Robust digital watermarking
First Claim
1. A method of detecting a watermark from watermarked data comprising the steps of:
- receiving watermarked data where the watermarked data comprises n×
n blocks of watermarked data;
summing the n×
n blocks of watermarked data to form at least one n×
n block of summed watermarked data;
cyclically shifting the block in the spatial domain to register the block, and extracting the watermark from the at least one n×
n block.
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Accused Products
Abstract
A watermarking procedure that is applicable to images, audio, video and multimedia data to be watermarked divides the data to be watermarked into a set of n×n blocks, such as the 8×8 blocks of MPEG. The same watermark signal can be distributed throughout the set of blocks in a large variety of ways. This allows the insertion algorithm to be changed without affecting the decoders. The decoding procedure first sums together the DCT coefficients of N sets of 8×8 blocks to form a set of N summed 8×8 blocks and then extracts the watermark from the summed block. Since the sum of the DCT blocks is equal to the DCT of the sum of the intensity blocks, efficient decoding can occur in both the spatial and frequency domains. The symmetric nature of the decoding process allows geometric distortions to be handled in the spatial domain and other signal distortions to be handled in the frequency domain. Moreover, insertion of a watermark signal into image data and the subsequent extraction of the watermark from watermarked image data which has been subject to distortion between the times of insertion and extraction involves the insertion of multiple watermarks designed to survive predefined distortions of the image data, such as panscan or letterbox mode transformations. Alternatively, a registration pattern in the image data, after the image data containing the registration pattern is subject to an unknown distortion, is used to compensate for distortion of the watermarked image data.
104 Citations
17 Claims
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1. A method of detecting a watermark from watermarked data comprising the steps of:
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receiving watermarked data where the watermarked data comprises n×
n blocks of watermarked data;
summing the n×
n blocks of watermarked data to form at least one n×
n block of summed watermarked data;
cyclically shifting the block in the spatial domain to register the block, and extracting the watermark from the at least one n×
n block.
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2. A method detecting a watermark from watermarked data comprising the steps of:
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receiving watermarked data where the watermarked data comprises n×
n blocks of watermarked data;
summing the n×
n blocks of watermarked data to form at least one n×
n block of summed watermarked data, andextracting the watermark from the at least one n×
n block by summing predetermined watermarked data from each n×
n block to yield each element of the extracted watermark.- View Dependent Claims (3, 4, 5)
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6. A method of detecting a watermark from watermarked data comprising the steps of:
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receiving watermarked data where the watermarked data comprises n×
n blocks of watermarked data;
summing the n×
n blocks of watermarked data to form M n×
n blocks of summed watermarked data, where M is the number of functions mapping frequency indices onto the indices of elements of watermarks, andextracting the watermark from the at least one n×
n block.- View Dependent Claims (7, 8)
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9. A method of inserting an extractable watermark signal into image data so that the watermark signal can be extracted after the watermarked data is subject to distortion comprising the steps of:
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receiving image data in form of n×
n blocks; and
inserting an n×
n registration pattern into the image datawherein the registration pattern is a spatial pattern inserted into the image such that the sum of all pixel blocks highly correlates with the pattern. - View Dependent Claims (10)
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11. A method of detecting a watermark from watermarked image data that has been subjected to a two dimensional translation distortion comprising the steps of:
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partitioning received distorted watermarked image data into a set of n×
n blocks;
summing together watermarked image data in a predetermined number of n×
n blocks;
if summed n×
n blocks are not in spatial domain, transforming summed n×
n blocks into spatial domain;
determining two-dimensional translation distortion of the summed n×
n blocks;
shifting the summed n×
n blocks according to the determined distortion;
transforming the shifted n×
n blocks into transform domain;
extracting a possible watermark signal from the transformed n×
n blocks;
correlating the possible watermark with a known watermark;
repeating said correlating for cyclic shifts of the possible watermark; and
determining the presence of a watermark based on said correlating. - View Dependent Claims (12, 13, 14)
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15. A method of detecting a watermark from watermarked image data that has been subjected to a two dimensional translation distortion comprising the steps of:
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(a) partitioning received distorted watermarked image data into n×
n blocks;
(b) summing together watermarked image data in a predetermined number of n×
n blocks;
(c) if summed n×
n blocks are not in spatial domain, transforming summed n×
n blocks into spatial domain;
(d) shifting the summed n×
n n blocks by one of n2 possible shifts;
(e) transforming the shifted n×
n blocks into transform domain;
(f) extracting a possible watermark signal from the transformed n×
n blocks;
(g) correlating the possible watermark with a known watermark;
(h) repeating said correlating for cyclic shifts of the possible watermark;
(i) repeating steps (d)-(h) for each of the n2 possible shifts; and
(j) determining the presence of a watermark based on the results of step (i). - View Dependent Claims (16, 17)
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Specification