The disclosure describes methods for adaptive prediction filtering for
digital watermarking applications. The predictive filter is designed to
predict the digital watermark signal. In one implementation, there are
two stages of prediction filtering. A first stage operates on a suspect
signal before detecting any watermark in that signal. This stage adapts
the predictive filter to local signal characteristics. A second stage
uses known watermark signal elements to adapt a non-linear filter used in
extracting message symbols from the suspect signal. This stage produces
detection statistics based on a comparison of expected and measured
message symbol values, and uses these statistics to adapt the parameters
of a predictive filter. This adapted prediction filter is then applied to
extract message symbol estimates.