MODIFYING A CODED BITSTREAM

• US 20100027684A1
• Filed: 11/02/2007
• Published: 02/04/2010
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: ContentArmor
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Divorra Escoda, Oscar, Yin, Peng, Bloom, Jeffrey Adam, Zou, Dekun
• Granted Patent: US 8,358,703 B2
• Time in Patent Office: Days
• US Class Current: 375/240.260
• CPC Class Codes: G06T 1/0035 Output size adaptive watermarking
• CPC Class Codes: G06T 2201/0053 Embedding of the watermark in the coding stream, possibly without decoding; Embedding of the watermark in the compressed domain
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Implementations may relate to various aspects of modifying, or using, a coded bitstream, or to recovering water-marking information from data. In one implementation, a coded bitstream is modified to allow for the application of a watermark to the coded bitstream without changing the coding of any other syntax elements in the bitstream. This is performed by identifying conditions necessary to change a coded syntax element without disrupting the interpretation of subsequent coded elements. The coded syntax element is replaced with another coded value if the modified value generates the same decoding variables as the original value would have generated. Particular implementations focus on syntax elements coded using entropy coding, including, for example, Context-based Adaptive Binary Arithmetic Coding (CABAC). Regardless of the type of coding or watermarking, various implementations may provide for recovering watermarking information. Particular implementations recover watermarking information using detection data and feature information.

Claims

1. A method comprising:

accessing encoded data including at least a first portion and a second portion, wherein the second portion is decodable to produce a result that is based on the first portion as well as the second portion; and

determining a modified first portion such that the second portion is decodable to produce the result based on the second portion and the modified first portion.

2. The method of claim 1 further comprising replacing the first portion with the modified first portion.

3. The method of claim 1 wherein the modified first portion comprises a value having a bit length equal to that of the first portion.

4. The method of claim 1 wherein determining comprises determining a modified first portion that generates a CABAC state value that is the same as a state value for the first portion.

5. The method of claim 1 wherein decoding of the first portion produces a first result, decoding of the modified first portion produces a modified first result that is different from the first result.

6. The method of claim 1 wherein determining the modified first portion is based on providing a modified first result having a difference from the first result that is (1) imperceptible, from a viewer'"'"'s standpoint, and (2) detectable by a processing device.

7. The method of claim 6 wherein the modified first portion is suitable for watermarking the encoded data by replacing the first portion with the modified first portion.

8. The method of claim 1 wherein the result is based on the first portion by being based on a state produced from an encoding of the first portion.

9. The method of claim 1 wherein the first portion comprises a syntax element in a CABAC coded bitstream.

10. The method of claim 9 wherein determining further comprises:

determining all possible alternative replacement values for the syntax element; and

determining for each possible alternative replacement value, whether the replacement value generates the same state variable value for the syntax element; and

saving a list of alternative replacement values that do generate the same state variable value for the syntax element.

11. The method of claim 10 further comprising encoding the alternative replacement value before determining whether the replacement value generates the same state variable.

12. The method of claim 1 wherein the first portion comprises coded syntax elements, and wherein the modified first portion comprises a value having a bit length equal to that of the first portion, the modified first portion generating an L value in an CABAC encoder that is equal to the L value that would have been generated by the first portion.

13. The method of claim 1 wherein the second portion comprises more than one coded syntax element each having a corresponding state variable value, wherein the modified first portion maintains the state variable values for all decoding of all subsequent second portion syntax elements.

14. The method of claim 13 wherein the modified first portion does not affect the value of any other coded syntax element in the set of data.

15. The method of claim 1 wherein:

the encoded data comprises entropy encoded data,

the first portion comprises a syntax element, and

the modified first portion comprises a modification of the syntax element.

16. An apparatus comprising:

an accessing unit to access encoded data including at least two portions, wherein the second portion is decodable to produce a result, the result is based on the first portion as well as the second portion; and

a modification unit to determine a modified first portion such that the second portion is decodable to produce the result based on the second portion and the modified first portion.

17. An apparatus comprising:

means for accessing encoded data including at least two portions, wherein the second portion is decodable to produce a result, the result is based on the first portion as well as the second portion; and

means for determining a modified first portion such that the second portion is decodable to produce the result based on the second portion and the modified first portion.

18. An apparatus comprising a processor-readable medium including instructions stored on the processor-readable medium for performing at least the following:

accessing encoded data including at least two portions, wherein the second portion is decodable to produce a result, the result is based on the first portion as well as the second portion; and

determining a modified first portion such that the second portion is decodable to produce the result based on the second portion and the modified first portion.

19. An apparatus comprising a processor-readable medium including information stored on the processor-readable medium identifying a replacement value for a first portion of an encoded set of data, the encoded set of data also including a second portion, and decoding of the second portion being based on the second portion and on the first portion, wherein the replacement value has a property such that:

decoding of the second portion produces a particular decoded result if decoding is performed on the encoded set of data including the first portion, and

decoding of the second portion produces the particular decoded result if decoding is performed on the encoded set of data including the replacement value instead of the first portion.

20. A signal formatted to include information identifying a replacement value for a first portion of an encoded set of data, the encoded set of data also including a second portion, and decoding of the second portion being based on the second portion and on the first portion, wherein the replacement value has a property such that:

decoding of the second portion produces a particular decoded result if decoding is performed on the encoded set of data including the first portion, and

decoding of the second portion produces the particular decoded result if decoding is performed on the encoded set of data including the replacement value instead of the first portion.

21. The signal of claim 20 wherein the signal represents digital information.

22. The signal of claim 20 wherein the signal is a modulated electromagnetic wave.

23. A method comprising:

accessing a coded bitstream that includes at least a first portion and a second portion, the second portion being decodable to produce a result that is based on the first portion as well as the second portion; and

replacing the first portion with a replacement value to produce a modified coded bitstream for which a decoding of the second portion will still produce the result.

24. The method of claim 23 further comprising:

accessing an indicator of a location of the first portion; and

accessing a replacement value for the first portion, such that replacing the first portion with the replacement value results in a modified coded bitstream for which a decoding of the second portion will still produce the result.

25. The method of claim 23 further comprising accessing a piece of information, and wherein replacing the first portion comprises replacing the first portion based on the accessed piece of information.

26. The method of claim 25 wherein replacing the first portion is part of watermarking the coded bitstream, and the accessed piece of information comprises payload information.

27. The method of claim 26 wherein the value of the payload information dictates whether or not the first portion is to be replaced.

28. The method of claim 26 wherein the value of the payload information dictates which of multiple potential replacement values, including the replacement value, is to replace the first portion.

29. The method of claim 23 wherein accessing the encoded bitstream comprises accessing a bitstream encoded with an entropy code.

30. The method of claim 29 wherein the entropy code is an arithmetic code.

31. The method of claim 30 wherein the arithmetic code is CABAC.

32. The method of claim 31 wherein the replacement value and the first portion produce the same CABAC state values.

33. The method of claim 31 wherein the accessed coded bitstream comprises a CABAC coded bitstream, and the first portion comprising at least one coded syntax element in the CABAC coded bitstream.

34. The method of claim 24 wherein the accessed indicator comprises metadata.

35. The method of claim 23 wherein:

the second portion comprises more than one syntax element, and each of the more than one syntax elements has a corresponding state variable value that is produced during decoding of the modified coded bitstream, and

the replacement value for the first portion maintains the state variable values for each of the more than one syntax elements the same as if the first portion were used instead of the replacement value in the modified coded bitstream.

36. An apparatus comprising a processor-readable medium including instructions stored on the processor-readable medium for performing at least the following:

accessing a coded bitstream that includes at least two portions, the second portion being decodable to produce a result that is based on the first portion as well as the second portion; and

replacing the first portion with a replacement value to produce a modified coded bitstream for which a decoding of the second portion will still produce the result.

37. An apparatus comprising a processor-readable medium, the processor-readable medium having stored thereon encoded data including a modified first portion and a second portion, the modified first portion being a replacement of a first portion, wherein:

the second portion is decodable to produce a result that is based on the modified first portion as well as the second portion, and

the result is the same as if decoding of the second portion were performed based on the second portion and the first portion rather than the second portion and the modified first portion.

38. The apparatus of claim 37 wherein the modified first portion is at least part of a watermark included in the encoded data.

39. A signal formatted to include encoded data including a modified first portion and a second portion, the modified first portion being a replacement of a first portion, wherein:

the second portion is decodable to produce a result that is based on the modified first portion as well as the second portion, and

the result is the same as if decoding of the second portion were performed based on the second portion and the first portion rather than the second portion and the modified first portion.

40. The signal according to claim 39 wherein the modified first portion comprises at least one coded syntax element in a CABAC encoded bitstream.

41. The signal according to claim 40 wherein the modified first portion has a bit length equal to a bit length of the first portion prior to modification.

42. The signal according to claim 40 wherein the modified first portion produces the same state variables necessary for CABAC decoding of the second portion as the first portion would produce.

43. A method comprising:

accessing a modified set of data including a modified first portion and a second portion, the modified first portion resulting from a modification of a first portion, wherein the second portion is decodable to produce a result, and the result is based on the modified first portion as well as the second portion;

decoding the second portion to produce the result, wherein the result is the same as if decoding of the second portion were performed based on the second portion and the first portion rather than the second portion and the modified first portion; and

decoding the modified first portion.

44. The method of claim 43 wherein the modified first portion reflects a modification that was made based on a value of a piece of information, and the method further comprises determining the value of the piece of information based on the decoding of the modified first portion.

45. The method of claim 43 wherein the modified first portion is at least part of a watermark included in the modified set of data.

46. The method of claim 43 wherein the accessed modified set of data comprises a CABAC encoded bitstream and the first portion comprises at least one coded syntax element.

47. The method of claim 46 wherein the modified first portion comprises a modified syntax element, and the modified syntax element results in the same decoding variables for the CABAC encoded bitstream as does the first portion.

48. The method of claim 46 wherein the modified first portion comprises a modified syntax element having a bit length having equal to a bit length of the first portion, and the modified first portion results in an L value in an CABAC encoder that is equal to an L value that would have been generated by the first portion.

49. An apparatus comprising a processor-readable medium including instructions stored on the processor-readable medium for performing at least the following:

accessing a modified set of data including a modified first portion and a second portion, the modified first portion resulting from a modification of a first portion, wherein the second portion is decodable to produce a result, and the result is based on the modified first portion as well as the second portion;

decoding the second portion to produce the result, wherein the result is the same as if decoding of the second portion were performed based on the second portion and the first portion rather than the second portion and the modified first portion; and

decoding the modified first portion.