Using classification techniques in digital watermarking

1. A method for reading a digital watermark in a media signal, the method comprising:

using a computing device programmed to perform the acts of:

assigning sets of media signal samples into classes;

computing statistical characteristics of the media samples for the classes; and

using the statistical characteristics to adapt a digital watermark decoding function used to detect or read a watermark in the media signal.

2. The method of claim 1 , wherein the media signal is an audio signal.

3. The method of claim 1 , wherein the media signal is an image signal.

4. The method of claim 3 , wherein the image signal samples are expressed in a frequency domain.

5. The method of claim 4 , wherein the image signal samples are spatial frequency coefficients.

6. The method of claim 1 , wherein the samples are in a spatial or temporal domain.

7. The method of claim 1 , wherein using the statistical characteristics comprises assigning a figure of merit to a sample indicating a likelihood that the sample includes a recoverable portion of a watermark signal; and using the figure of merit in a read operation.

8. The method of claim 7 , wherein assigning a figure of merit comprises assigning a weight to the sample indicating an extent to which the sample is likely to reflect valid watermark data.

9. The method of claim 1 , wherein using the statistical characteristics comprises assigning a figure of merit to a sample indicating a likelihood that the sample includes a recoverable portion of a watermark signal; and using the figure of merit in a watermark decoding operation.

10. The method of claim 9 , wherein assigning a figure of merit comprises assigning a weight to the sample indicating an extent to which the sample is likely to reflect valid watermark data.

11. A non-transitory computer readable medium on which is stored instructions, which if executed by a computing device, cause the computing device to perform operations comprising:

assigning sets of media signal samples into classes;

computing statistical characteristics of the media samples for the classes; and

using the statistical characteristics to adapt a digital watermark decoding function used to detect or read a watermark in the media signal.

12. A method for reading a digital watermark in a media signal, the method comprising:

using a computing device programmed to perform the acts of:

assigning transformed samples of the media signal into classes using characteristics computed from the samples to group the samples into the classes;

computing statistical characteristics of the samples in each of the classes to compute a statistical feature of each of the classes; and

using the statistical feature to compute a detection metric to decode a watermark from the samples.

13. The method of claim 12 , wherein the characteristics further comprise signal activity of the samples, and the signal activity of the samples is evaluated and the samples are assigned to the classes based on signal activity.

14. A non-transitory computer readable medium on which is stored instructions, which if executed by a computing device, cause the computing device to perform operations comprising:

assigning transformed samples of the media signal into classes using characteristics computed from the samples to group the samples into the classes;

computing statistical characteristics of the samples in each of the classes to compute a statistical feature of each of the classes; and

using the statistical feature to compute a detection metric to decode a watermark from the samples.

15. A method for reading a digital watermark in a watermarked signal, the method comprising:

using a computing device programmed to perform the acts of:

assigning samples of the watermarked signal into classes using characteristics computed from the samples to group the samples into the classes;

computing a statistical analysis of the samples in each of the classes; and

using the statistical analysis to compute a decoding function for decoding a watermark from the watermarked signal.

16. The method of claim 15 , wherein sets of samples are assigned to classes based on a signal characteristic of the samples in the sets.

17. The method of claim 16 , wherein the signal characteristic is a measure of signal energy.

18. A non-transitory computer readable medium on which is stored instructions, which if executed by a computing device, cause the computing device to perform operations comprising:

assigning samples of the watermarked signal into classes using characteristics computed from the samples to group the samples into the classes;

computing a statistical analysis of the samples in each of the classes; and

using the statistical analysis to compute a decoding function for decoding a watermark from the watermarked signal.

19. A method for estimating a watermark signal from a media signal suspected of containing the watermark signal, the method comprising:

using a computing device programmed to perform the acts of:

assigning samples of the suspect signal into classes based on a signal characteristic of the samples;

calculating statistical characteristics of the classes; and

estimating the watermark signal based on the suspect signal, the statistical characteristics of the classes, and a characteristic of the watermark signal.

20. A non-transitory computer readable medium on which is stored instructions, which if executed by a computing device, cause the computing device to perform operations comprising:

assigning samples of the suspect signal into classes based on a signal characteristic of the samples;

calculating statistical characteristics of the classes; and

estimating the watermark signal based on the suspect signal, the statistical characteristics of the classes, and a characteristic of the watermark signal.