Digital watermark screening and detecting strategies

• US 6,516,079 B1
• Filed: 03/15/2000
• Issued: 02/04/2003
• Est. Priority Date: 02/14/2000
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Sharma, Ravi K., Rhoads, Geoffrey B.
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): NAKHJAVAN, SHERVIN K
• Application Number:
  US09/526,982
• Time in Patent Office: 1,056 Days
• Field of Search: 382/100, 382/190, 382/195, 382/206, 382/209, 382/219, 382/220, 382/221, 382/224, 382/229, 382/232, 382/233, 382/235, 382/276, 382/278, 382/280, 382/286, 382/287, 713/155, 713/160, 713/161, 713/162, 713/168, 713/176, 713/179, 713/180, 713/181, 713/187, 713/189, 380/200, 380/250, 380/252, 380/253, 380/254, 380/277, 380/56, 340/825.34, 348/465, 348/604
• US Class Current: 382/100
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32288 Multiple embedding, e.g. cocktail embedding, or redundant embedding, e.g. repeating the additional information at a plurality of locations in the image
• CPC Class Codes: H04N 1/32352 Controlling detectability or arrangements to facilitate detection or retrieval of the embedded information, e.g. using markers for decoding, detection or retrieval operations H04N1/32149 and subgroups take precedence
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/645 by grouping of coefficients into blocks after the transform
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• CPC Class Codes: H04N 21/23892 involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/44008 involving operations for analysing video streams, e.g. detecting features or characteristics in the video stream arrangements characterised by components specially adapted for monitoring, identification or recognition of video in broadcast systems H04H60/59
• CPC Class Codes: H04N 21/4627 Rights management associated to the content security in data switching network management H04L41/28; security management or policies for network security H04L63/20; access security in wireless networks H04W12/08
• CPC Class Codes: H04N 21/8358 involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3284 : for error correction
• CPC Class Codes: H04N 7/163 : by receiver means only

Abstract

To enhance decoding of signals suspected of containing a watermark, a suspect signal is screened to compute detection values evincing presence and strength of a watermark. Screening strategies control detector actions, such as rejecting un-marked signals and improving synchronization of watermarks in suspect signals.

Claims

1. A method of using detection values computed from a signal suspected of being watermarked to control watermark detection, the method comprising:

computing detection values for two or more candidate watermark signals in a suspect signal, where each detection value corresponds to a metric indicating likelihood of a watermark signal in the suspect signal, the watermark signal being detected comprises a set of attributes embedded at locations within the suspect signal, and catch detection value is a measure of the set of attributes;

computing a relative detection value based on an analysis of two or more of the detection values relative to each other, and

controlling detector action based on the relative detection value.

2. The method of claim 1:

including computing an absolute detection value for at least one candidate watermark signal in the suspect signal; and

controlling detector action based at last in part on the absolute and relative detection values.

3. The method of claim 2 wherein the detector action comprises screening unmarked signals from further detection action.

4. The method of claim 1 including determining whether to reject a suspect signal as being un-marked by comparing the relative detection value to a limit.

5. The method of claim 1 including determining whether to reject at least a portion of the suspect signal as being un-marked by two or more screening stages, where a first screening stage tests a set of candidate watermark signals;

and a subsequent screening stage tests candidate watermark signals that remain after the first screening stage.

6. The method of claim 1 including selecting additional candidate watermark signals in the suspect signal based on the detection values;

and

computing detection values for the additional candidates in an attempt to find candidates that evince a stronger watermark signal.

7. The method of claim 6 wherein selecting additional candidate watermark signals comprises refining orientation parameters associated with the candidate watermark signals.

8. The method of claim 1 wherein the detection values comprise measures of correlation between a calibration signal and at least portions of the suspect signal.

9. The method of claim 1 wherein the detection values comprise a measure of similarity between an expected calibration signal and a calibration signal decoded from at least a portion of the suspect signal.

10. The method of claim 1 wherein the relative detection value is used as an indicator of strength of a watermark in the suspect signal.

11. The method of claim 1 wherein the relative detection value is used to control use, copying or recording of the suspect signal.

12. The method of claim 1 wherein the relative detection value is used to determine whether the suspect signal has been tampered with.

13. A computer readable medium on which is stored software for performing the method of claim 1.

14. The method of claim 1 wherein the detection values comprise measures of correlation.

15. The method of claim 14 wherein the relative detection value comprises a comparison of a top correlation measure with one or more lesser correlation measures.

16. A method of using detection values computed from a signal suspected of being watermarked to control watermark detection, the method comprising:

computing detection values for two or more candidate watermark signals in a suspect signal, where each detection value corresponds to a metric indicating likelihood of a watermark signal in the suspect signal, the watermark signal being detected comprises a set of attributes embedded at locations within the suspect signal;

computing a relative detection value based on an analysis of two or more of the detection values relative to each other, and

controlling detector action based on the relative detection value;

where the candidate watermark signals have corresponding orientation parameters describing orientations of the candidate watermark signals in the suspect signal.

17. The method of claim 16 wherein the candidate watermark signals are each represented by one or more orientation parameters that approximate a spatial or temporal transform that at least a portion of the suspect signal has undergone subsequent to being encoded with a watermark.

18. A method of detecting a watermark having a set of attributes embedded at locations within a suspect signal, the method comprising:

computing detection values for two or more watermark signal candidates in the suspect signal;

evaluating a first detection metric based on the detection values;

evaluating a second detection metric based on the detection values; and

controlling further detector actions based on the first and second detection metrics;

wherein at least one of the metrics uses criteria indicating whether a valid watermark signal is present that adapts to the suspect signal according to detection values computed from the suspect signal; and

wherein the detection values are each computed as a measure of the set of attributes of the watermark.

19. The method of claim 18 wherein the detection metrics comprise first and second screening stages and the second screening stage screens candidate watermark signals that remain after the first screening stage.

20. The method of claim 19 wherein each stage screens candidate watermark signals in a suspect signal deemed to be un-marked.

21. The method of claim 18 wherein each of the detection stages perform one or more of the following:

comparing a top detection value to a limit, and

comparing a top detection value to a one or more lesser detection values or combination of lesser detection values.

22. The method of claim 18 wherein the detection values are computed for candidate watermark signals and the first and second detection metrics are used as an indicator of strength of a watermark in the suspect signal.

23. The method of claim 22 wherein the strength of the watermark is used to determine whether the suspect signal has been transformed.

24. The method of claim 22 wherein the strength of the watermark is used to control use, recording or copying of the suspect signal.

25. The method of claim 18 wherein the detection values are computed for candidate watermark signals and the first and second detection metrics are used to control use, recording or copying of the suspect signal.

26. A computer readable medium on which is stored software for performing the method of claim 18.

27. The method of claim 18 wherein the detection values comprise measures of correlation and at least one of the detection metrics comprises an evaluation of relative correlation measures for different candidate watermark signals.

28. The method of claim 27 wherein the evaluation includes comparing a top correlation measure with one or more lesser correlation measures.

29. A method of watermark detection in a signal suspected of being watermarked comprising:

computing two or more features of a suspect signal from different stages of watermark detection; and

combining information from the two or more features to control watermark detector action;

wherein at least one feature provides a measure of watermark signal validity of a watermark signal candidate relative to other watermark signal candidates; and

the at least one feature comprises a comparison of a top detection value of a watermark signal candidate with lesser detection values of other watermark signal candidates.

30. The method of claim 29 wherein the detector action is screening an unmarked signal.

31. The method of claim 29 wherein the two or more features comprise different measures of correlation.

32. The method of claim 29 wherein the two or more features comprise independent detection values.

33. The method of claim 29 wherein the detector action is a subsequent detection stage.

34. A computer readable medium on which is stored software for performing the method of claim 29.

35. The method of claim 29 wherein the detection values comprise correlation values.

36. The method of claim 29 wherein a watermark being detected comprises a set of attributes embedded at locations within the signal suspected of being watermarked.

37. The method of claim 36 wherein the detection values comprise correlation values.