Watermarking an informational signal
First Claim
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1. Apparatus for detection of a watermark in an information signal, comprising:
- means for receiving said information signal, said signal having therein a series of multi-bit watermark values, each such bit value representing a respective watermark subpattern;
means for determining, for each watermark subpattern, a correlation value y(n) indicative of whether or not said subpattern is present in the information signal;
means for combining the correlation values of all subpatterns to determine (D) the presence of an applied multi-bit value watermark pattern in the information signal regardless of the multi-bit value of the applied watermark pattern; and
means for comparing the correlation values of all subpatterns with a corresponding bit value of the applied watermark multi-bit values to obtain an indication (M) of the extent which the multi-bit values of the detected watermark patterns corresponds to the multi-bit value of the applied watermark pattern.
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Abstract
A multi-bit watermark is detected in a signal (e.g. a video image) in which each bit of the multi-bit value is represented by an embedded watermark subpattern in the signal. The watermark is detected by first detecting the presence of the full watermark in the signal irrespective of its multi-bit value, and then detecting to which extent the presence of subpatterns corresponds with the multi-bit value to be checked.
97 Citations
5 Claims
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1. Apparatus for detection of a watermark in an information signal, comprising:
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means for receiving said information signal, said signal having therein a series of multi-bit watermark values, each such bit value representing a respective watermark subpattern;
means for determining, for each watermark subpattern, a correlation value y(n) indicative of whether or not said subpattern is present in the information signal;
means for combining the correlation values of all subpatterns to determine (D) the presence of an applied multi-bit value watermark pattern in the information signal regardless of the multi-bit value of the applied watermark pattern; and
means for comparing the correlation values of all subpatterns with a corresponding bit value of the applied watermark multi-bit values to obtain an indication (M) of the extent which the multi-bit values of the detected watermark patterns corresponds to the multi-bit value of the applied watermark pattern.
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2. A method of improving the reliability of detection of a watermark in an information signal, comprising the steps of:
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providing a series of multi-bit watermark values w(n) in said information signal, each such bit value representing a respective watermark subpattern;
determining, for each watermark subpattern, a correlation value y(n) indicative of whether or not said subpattern is present in the information signal;
combining the correlation values of all subpatterns to detect (D) the presence of an applied multi-bit value watermark pattern in the information signal regardless of the multi-bit value of the applied watermark pattern; and
comparing the correlation values of all subpatterns with a corresponding bit value of the applied watermark pattern multi-bit values to obtain an indication (M) of the extent to which the multi-bit value of the detected watermark pattern corresponds to the multi-bit value of the applied watermark pattern. - View Dependent Claims (3, 4, 5)
adding a watermark pattern to the image;
dividing the video image and the watermark pattern into blocks, the blocks of the watermark pattern constituting the subpatterns; and
representing each bit of the multi-bit values by whether or not a subpattern of the subpatterns is added to a corresponding image block.
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4. The method of claim 2, wherein the information signal represents a video image which is watermarked by adding a watermark pattern to the image, the video image and the watermark pattern being divided into blocks, the blocks of the watermark pattern constituting the subpatterns, and wherein each bit value of the watermark pattern multi-bit values represents whether or not a subpattern has been added to a corresponding image block.
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5. The method of claim 2, wherein the step of comparing includes calculating the sum of squares of differences between each correlation value and a corresponding bit value of the multi-bit values of the applied watermark pattern.
Specification