Embedding data in material

• US 7,088,843 B2
• Filed: 12/06/2001
• Issued: 08/08/2006
• Est. Priority Date: 12/07/2000
• Status: Expired due to Fees

• Current Assignee: Sony United Kingdom Limited (Sony Group Corp.)
• Original Assignee: Sony United Kingdom Limited (Sony Group Corp.)
• Inventors: Pelly, Jason Charles
• Primary Examiner(s): Ahmed, Samir
• Assistant Examiner(s): BHATNAGAR, ANAND P
• Application Number:
  US10/006,294
• Publication Number:
  US 20020118859A1
• Time in Patent Office: 1,706 Days
• Field of Search: 382/100, 382/232, 713/176
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0081 whereby both original and watermarked images are required at decoder, e.g. destination-based, non-blind, non-oblivious
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• CPC Class Codes: G06T 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
• CPC Class Codes: G06T 2201/0203 whereby the image with embedded watermark is reverted to the original condition before embedding, e.g. lossless, distortion-free or invertible watermarking
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/3217 using wavelet transforms
• CPC Class Codes: H04N 1/32347 Reversible embedding, i.e. lossless, invertible, erasable, removable or distorsion-free embedding
• CPC Class Codes: H04N 2201/328 Processing of the additional information

Abstract

A method of embedding data in material comprises the steps of:

• • embedding data in original material to produce data embedded material;
  • removing the watermark from the data embedded material to produce recovered material;
  • comparing the original and recovered material to determine the differences and locations of differences therebetween; and
  • storing the said locations and corrections which correct the said differences.

A method of removing the data embedded in the material, comprises the steps of:

• • removing the data from the material to produce recovered material;
  • deriving the said corrections and locations from the said store; and
  • using the corrections to correct the recovered material at the said locations.

A method of embedding data in material, preferably comprises the steps of:

• • producing transform coefficients Ci representing a spatial frequency transform of the material, and
  • combining the coefficients Ci with the data bits Ri to produce a modified coefficient Ci′ where
    Ci′=Ci+αiRi
  • the method further comprising determining αi for each unmodified coefficient Ci as a function F{Cn}_i of a predetermined set {Cn}_i of transform coefficients Cn which set excludes the coefficient Ci.

Claims

1. A method of embedding data in material, the method comprising the steps of:

producing transform coefficients C_i representing a transform of the material, and

combining the coefficients C_i with data symbols R_i to produce modified coefficients C_i′

where

C_i′

=C_i+α

_iR_i

the method further comprising determining an adaptation strength α

_i for each unmodified coefficient C_i as a function F{C_n}_i of a predetermined set {C_n}_i of transform coefficients C_n which set excludes the coefficient C_i wherein the coefficients are serially ordered and the coefficients C_n are coefficients preceding coefficient C_i.

2. The method according to claim 1, wherein the coefficients the set {C_n}_i vary with i.

3. The method according to claim 1, wherein the number N_i of coefficients in the set {C_n}_i varies with i.

4. The method according to claim 1, wherein the coefficients of the set {C_n}_i have a predetermined positional relationship with the coefficient C_i to be modified.

5. The method according to claim 1, wherein the coefficients represent a spatial frequency transform of the material.

6. The method according to claim 1, wherein the coefficients represent a wavelet transform of the material.

7. The method according to claim 6, wherein the transform produces coefficients C_i in a plurality of bands.

8. The method according to claim 7, wherein the transform coefficients forming the set {C_n}_i are all in the same band.

9. The method according to claim 7, wherein the transform coefficients forming the set {C_n}_i are in a plurality of bands.

10. The method according to claim 1, wherein the said function F{C_n}_i is such that

$\alpha$

⁢

⁢

i = 1 N ⁢

⁢

i ·

∑

C n 2

for n=i-1 to i-N_i for N_i≠

0 and α

_i=k for N_i=0,

where N_i is the number of coefficients C_n in set i.

11. The method according to claim 1, wherein the said data symbols R_i are of a pseudo random symbol sequence having symbols P_i modulated by data W_j to be embedded.

12. The method according to claim 1, wherein the data is imperceptibly embedded in the other material.

13. The method according to claim 1, wherein the set {C_n}_i includes unmodified coefficients.

14. The method according to claim 1, wherein the set {C_n}_i consists of modified coefficients preceding C_i where the coefficients are serially ordered.

15. The method according to claim 1, wherein the set {C_n}_i comprises at least one modified coefficient and at least one unmodified coefficient.

16. A computer program product arranged to carry out the method of claim 1 when run on a computer.

17. The method according to claim 1, wherein the material is video material.

18. The method according to claim 1, wherein the material is audio material.

19. The method according to claim 1, wherein the material is audio/visual material.

20. An apparatus for embedding data in material, comprising

a transformer for producing transform coefficients C_i representing a transform of the material, and

a combiner for combining the coefficients C_i with data symbols R_i to produce modified coefficients C_i′

where

Ci′

=C_i+α

_iR_i,

the apparatus further comprising

a calculator for calculating an adaptation strength α

_i for each unmodified coefficient C_i as a function F{C_n}_i of a predetermined set {C_n}_i of transform coefficients C_n which set excludes the coefficient C_i, wherein the coefficients are serially ordered and the coefficients C_n are coefficients preceding coefficient C_i.

21. The apparatus according to claim 20, wherein the coefficients of the set {C_n}_i vary with i.

22. The apparatus according to claim 20, wherein the unmodified coefficients of the set {C_n}_i have a predetermined positional relationship with the coefficient C_i to be modified.

23. The apparatus according to claim 20, wherein the coefficients represent a spatial frequency transform of the material.

24. The apparatus according to claim 20, wherein the coefficients represent a wavelet transform of the material.

25. The apparatus according to claim 24, wherein the transformer produces coefficients C_i in a plurality of frequency bands.

26. The apparatus according to claim 25, wherein the transform coefficients forming the set {C_n}_i are all in the same band.

27. The apparatus according to claim 26, wherein the transform coefficients forming the set {C_n}_i are in a plurality of bands.

28. The apparatus according to claim 20, wherein the said function F{C_n}_i is such that

$\alpha$

⁢

⁢

i = 1 N i ·

∑

C n 2

where N_i is the number of coefficients C_n in set i.

29. The apparatus according to claim 20, wherein the data is imperceptibly embedded in the other material.

30. The apparatus according to claim 20, wherein the set {C_n} consists of unmodified coefficients.

31. The apparatus according to claim 20, wherein the set {C_n}_i includes unmodified coefficients.

32. The apparatus according to claim 20, wherein the set {C_n}_i comprises at least one modified coefficient and at least one unmodified coefficient.

33. An apparatus for removing data embedded in material, the apparatus comprising:

a processor for determining the values of the symbols R_i;

a calculator for calculating, for each modified coefficient C_i′

, the value of the said function F{C_n}_i of the corresponding set {C_n}_i of coefficients C_n to determine α

_i; and

a subtractor which, for each modified coefficient C_i′

, subtracts therefrom α

_i.R_i to restore the unmodified coefficient value C_i, which thereby becomes available for use as an unmodified coefficient of another set {C_n}_i of unmodified coefficients C_n for restoring another coefficient C_i′

, wherein the coefficients are serially ordered and the said set {C_n}_i consists of coefficients preceding coefficient C_i.

34. The apparatus according to claim 33, wherein the said set {C_n}_i consists of restored coefficients C_i and further comprising means for using a restored coefficient C_i as a coefficient of another set {C_n}_i+1 of coefficients for restoring another coefficient C_i+1.

35. The apparatus according to claim 34, wherein the said set {C_n}_i includes modified coefficients preceding coefficient C_i.

36. The apparatus according to claim 34, wherein the said set {C_n}_i comprises at least one modified coefficient and at least one restored coefficient, the coefficients preceding C′

_i.

37. The apparatus according to claim 33, further comprising means for determining the values of the data bits W_j embedded in the material, said means for determining comprising a correlator for correlating a reference pseudo random symbol sequence with the modified coefficients C_i′

, a decoder for decoding the correlations to determine the data W_j modulating the modulated sequence and a modulator for remodulating the reference sequence with the said data to restore R_i.

38. A method of removing data embedded in material, the method comprising:

determining the values of the data symbols R_i;

calculating, for each modified coefficient C_i′

, the value of the said function;

F{C_n}_i of the corresponding set {C_n}_i of coefficients C_n to determine α

_i; and

for each modified coefficient C_i′

, subtracting therefrom α

_i.R_i to restore the unmodified coefficient value C_i, wherein the coefficients are serially ordered and the said set {C_n}_i consists of modified coefficients preceding coefficient C_i.

39. The method according to claim 38, wherein the said set {C_n}_i includes restored coefficients C_i, the method further comprising a step of using a restored coefficient C_i as a coefficient of another set {C_n}_j of coefficients for restoring another coefficient C_j.

40. The method according to claim 38, wherein the said set {C_n}_i comprises at least one modified coefficient and at least one restored coefficient, the coefficients preceding C′

_i.

41. The method according to claim 38, further comprising the step of determining the values of the data bits W_j embedded in material by correlating a reference pseudo random symbol sequence with the modified coefficients C_i′

and decoding the correlation values to determine the data W_j modulating the pseudo random sequence and remodulating the reference sequence with the said data to restore R_i.

42. A computer program product arranged to carry out the method of claim 38 when run on a computer.