Described herein is an audio watermarking technology for detecting watermarks
in audio signals, such as a music clip. The watermark identifies the content producer,
providing a signature that is embedded in the audio signal and cannot be removed.
The watermark is designed to survive all typical kinds of processing and all types
of malicious attacks that attempt to remove or modify the watermark from the signal.
The implementations of the watermark detecting system, described herein, support
quick, efficient, and accurate detection of watermarks by the specifically designed
watermark detecting system. In one described implementation, a watermark detecting
system employs an improved normalized covariance test to determine the presence
of a watermark using less expensive materials (hardware), quicker calculations,
and a more accurate test (than the original correlation test). In other described
implementations, a watermark detecting system employs a cepstrum filter and dynamic
processing to minimize the affect of the "noise" in the watermarked signal. The
"noise" is the original content of the signal before such signal was watermarked.
In still another described implementation, a watermark detecting system employs
a mechanism for random detection threshold so that the act of watermark detection
does not provide decipherable clues to a digital pirate as to the value or location
of the embedded watermark.
