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.
