Methods and apparatus for enhancing the robustness of watermark extraction from digital host content

1. A method for watermark extraction from digital host content, comprising:

receiving a digital host content at a reception device; and

extracting embedded watermarks from the host content, using an extraction device, the extracting comprising:

decoding individual symbols of an embedded watermark in accordance with at least one watermark detection algorithm, wherein the decoding produces a correlation value, within a range of correlation values, for each individual symbol;

assigning a discrete symbol value to each decoded symbol;

associating a likelihood measure with each decoded symbol in accordance with the corresponding correlation value; and

determining whether or not the decoded symbols constitute a valid watermark in accordance with a cumulative assessment of the discrete symbol values and the likelihood measures.

2. The method of claim 1 , wherein the likelihood measure comprises a probability value.

3. The method of claim 1 , wherein the determining comprises:

arranging the decoded watermark symbols in a pre-defined order to form a decoded watermark packet;

comparing the decoded watermark packet, one symbol at a time, to a predefined template of watermark symbols;

producing an accumulated error value by:

adding a first probability value for each symbol of the decoded watermark packet that correctly matches the corresponding symbol within the predefined template, and

adding a second probability value for each symbol of the decoded watermark packet that does not match the corresponding symbol within the predefined template; and

comparing the accumulated error value to a predetermined reference value.

4. The method of claim 1 , wherein the likelihood measures are obtained in accordance with a set of pre-defined threshold values.

5. The method of claim 4 , wherein the likelihood measures are generated in accordance with a distance between the correlation values and the threshold values.

6. The method of claim 1 , wherein the detection algorithm comprises at least one of spread spectrum, autocorrelation modulation, peak amplitude modulation, or replica modulation techniques.

7. The method of claim 1 , wherein subsequent to the receiving of the digital host content, at least one boundary of the embedded watermarks is estimated by detecting a presence of a synchronization pattern embedded in the digital host content.

8. The method of claim 7 , wherein the detecting of the synchronization pattern comprises:

decoding individual bits of an embedded pattern in accordance with the at least one watermark detection algorithm, wherein decoding the individual bits produces a correlation value, within a range of correlation values, for each individual bit of the embedded pattern;

assigning a binary value to each decoded bit of the embedded pattern;

associating a likelihood measure with each binary value in accordance with the corresponding correlation value; and

determining a presence of the synchronization pattern in accordance with a cumulative assessment of the binary values and the likelihood measures associated with the binary values.

9. An apparatus, comprising:

a receiver configured to receive a digital host content; and

an extractor configured to extract embedded watermarks from the digital host content, the extractor configured to:

decode individual symbols of an embedded watermark in accordance with at least one watermark detection algorithm to produce a correlation value, within a range of correlation values, for each individual symbol;

assign a discrete symbol value to each decoded symbol;

associate a likelihood with each decoded symbol in accordance with the corresponding correlation value; and

determine whether or not the decoded symbols constitute a valid watermark in accordance with a cumulative assessment of the discrete symbol values and the likelihood measures.

10. The apparatus of claim 9 , wherein the extractor is configured to generate likelihood measures that comprise probability values.

11. The apparatus of claim 9 , wherein the extractor is configured to determine whether or not the decoded symbols constitute a valid watermark by:

arranging the decoded watermark symbols in a pre-defined order to form a decoded watermark packet;

comparing the decoded watermark packet, one symbol at a time, to a predefined template of watermark symbols;

producing an accumulated error value by:

adding a first probability value for each symbol of the decoded watermark packet that correctly matches the corresponding symbol within the predefined template, and

adding a second probability value for each symbol of the decoded watermark packet that does not match the corresponding symbol within the predefined template; and

comparing the accumulated error value to a predetermined reference value.

12. The apparatus of claim 9 , wherein the extractor is configured to generate the likelihood measures in accordance with a set of pre-defined threshold values.

13. The apparatus of claim 12 , wherein the extractor is configured to generate the likelihood measures in accordance with a distance between the correlation values and the threshold values.

14. The apparatus of claim 9 , wherein the extractor is configured to decode individual symbols of the embedded watermark in accordance with at least one spread spectrum, autocorrelation modulation, peak amplitude modulation, or replica modulation techniques.

15. The apparatus of claim 9 , wherein the extractor is further configured to:

detect a presence of a synchronization pattern embedded in the digital host content; and

determine at least one boundary of the embedded watermarks in accordance to the detected synchronization pattern.

16. The apparatus of claim 15 , wherein the extractor is further configured to detect the synchronization pattern by:

decoding individual bits of an embedded pattern in accordance with the at least one watermark detection algorithm, wherein decoding the individual bits produces a correlation value, within a range of correlation values, for each individual bit of the embedded pattern;

assigning a binary value to each decoded bit of the embedded pattern;

associating a likelihood measure with each binary value in accordance with the corresponding correlation value; and

determining a presence of the synchronization pattern in accordance with a cumulative assessment of the binary values and the likelihood measures associated with the binary values.

17. A non-transitory computer readable medium with program code embodied thereupon, the program code configured to extract embedded watermarks from the digital host content by:

decoding individual symbols of an embedded watermark in accordance with at least one watermark detection algorithm, wherein the decoding produces a correlation value, within a range of correlation values, for each individual symbol;

assigning a discrete symbol value to each decoded symbol;

associating a likelihood measure with each decoded symbol in accordance with the corresponding correlation value; and

determining whether or not the decoded symbols constitute a valid watermark in accordance with a cumulative assessment of the discrete symbol values and the likelihood measures.

18. The non-transitory computer readable medium of claim 17 , wherein the likelihood measures comprise probability values.

19. The non-transitory computer readable medium of claim 17 , wherein the determining comprises:

arranging the decoded watermark symbols in a pre-defined order to form a decoded watermark packet;

comparing the decoded watermark packet, one symbol at a time, to a predefined template of watermark symbols;

producing an accumulated error value by:

adding a first probability value for each symbol of the decoded watermark packet that correctly matches the corresponding symbol within the predefined template, and

adding a second probability value for each symbol of the decoded watermark packet that does not match the corresponding symbol within the predefined template; and

comparing the accumulated error value to a predetermined reference value.

20. The non-transitory computer readable medium of claim 17 , wherein the likelihood measures are obtained in accordance with a set of pre-defined threshold values.

21. The non-transitory computer readable medium of claim 20 , wherein the likelihood measures are generated in accordance with a distance between the correlation values and threshold values.

22. The non-transitory computer readable medium of claim 17 , wherein the detection algorithm comprises at least one of spread spectrum, autocorrelation modulation, peak amplitude modulation, or replica modulation techniques.

23. The non-transitory computer readable medium of claim 17 , wherein subsequent to the receiving of the digital host content, at least one boundary of the embedded watermarks is estimated by detecting a presence of a synchronization pattern embedded in the digital host content.

24. The non-transitory computer readable medium of claim 23 , wherein the detecting of the synchronization pattern comprises:

decoding individual bits of an embedded pattern in accordance with the at least one watermark detection algorithm, wherein decoding the individual bits produces a correlation value, within a range of correlation values, for each individual bit of the embedded pattern;

assigning a binary value to each decoded bit of the embedded pattern;

associating a likelihood measure with each binary value in accordance with the corresponding correlation value; and

determining a presence of the synchronization pattern in accordance with a cumulative assessment of the binary values and the likelihood measures associated with the binary values.

25. A non-transitory computer-readable storage medium with a host content embodied thereupon, the host content comprising:

one or more watermarks that are imperceptibly embedded in the host content, wherein reception of the host content by a content handling device equipped with a watermark extractor triggers the watermark extractor to:

decode individual symbols of an embedded watermark in accordance with at least one watermark detection algorithm to produce a correlation value, within a range of correlation values, for each individual symbol;

assign a discrete symbol value to each decoded symbol;

associate a likelihood with each decoded symbol in accordance with the corresponding correlation value; and

determine whether or not the decoded symbols constitute a valid watermark in accordance with a cumulative assessment of the discrete symbol values and the likelihood measures.