Robust digital watermarking

• US 6,278,792 B1
• Filed: 04/26/2000
• Issued: 08/21/2001
• Est. Priority Date: 06/24/1998
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Research Institute, Inc. (NEC Corporation)
• Inventors: Cox, Ingemar J., Miller, Matthew L., Oami, Ryoma
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): NAKHJAVAN, SHERVIN K
• Application Number:
  US09/559,808
• Time in Patent Office: 482 Days
• Field of Search: 382/100, 382/232, 713/176
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32165 using cosine transforms
• CPC Class Codes: H04N 1/32192 according to calculated or estimated visibility of the additional information in the image
• CPC Class Codes: H04N 1/32277 Compression
• CPC Class Codes: H04N 1/32304 Embedding different sets of additional information
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 21/8358 involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• CPC Class Codes: H04N 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 7/24 Systems for the transmission of television signals using pulse code modulation H04N21/00 takes precedence

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.

Claims

1. 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:

providing image data to be watermarked;

copying the image data;

applying a predefined distortion to the copy of image data;

inserting a watermark signal into the distorted copy of image data;

subtracting the copy of distorted image data from the watermarked copy of distorted image data to generate a watermark pattern;

performing inverse distortion on the watermark pattern to generate the watermarked pattern for nondistorted image data, and

combining said image data to be watermarked and said watermark pattern for nondistorted image data to obtain watermarked data.

2. A method of inserting a watermark signal into image data as set forth in claim 1, where said predetermined distortion is panscan mode image data.

3. A method of inserting a watermark signal into image data as set forth in claim 1, where said predetermined distortion is letterbox mode image data.

4. A method of inserting a watermark signal into image data as set forth in claim 1, where said combining includes combining with perceptual modeling.