Detection of multiple watermarks and improved watermark calibration signals
US6975744B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 20, 2001 |
| Grant date | Dec 13, 2005 |
| Priority date | — |
| Expiry date | Nov 6, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2201/0601
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Steganographic calibration signals (sometimes termed “orientation signals,” “marker signals,” reference signals,” “grid signals,” etc.) are sometimes included with digital watermarking signals so that subsequent distortion of the object thereby marked (e.g., a digital image file, audio clip, document, etc.) can later be discerned and compensated-for. Digital watermark detection systems sometimes fail if the object encompasses several separately-watermarked components (e.g., a scanned magazine page with several different images, or photocopy data resulting from scanning while several documents are on the photocopier platen). Each component may include its own calibration signal, confusing the detection system. In accordance with certain embodiments, this problem is addressed by a proximity-based approach, and/or a multiple grid-based approach. In accordance with other embodiments, the calibration signal can—itself—convey watermark information, so it serves both a calibration and a payload-conveyance function.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.