Data processing: generic control systems or specific application – Generic control system – apparatus or process – Optimization or adaptive control
Reexamination Certificate
1999-11-04
2002-11-05
Patel, Ramesh (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Optimization or adaptive control
C700S026000, C700S027000, C700S030000, C700S038000, C700S052000, C700S058000, C382S135000, C382S212000, C382S232000, C382S235000, C382S251000, C382S181000, C713S176000, C713S179000, C713S152000, C380S054000, C380S201000, C380S206000, C380S239000
Reexamination Certificate
active
06477431
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method of detecting a watermark in an information signal that has possibly been watermarked by modifying values of said information signal in accordance with (temporally or spatially) corresponding values of a watermark pattern. The invention also relates to an arrangement for detecting a watermark.
BACKGROUND OF THE INVENTION
A prior art method as defined in the opening paragraph is disclosed in International Patent Application WO-A-98/03014. The watermark is detected by computing the correlation of the suspect information signal with an applied watermark pattern, and comparing the correlation with a predetermined threshold. If the correlation is larger than the threshold, the watermark is said to be present, otherwise it is said to be absent.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a suitable criterion for setting the threshold.
To this end, the invention provides a method of detecting a given watermark in an information signal, comprising the steps of: computing the correlation of said watermark and said information signal for a plurality of positions of said watermark with respect to said information signal; and detecting whether at least one of the respective correlation values exceeds a given threshold; characterized in that the method comprises the step of determining the standard deviation of the respective correlation values, wherein said given threshold is a given multiple of said standard deviation.
The invention exploits the insight that watermark detectors need to compute the correlation value for a plurality of (temporal or spatial) positions of the watermark with respect to the information signal (for example, an image) in practice, because the position of the watermark with respect to image is not absolutely known and/or information is embedded in shifts of one or more watermark patterns. The detection thus yields a series of correlation values, and it is the occurrence of relative peaks in such a series which is of interest rather than absolute correlation values.
REFERENCES:
patent: 4669344 (1987-06-01), Herrig
patent: 5960081 (1999-09-01), Vynne et al.
patent: 6198832 (2001-03-01), Maes et al.
patent: 6246775 (2001-06-01), Nakamura et al.
patent: 6252972 (2001-06-01), Linnartz
patent: 6341350 (2002-01-01), Miyahara et al.
patent: WO9803014 (1997-06-01), None
patent: WO-99/12347 (1999-03-01), None
US 2002/0009208 A1, Alattar et al., Jan. 24, 2002, Authentication of Physical and Electronic Media Objects Using Digital Watermarks.*
US 2002/0015509 A1, Nakamura et al., Feb. 7, 2002, Method and Apparatus for Superposing a Digital Watermark and Method and Apparatus for Detecting a Digital Watermark.
Depovere Geert F. G.
Haitsma Jaap A.
Kalker Antonius A. C. M.
Linnartz Johan P. M. G.
Maes Maurice J. J. J.-B
Koninklijke Phillips Electronics, NV
Patel Ramesh
Thorne Gregory L.
LandOfFree
Watermark detection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Watermark detection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Watermark detection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2983992