Watermarking

• US 7,130,443 B1
• Filed: 03/20/2000
• Issued: 10/31/2006
• Est. Priority Date: 03/18/1999
• Status: Expired due to Fees

• Current Assignee: British Broadcasting Corporation
• Original Assignee: British Broadcasting Corporation
• Inventors: Werner, Oliver Hartwig, Mason, Andrew James, Salmon, Richard Aubrey
• Primary Examiner(s): Wu, Jingge
• Assistant Examiner(s): Tabatabai, Abolfazl
• Application Number:
  US09/936,816
• Time in Patent Office: 2,416 Days
• Field of Search: 382/100, 382/232, 382/240, 380/51, 380/54, 380/201, 380/210, 380/252, 380/287, 713/176, 713/179, 358/3.28, 370522-529, 348/461, 348/463, 283 72- 81, 283/85, 283/93, 283/901, 283/902, 283/113, 725/20, 725/22, 375/130
• US Class Current: 382/100
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking

Abstract

A watermarking system and method is proposed for still or moving pictures in which a watermark is embedded robustly and simply into DC-values, but without causing unacceptable visible picture degradation. The watermark is secure and can be readily detected, and the method can be used to convey additional data. Also disclosed is a method for watermarking a sequence of pictures in which the visibility of artifacts is reduced. The watermark may carry data and may be used to label a program.

Claims

1. A method of embedding a watermark signal comprising a series of watermark values in a picture signal comprising a series of picture sample values, the method comprising adjusting picture sample values based on watermark values wherein the watermark is derived from a combination of a number of substantially independent watermarks or wherein a number of substantially independent watermarks are embedded in each picture wherein said substantially independent watermarks satisfy the following criteria:

—

w²₁= . . . =w²_N=1 

 

(1)

E[w₁]= . . . =E[w_N]=0, where E is the expectation operator 

 

(2)

E[w_k·

w_n]=0 if k≠

n 

 

(3).

2. A method according to claim 1, wherein said number of substantially independent watermarks comprises a subset selected from a defined set of substantially independent watermarks.

3. A method according to claim 2, wherein said number is three.

4. A method according to claim 2, wherein there are more than three substantially independent watermarks in said set.

5. A method according to claim 1, wherein the subset is selected or said substantially independent watermarks are selected in dependence on information to be encoded in the picture.

6. A method according to claim 1, wherein three bipolar watermarks are combined to produce a single bipolar watermark with the property that the product of the combined watermark with each of the constituent marks has an expectation value of ½

.

7. A method according claim 1 including generating the watermark by convolving a key with a repeated data sequence to produce a data-carrying watermark.

8. A method according to claim 1, wherein the picture is divided into two or more sub-pictures, and a substantially independent watermark is embedded into each sub-picture.