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Robust digital watermarking
| Details |
Inventors: Cox, Ingemar J.; Miller, Matthew L.;
Assignee: NEC Laboratories America, Inc. (Princeton, NJ)
Primary Examiner: Johns; Andrew W.
Assistant Examiner: Nakhjavan; Shervin
Attorney, Agent or Firm:
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.times.n blocks, such as the 8.times.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.times.8 blocks to form a set of N summed 8.times.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. |
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DETAILED DESCRIPTION The present invention concerns a novel insertion method which employs a specific model of the human visual system which provides much better control over image fidelity.
Tests have shown that it is possible to obtain large signals (more than 15 standard deviations from 0 correlation) with images that are indistinguishable from their respective original images.
The method handles robustness against various types of attacks in ways that are easy to relate to the specific type of attack.
The method is adaptable so that the model of the human visual system and the techniques used for handling attacks can be changed later without having to change the detector.
The result is that it is possible to continue improving watermarking, particularly DVD (digital video disk) watermarking, even after many detectors have been installed.
This is analogous to the situation with MPEG video for which encoder technology can be improved without having to change existing decoders.
Use of the present insertion method allows a simple detection algorithm in either MPEG or decompressed domains.
The invention also concerns a novel detection method which is easy to implement, easy to analyze and has a low computational cost, whether the incoming video is MPEG compressed or uncompressed.
The present invention also concerns a novel insertion method that hides multiple patterns in the data.
These patterns fall into two categories: 1) registration patterns used during detection to compensate for translational shifts, and 2) watermark patterns that encode the information content of the watermark.
A principal object of the present invention is the provision of a digital watermark insertion method which allows detection of watermarks after the watermarked data is subjected to predefined scale changes, without modification to the watermark detector.
Another object of the invention is the provision of a watermark detection method that is computationally inexpensive in either the MPEG or decompressed domains
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TV Signal 
