Method and apparatus for preventing removal of embedded information in cover signals
US6145081A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 2, 1998 |
| Grant date | Nov 7, 2000 |
| Priority date | — |
| Expiry date | Feb 2, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2005/91335
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus and methods are provided for embedding watermark information into a cover signal, 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 prior to being embedded with the watermark information, wherein the amount or degree of phase modulation is changed 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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.