Adaptive prediction filtering for digital watermarking

A method of digital watermark detection comprising:

• using a computer programmed as a digital watermark detector to perform the acts of:
• computing signal characteristics of a host digitally watermarked signal;
• analyzing the characteristics to determine an extent to which the signal characteristics correspond to characteristics of a digital watermark;
• adapting parameters of digital watermark prediction applied to the watermarked signal based on the extent to which the signal characteristics correspond to the characteristics of the digital watermark;
• wherein the digital watermark prediction predicts an estimate of an embedded digital watermark signal element based on comparison of a host signal value and one or more other related values, and the parameters correspond to a type of prediction filter that is selected based on the signal characteristics.

A method of digital watermark detection comprising:

• using a computer programmed as a digital watermark detector to perform the acts of:
• computing signal characteristics of a host digitally watermarked signal;
• analyzing the characteristics to determine an extent to which the signal characteristics correspond to characteristics of a digital watermark;
• adapting parameters of digital watermark prediction applied to the watermarked signal based on the extent to which the signal characteristics correspond to the characteristics of the digital watermark;
• wherein analyzing includes analyzing the signal characteristics of different portions of the host digitally watermarked signal, and wherein adapting parameters comprises selecting different prediction filters for the different portions of the host digitally watermarked signal, the prediction filters being selected so as to provide better correspondence between output of the selected filters and the characteristics of the digital watermark.

A method of decoding a digital watermark from a host signal, including the acts:

• using a computer programmed as a digital watermark decoder to perform the acts of:
• assessing characteristics of the host signal, and determining an initial filter function based on said characteristics;
• filtering the signal in accordance with the initial filter function;
• assessing the host signal relative to a digital watermark signal to determine a second filter function so that filter function is adapted based on an assessment of host signal characteristics relative to digital watermark signal characteristics;
• and
• filtering the host signal in accordance with the second filter function.

A method of decoding a digital watermark from a host signal, the digital watermark conveying a plural symbol message, the method including the acts:

• using a computer programmed as a digital watermark decoder to perform the acts of:
• processing the host signal to obtain an initial estimate of the plural symbols and reliability of the initial estimate;
• based on the initial estimate and the reliability of the initial estimate, adapting parameters of a predictive filter so that filter function is adapted based on the initial estimate;
• processing the signal using the predictive filter;
• and
• decoding the digital watermark from the processed signal.