Watermarking an information signal
AssigneeKoninklijke Philips Electronics N.V.
InventorJohan P.M.G. Linnartz
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Abstract
A method and an arrangement for detecting a multi-bit watermark in a signal (e.g. a video image) are disclosed. Each bit of the multi-bit value is represented by an embedded watermark subpattern in the signal. Instead of detecting in a conventional manner the presence of each individual subpattern (i.e. detecting each individual bit), the detection comprises the steps of: detecting (24, 23) the presence of the full watermark in the signal irrespective of its multi-bit value, and detecting (25) to which extent the presence of subpatterns corresponds with the multi-bit value to be checked. The reliability of watermark detection is hereby improved.
Claims6
A method of detecting a multi-bit watermark in a signal, each bit (w(n)) of said multi-bit watermark being represented by a respective watermark subpattern, comprising the steps of:
- determining (21, 22), for each watermark subpattern, a correlation value (y(n)) indicating the extent to which said subpattern is present in the signal;
- combining (24, 23) said correlation values to detect (D) whether the watermark is present in the signal irrespective of its multi-bit value;
- and
- comparing (25) said correlation values (y(n)) and the corresponding bits (w(n)) of an applied multi-bit value to obtain an indication (M) of to which extent the detected watermark has said applied multi-bit value.
An arrangement for detecting a multi-bit watermark in a signal, each bit (w(n)) of said multi-bit watermark being represented by a respective watermark subpattern, comprising:
- means for determining (21, 22), for each watermark subpattern, a correlation value (y(n)) indicating the extent to which said subpattern is present in the signal;
- means for combining (24, 23) said correlation values to detect (D) whether the watermark is present in the signal irrespective of its multi-bit value;
- and
- means for comparing (25) said correlation values (y(n)) and the corresponding bits (w(n)) of an applied multi-bit value to obtain an indication (M) of to which extent the detected watermark has said applied multi-bit value.
A method of embedding a multi-bit watermark in a video image by adding a watermark pattern to said image, comprising the-steps of:
- dividing (11, 12) the video image and said watermark pattern into blocks, the blocks of the watermark pattern constituting subpatterns;
- and
- representing (10) each bit (w1 . . . wn) of the multi-bit value by adding or not adding a subpattern to the corresponding image block.
An arrangement for embedding a multi-bit watermark in a video image (P) by adding a watermark pattern (W) to said image, comprising:
- means for dividing (11, 12) the video image and said watermark pattern into blocks, the blocks of the watermark pattern constituting subpatterns;
- and
- means for adding (10) or not adding a subpattern to a corresponding image block in accordance with a corresponding bit (w1 . . . wn) of the multi-bit value.
Dependencies are inferred from the claim text.