.28, 704/200, 704/201, 704/203, 704/214, 704/219, 704/262, 704/269
• US Class Current: 375/141
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: H04B 1/665 using psychoacoustic properties of the ear, e.g. masking effect
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 15/04 the interference being caused by substantially sinusoidal oscillations, e.g. in a receiver or in a tape-recorder
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• 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: H04J 7/00 Multiplex systems in which the amplitudes or durations of the signals in individual channels are characteristic of those channels
• CPC Class Codes: H04J 9/00 Multiplex systems in which each channel is represented by a different type of modulation of the carrier
• CPC Class Codes: H04J 99/00 Subject matter not provided for in other groups of this subclass

Abstract

Auxiliary data is transported in a primary data signal by hiding the data in the form of colored noise. The colored noise has a spectrum that simulates the spectrum of the primary data signal. The data to be transported is first converted to a spread spectrum signal. The primary data signal is analyzed to determine its spectral shape. The same spectral shape is imparted to the spread spectrum signal, which is then combined with the primary data signal for transmission. The spectral shaping can be performed using time domain modeling and synthesis such as linear predictive coding or by using subband coding techniques such as fast Fourier transforms. A plurality of different auxiliary information streams can be transported on the primary data signal. By adjusting the gain of individual spread spectrum signal carrier(s) and the power of the colored noise, the auxiliary information stream(s) can be rendered at a desired level at, below or above an interference threshold in the primary data signal.

Claims

1. A method for transporting auxiliary information in a primary data signal, comprising the steps of:

modulating a pseudorandom noise carrier by said auxiliary information to provide a spread spectrum signal carrying said information on a carrier portion thereof;

evaluating said primary data signal using time domain modeling to obtain an approximation of its spectral shape; and

using time domain synthesis which is responsive to said time domain modeling to provide the carrier portion of said spread spectrum signal with a spectral shape which simulates the spectral shape of said primary data signal, thereby producing a noise signal containing said auxiliary information to be carried in said primary data signal.

2. A method in accordance with claim 1, wherein:

said noise signal has an adjusted power so that it is provided at a desired level in said primary data signal; and

said power-adjusted noise signal is combined with said primary data signal to produce an output signal carrying said auxiliary information as noise in said primary data signal.

3. A method for recovering said auxiliary information from a received primary data signal carrying the noise signal of claim 1, comprising the steps of:

evaluating said received primary data signal using time domain modeling to approximate its spectral shape;

processing the received primary data signal, based on the approximate spectral shape determined therefore to whiten the noise signal contained therein; and

demodulating the whitened noise signal to recover said auxiliary information.

4. A method in accordance with claim 1, wherein said primary data signal comprises a stereo frequency-modulated signal which is modulated at a carrier frequency for transmission at said carrier frequency, comprising the further step of:

carrying said noise signal in at least one of;

(a) said stereo frequency-modulated signal prior to said modulation at said carrier frequency, and (b) said stereo frequency-modulated signal subsequent to said modulation at said carrier frequency.

5. A method in accordance with claim 3 wherein:

said received primary data signal comprises the sum of said noise signal and said primary data signal.

6. A method in accordance with claim 3 wherein:

said time domain modeling comprises linear predictive coding (LPC) to provide LPC coefficients for use during said using step and said whitening step.

7. A method in accordance with claim 6 wherein:

the LPC coefficients used during said whitening step are derived from said received primary data signal independently of the derivation of the LPC coefficients used during said using step.

8. A method in accordance with claim 1 wherein a plurality of auxiliary information signals are transported on said primary data signal, said method comprising the further steps of:

modulating a plurality of pseudorandom noise carriers by said plurality of auxiliary information signals to provide a plurality of spread spectrum signals;

providing said plurality of pseudorandom noise carriers with a spectral shape to simulate the spectral shape of said primary data signal; and

combining the plurality of pseudorandom noise carriers with said primary data signal to produce an output signal carrying said auxiliary information signals as noise in said primary data signal.

9. A method in accordance with claim 8 wherein each of said plurality of pseudorandom noise carriers is individually spectrally shaped prior to its combination with said primary data signal.

10. A method in accordance with claim 8 wherein said plurality of pseudorandom noise carriers are spectrally shaped as a group prior to their combination with said primary data signal.

11. A method in accordance with claim 8 wherein:

at least one of said plurality of pseudorandom noise carriers is individually spectrally shaped prior to its combination with said primary data signal, and

at least two other of said plurality of pseudorandom noise carriers are spectrally shaped as a group prior to their combination with said primary data signal.

12. A method in accordance with claim 8 wherein:

the plurality of pseudorandom noise carriers are combined with said primary data signal such that at least one of said plurality of pseudorandom noise carriers is combined with said primary data signal after said primary data signal has already been combined with at least one other of said plurality of pseudorandom noise carriers.

13. A method in accordance with claim 8 comprising the further step of providing at least one of a modulated or unmodulated pseudorandom noise carrier as a pilot signal for use in synchronizing a receiver function.

14. A method in accordance with claim 8, comprising the further step of:

adjusting the gain of at least one of said plurality of pseudorandom noise carriers prior to its combination with said primary data signal.

15. A method in accordance with claim 14, wherein:

a group of said plurality of pseudorandom noise carriers has an adjusted power so that the group is provided at a desired level in said primary data signal.

16. A method in accordance with claim 8, wherein:

a gain of at least a first one of the plurality of pseudorandom noise carriers is determined; and

a gain of at least a second one of the plurality of pseudorandom noise carriers is adjusted in response to the gain determined for the at least one first carrier.

17. A method in accordance with claim 16, wherein:

a group of at least said first and second pseudorandom noise carriers has an adjusted power so that the group is provided at a desired level in said primary data signal.

18. A method in accordance with claim 8 wherein at least two of said plurality of pseudorandom noise carriers are provided at different data rates.

19. A method for recovering said auxiliary information from the output signal of claim 8 comprising the steps of:

evaluating said output signal to approximate its spectral shape;

processing the output signal based on the approximate spectral shape determined therefor, to whiten said noise; and

demodulating a desired spread spectrum signal after said noise has been whitened to recover the auxiliary information carried thereby.

20. A method in accordance with claim 19 wherein a plurality of said spread spectrum signals are demodulated substantially simultaneously from said output signal.

21. A method in accordance with claim 1 wherein said pseudorandom noise carrier is generated cryptographically to provide secure communication of said auxiliary information to a receiver.

22. A method for transporting a plurality of auxiliary information signals in a primary data signal, comprising the steps of:

modulating each of a plurality of pseudorandom noise carriers by at least one different one of said auxiliary information signals to provide a plurality of spread spectrum signals carrying auxiliary information on carrier portions thereof;

evaluating said primary data signal using subband analysis to estimate its spectral shape;

subband filtering said plurality of spread spectrum signals in response to said subband analysis to provide the carrier portions of said spread spectrum signals with a spectral shape which simulates the spectral shape of said primary data signal; and

combining the carrier portions with said primary data signal to produce an output signal carrying said auxiliary information signals as noise in said primary data signal.

23. A method in accordance with claim 22 wherein said evaluating and subband filtering steps comprise fast Fourier transform (FFT) analysis and FFT filtering, respectively.

24. A method in accordance with claim 22 wherein each of said carrier portions is individually spectrally shaped prior to its combination with said primary data signal.

25. A method in accordance with claim 22 wherein said carrier portions are spectrally shaped as a group prior to their combination with said primary data signal.

26. A method in accordance with claim 22 wherein:

at least one of said carrier portions is individually spectrally shaped prior to its combination with said primary data signal, and

at least two other of said carrier portions are spectrally shaped as a group prior to their combination with said primary data signal.

27. A method in accordance with claim 22 wherein:

at least one of said carrier portions is combined with said primary data signal after said primary data signal has already been combined with at least one other of said carrier portions.

28. A method in accordance with claim 22 comprising the further step of providing at least one of a modulated or unmodulated pseudorandom noise carrier as a pilot signal for use in synchronizing a receiver function.

29. A method in accordance with claim 22, wherein:

at least one of said carrier portions has an adjusted power.

30. A method in accordance with claim 29, wherein:

a group of said carrier portions has an adjusted power so that said group is provided at a desired level in said primary data signal.

31. A method in accordance with claim 22, wherein:

a gain of at least a first one of the carrier portions is determined; and

a gain of at least a second one of the carrier portions is adjusted in response to the gain determined for the at least one first carrier portion.

32. A method in accordance with claim 31, wherein:

a group of at least said first and second carrier portions has an adjusted power so that the group is provided at a desired level in said primary data signal.

33. A method in accordance with claim 22 wherein at least two of said carrier portions are provided at different data rates.

34. A method for recovering said auxiliary information from the output signal of claim 22 comprising the steps of:

evaluating said output signal to approximate its spectral shape;

processing the output signal, based on the approximate spectral shape determined therefor, to whiten said noise; and

demodulating a desired spread spectrum signal after said noise has been whitened to recover the auxiliary information carried thereby.

35. A method in accordance with claim 34 wherein a plurality of said spread spectrum signals are demodulated substantially simultaneously from said output signal.

36. Apparatus for transporting auxiliary information in a primary data signal for communication to a receiver, comprising:

means for converting a data stream of said auxiliary information into a spread spectrum signal carrying said information;

means for evaluating said primary data signal using time domain modeling to obtain an approximation of its spectral shape; and

a time domain synthesizer responsive to said evaluating means for providing a carrier portion of said spread spectrum signal with a spectral shape which simulates the spectral shape of said primary data signal, thereby producing a noise signal containing said auxiliary information to be carried in said primary data signal.

37. Apparatus in accordance with claim 36 further comprising:

means for combining said noise signal with said primary data signal to produce an output signal carrying said auxiliary information as noise in said primary data signal.

38. Apparatus in accordance with claim 37, further comprising:

means for providing said noise signal with an adjusted power so that said noise signal is provided at a desired level in said primary data signal.

39. Apparatus in accordance with claim 36 wherein:

said evaluating means comprise a linear predictive coding (LPC) processor coupled to receive said primary data signal and generate LPC coefficients therefrom; and

said time domain synthesizer comprises an LPC filter responsive to said LPC coefficients.

40. Apparatus for recovering said auxiliary information from a received primary data signal carrying the noise signal provided by the apparatus of claim 36, comprising:

means for evaluating said received primary data signal using time domain modeling to approximate its spectral shape;

a time domain processor for processing the received primary data signal, based on the spectral shape determined therefor, to whiten the noise signal contained therein; and

means for demodulating the whitened noise signal to recover said data stream of said auxiliary information.

41. Apparatus in accordance with claim 40, wherein:

said primary data signal is a stereo frequency-modulated signal which is subsequently modulated at a carrier frequency for transmission at said carrier frequency; and

said noise signal is carried in at least one of;

(a) said stereo frequency-modulated signal prior to said modulation at said carrier frequency, and (b) said stereo frequency-modulated signal subsequent to said modulation at said carrier frequency.

42. Apparatus in accordance with claim 40 wherein:

said means for evaluating said primary data signal comprise a first linear predictive coding (LPC) processor coupled to receive said primary data signal and generate first LPC coefficients therefrom;

said time domain synthesizer comprises a first LPC filter responsive to said first LPC coefficients;

said means for evaluating said received primary data signal comprise a second LPC processor for generating second LPC coefficients from the received primary data signal; and

said time domain processor comprises a second LPC filter responsive to said second LPC coefficients.

43. Apparatus in accordance with claim 42 further comprising:

means for providing said noise signal with an adjusted power to render said noise signal at a desired level in said primary data signal.

44. Apparatus for transporting a plurality of auxiliary information streams in a primary data signal, comprising:

means for converting said plurality of auxiliary information streams into spread spectrum signals;

means for evaluating said primary data signal to obtain an approximation of its spectral shape; and

means responsive to said evaluating means for providing carrier portions of said spread spectrum signals with a spectral shape which simulates the spectral shape of said primary data signal;

wherein a combination of said spread spectrum signals is used to provide noise simulating the spectral shape of said primary data signal for carrying said auxiliary information in said primary data signal.

45. Apparatus in accordance with claim 44 further comprising:

means for providing at least one of said carrier portions with an adjusted gain.

46. A method in accordance with claim 45, further comprising:

means for providing a group of said carrier portions with an adjusted power so that said group is provided at a desired level in said primary data signal.

47. Apparatus in accordance with claim 44, further comprising:

means for determining a gain of at least one first carrier to be carried in said primary data signal; and

means for providing at least one second carrier to be carried in said primary data signal with an adjusted gain which is responsive to the gain determined for said at least one first carrier.

48. Apparatus in accordance with claim 47 further comprising:

means for providing a group of at least said first and second carriers with an adjusted power so that the group is provided at a desired level in said primary data signal.

49. Apparatus in accordance with claim 44 wherein:

said means for evaluating said primary data signal use time domain modeling to obtain said approximation of the primary data signal spectral shape; and

said means responsive to said evaluating means comprise a time domain synthesizer.

50. Apparatus in accordance with claim 44 wherein:

said means for evaluating said primary data signal use subband analysis to obtain said approximation of the primary data signal spectral shape; and

said means responsive to said evaluating means comprise at least one subband filter.

51. Apparatus in accordance with claim 50 wherein said subband analyzer and subband filter comprise a fast Fourier transform (FFT) analyzer and filter, respectively.

52. Apparatus in accordance with claim 44 further comprising:

means for providing said noise with an adjusted power to render it at a desired level in said primary data signal.

53. Apparatus in accordance with claim 44 wherein:

said plurality of auxiliary information streams have different data rates; and

said means for converting said auxiliary information streams into spread spectrum signals comprise pseudorandom sequence generators providing different output rates for the different information streams.

54. Apparatus in accordance with claim 44 wherein:

said means for converting said auxiliary information streams into spread spectrum signals comprise pseudorandom sequence generators providing orthogonal pseudorandom sequences for the different information streams.

55. A decoder for recovering auxiliary information carried by a spread spectrum signal that is transported as noise in a primary data signal, said spread spectrum signal including a carrier having a spectral shape which simulates the spectral shape of information contained in said primary data signal, said decoder comprising:

means for evaluating said primary data signal using time domain modeling to approximate its spectral shape;

a time domain processor for processing the primary data signal, based on the spectral shape determined therefor, to whiten the spread spectrum carrier contained therein; and

means for demodulating the whitened spread spectrum carrier to recover said auxiliary information.

56. A decoder in accordance with claim 55 wherein:

said evaluating means comprise a linear predictive coding (LPC) processor coupled to receive said primary data signal and generate LPC coefficients therefrom; and

said time domain processor comprises an LPC filter responsive to said LPC coefficients.

57. A decoder in accordance with claim 55 wherein:

a plurality of auxiliary information signals are carried on respective carriers of said spread spectrum signal, all of said carriers having a spectral shape which simulates the spectral shape of said primary data signal information; and

said demodulator means include means for selecting at least one desired carrier for demodulation to enable the recovery of at least one corresponding auxiliary information signal.

58. A decoder in accordance with claim 56 wherein:

a plurality of auxiliary information signals are carried on respective carriers of said spread spectrum signal, all of said carriers having a spectral shape which simulates the spectral shape of said primary data signal information; and

said demodulator means include means for substantially simultaneously demodulating a plurality of said carriers to enable the substantially simultaneous recovery of said auxiliary information signals.

59. A decoder for recovering a plurality of auxiliary information streams carried by a spread spectrum signal that is transported as noise in a primary data signal, said spread spectrum signal including a plurality of carriers having a spectral shape which simulates the spectral shape of information contained in said primary data signal, said decoder comprising:

means for evaluating said primary data signal to determine its approximate spectral shape;

means for processing the primary data signal, based on the spectral shape determined therefor, to whiten the spread spectrum carriers contained therein; and

means for demodulating the whitened spread spectrum carriers to recover said auxiliary information streams.

60. A decoder in accordance with claim 59 wherein:

said evaluating means comprise a linear predictive coding (LPC) processor coupled to receive said primary data signal and generate LPC coefficients therefrom; and

said processing means comprise an LPC filter responsive to said LPC coefficients.

61. A decoder for recovering auxiliary information carried by a spread spectrum signal transported as noise in a primary data signal, comprising:

means for whitening a spectrum of said primary data signal, said whitening means creating intersymbol interference in said spread spectrum signal; and

a rake receiver for receiving and demodulating said primary data signal from said whitening means;

wherein;

said rake receiver has a plurality of fingers for processing different multipaths of said spread spectrum signal when demodulating the received primary data signal, thereby recovering said spread spectrum signal with reduced intersymbol interference in order to obtain said auxiliary information therefrom;

said spread spectrum signal is provided by modulating a pseudorandom noise carrier by said auxiliary information; and

a carrier portion of said spread spectrum signal has a spectral shape that approximates a spectral shape of said primary data signal.

62. A decoder in accordance with claim 61 wherein said whitening means comprise:

a linear predictive coding (LPC) processor coupled to receive said primary data signal and generate LPC coefficients therefrom, and

an LPC filter of order N for receiving said primary data signal and responsive to said LPC coefficients for whitening said spectrum of said primary data signal;

said rake receiver comprising N fingers, where N is approximately equal to the order of said LPC filter.

63. A decoder in accordance with claim 61 wherein said whitening means comprise:

a subband analyzer coupled to receive and estimate the spectrum of said primary data signal; and

a subband filter responsive to the spectrum estimated by said subband analyzer for filtering said primary data signal to whiten the spectrum thereof.

64. A decoder in accordance with claim 61 wherein each of said fingers has an associated weight, said rake receiver further comprising:

means for individually adjusting the weights of said rake receiver fingers.

65. A decoder in accordance with claim 64 wherein the weights of said rake receiver fingers are dynamically adjustable.

66. A decoder in accordance with claim 65 wherein said weights are dynamically adjustable in response to coefficients generated by said whitening means.

67. A data signal embodied in a carrier wave, comprising:

a primary data signal portion having an associated spectral shape; and

a noise signal portion carried in said primary data signal;

wherein;

said noise signal portion comprises a spread spectrum signal carrier that carries auxiliary information;

said spread spectrum signal carrier has an associated spectral shape which approximates said spectral shape of said primary data signal; and

said spread spectrum signal carrier is provided with the associated spectral shape thereof by filtering said spread spectrum signal carrier with a time domain synthesis filter that is responsive to a time domain model of said spectral shape of said primary data signal.

68. The data signal of claim 67, wherein:

said spread spectrum signal carrier is provided by modulating a pseudorandom noise carrier by said auxiliary information.

69. The data signal of claim 67, wherein:

said noise signal portion comprises a plurality of spread spectrum signal carriers that carry corresponding auxiliary information signals; and

said plurality of spread spectrum signal carriers are provided by modulating each of a corresponding plurality of pseudorandom noise carriers by a corresponding one of said auxiliary information signals.