Efficient extraction of embedded watermarks in the presence of host content distortions

1. A method, comprising:

extracting a tentative watermark from an embedded host content, the tentative watermark representing a candidate watermark with an associated probability of false watermark detection that exceeds a desired probability of false watermark detection;

obtaining estimated distortion information indicative of a coarse value that approximates a particular distortion, or combination of distortions, present in the embedded host content using the extracted tentative watermark;

selecting one or more supplementary pre-distorted watermark templates that correspond to one or more distortion values in the vicinity of the coarse value, each of the supplementary pre-distorted watermark templates representing a watermark extracted from the host content when a specific distortion, or a specific combination distortions, is present in the host content; and

re-evaluating the extracted tentative watermark using the selected one or more supplementary pre-distorted watermark templates.

2. The method of claim 1 , wherein obtaining the estimated distortion information comprises:

selecting a plurality of coarse pre-distorted watermark templates that correspond to a range of distortion values of a particular distortion, or combination of distortions, with coarse granularity;

comparing the extracted tentative watermark to each of the plurality of coarse pre-distorted watermark templates; and

obtaining the estimated distortion information by identifying a first coarse pre-distorted watermark template that best matches the extracted tentative watermark.

3. The method of claim 2 , wherein the plurality of coarse pre-distorted watermark templates are selected at random from among a larger collection of pre-distorted watermark templates.

4. The method of claim 2 , wherein the plurality of coarse pre-distorted watermark templates are selected to correspond to one or more types of distortions that are likely to be present in the embedded host content.

5. The method of claim 1 , wherein the one or more supplementary pre-distorted watermark templates are selected to enable a search of distortion space in the vicinity of the coarse value with a fine granularity.

6. The method of claim 1 , wherein

the re-evaluating results in an improved estimate of the distortions present in the embedded host content.

7. The method of claim 6 , wherein the improved estimate is utilized to extract additional watermarks from the embedded host content.

8. The method of claim 1 , wherein the re-evaluating results in detection of a watermark with an improved probability of false watermark detection compared to probability of false watermark detection associated with the extracted tentative watermark.

9. The method of claim 1 , wherein the re-evaluating results in detection of a conclusive watermark with an associated probability of false watermark detection that is less than or equal to a desired probability of false watermark detection.

10. The method of claim 1 , wherein the re-evaluating comprises:

comparing the one or more supplementary pre-distorted watermark templates to the extracted tentative watermark;

producing an error count associated with each comparison, the error count representing how well the corresponding supplementary pre-distorted watermark template matches the extracted tentative watermark; and

selecting the supplementary pre-distorted watermark template that corresponds to smallest produced error count.

11. The method of claim 1 , wherein the one or more supplementary pre-distorted watermark templates are selected one-at-a-time in an iterative fashion.

12. A device, comprising

an extractor configured to extract a tentative watermark from an embedded host content, the tentative watermark representing a candidate watermark with an associated probability of false watermark detection that exceeds a desired probability of false watermark detection;

a distortion estimator configured to obtain estimated distortion information indicative of a coarse value that approximates a particular distortion, or combination of distortions, present in the embedded host content using the extracted tentative watermark, and to select one or more supplementary pre-distorted watermark templates that correspond to one or more distortion values in the vicinity of the coarse value, each of the supplementary pre-distorted watermark templates representing a watermark extracted from the host content when a specific distortion, or a specific combination distortions, is present in the host content; and

an evaluator configured to re-evaluate the extracted tentative watermark using the selected one or more supplementary pre-distorted watermark templates.

13. The device of claim 12 , wherein the distortion estimator is configured:

select a plurality of coarse pre-distorted watermark templates that correspond to a range of distortion values of a particular distortion, or combination of distortions, with coarse granularity;

compare the extracted tentative watermark to each of the plurality of coarse pre-distorted watermark templates; and

obtain the estimated distortion information by identifying a first coarse pre-distorted watermark template that best matches the extracted tentative watermark.

14. The device of claim 13 , wherein the distortion estimator is configured to select the plurality of coarse pre-distorted watermark templates at random from among a larger collection of pre-distorted watermark templates.

15. The device of claim 13 , wherein the distortion estimator is configured to select the plurality of coarse pre-distorted watermark templates to correspond to one or more types of distortions that are likely to be present in the embedded host content.

16. The device of claim 12 , wherein the distortion estimator is configured to select the one or more supplementary pre-distorted watermark templates to enable a search of distortion space in the vicinity of the coarse value with a fine granularity.

17. The device of claim 12 , wherein the re-evaluation of the extracted tentative watermark results in an improved estimate of the distortions present in the embedded host content.

18. The device of claim 17 , wherein extractor is configured to utilize the improved estimate to extract additional watermarks from the embedded host content.

19. The device of claim 12 , wherein re-evaluation of the extracted tentative watermark results in detection of a watermark with an improved probability of false watermark detection compared to probability of false watermark detection associated with the extracted tentative watermark.

20. The device of claim 12 , wherein re-evaluation of the extracted tentative watermark results in detection of a conclusive watermark with an associated probability of false watermark detection that is less than or equal to a desired probability of false watermark detection.

21. The device of claim 12 , wherein evaluator is configured to:

compare the one or more supplementary pre-distorted watermark templates to the extracted tentative watermark;

produce an error count associated with each comparison, the error count representing how well the corresponding supplementary pre-distorted watermark template matches the extracted tentative watermark; and

select the supplementary pre-distorted watermark template that corresponds to smallest produced error count.

22. The device of claim 12 , wherein the evaluator is configured to select the one or more supplementary pre-distorted watermark templates one-at-a-time in an iterative fashion.

23. A device, comprising:

a processor; and

a memory comprising processor executable code, the processor executable code, when executed by the processor, configures the device to:

extract a tentative watermark from an embedded host content, the tentative watermark representing a candidate watermark with an associated probability of false watermark detection that exceeds a desired probability of false watermark detection;

obtain estimated distortion information indicative of a coarse value that approximates a particular distortion, or combination of distortions, present in the embedded host content using the extracted tentative watermark;

select one or more supplementary pre-distorted watermark templates that correspond to one or more distortion values in the vicinity of the coarse value, each of the supplementary pre-distorted watermark templates representing a watermark extracted from the host content when a specific distortion, or a specific combination distortions, is present in the host content; and

re-evaluate the extracted tentative watermark using the selected one or more supplementary pre-distorted watermark templates.

24. A computer program product, embodied on a non-transitory computer readable medium, comprising:

program code for extracting a tentative watermark from an embedded host content, the tentative watermark representing a candidate watermark with an associated probability of false watermark detection that exceeds a desired probability of false watermark detection;

program code for obtaining estimated distortion information indicative of a coarse value that approximates a particular distortion, or combination of distortions, present in the embedded host content using the extracted tentative watermark;

program code for selecting one or more supplementary pre-distorted watermark templates that correspond to one or more distortion values in the vicinity of the coarse value, each of the supplementary pre-distorted watermark templates representing a watermark extracted from the host content when a specific distortion, or a specific combination distortions, is present in the host content; and

program code for re-evaluating the extracted tentative watermark using the selected one or more supplementary pre-distorted watermark templates.