| 摘要 |
<p>Apparatus and methods are provided for embedding watermark information into a cover signal (2), such as an audio signal, video signal, or still image signal, in a manner that prevents the watermark information from being removed without degrading the quality of the cover signal. This is accomplished by subjecting the cover signal to a phase modulation (6) prior to being embedded with the watermark information (8), wherein the amount or degree of phase modulation is changed (3, 5) at least for each different watermark to be embedded in a particular instance or copy of the cover signal. As such, if two copies of the same cover signal, each containing a different watermark, are averaged or combined in an attempt to obliterate the watermark information, the cover signal will be subjected to phase cancellation, rendering any illicit copy of such signal so derived to be valueless.</p> |
