Time-varying video watermark

• US 7,197,164 B2
• Filed: 11/01/2005
• Issued: 03/27/2007
• Est. Priority Date: 09/11/2000
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Levy, Kenneth L.
• Primary Examiner(s): Johns; Andrew W.
• Application Number:
  US11/265,766
• Publication Number:
  US 20060120559A1
• Time in Patent Office: 511 Days
• Field of Search: 382/100, 382/232, 713/176, 380/201, 380/210, 380/252, 380/287, 380/54, 348/461, 348/463, 348/467
• 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 1/0042 Fragile watermarking, e.g. so as to detect tampering
• CPC Class Codes: G06T 1/0071 using multiple or alternating watermarks
• CPC Class Codes: G06T 1/0085 Time domain based watermarking, e.g. watermarks spread over several images
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: H04L 67/06 specially adapted for file transfer, e.g. file transfer protocol [FTP]
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/3216 using Fourier transforms
• CPC Class Codes: H04N 17/004 for digital television systems
• CPC Class Codes: H04N 21/4425 Monitoring of client processing errors or hardware failure
• 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

Abstract

A digital watermark embedder reduces a watermark signal as a function of time varying properties of video such that a watermark that would otherwise be static over frames is selectively reduced to make it imperceptible. The method computes a watermark signal corresponding to locations within a frame, where the watermark signal is mapped to locations in the video frame and is computed based upon attributes of the video within the frame. The method varies the strength of the watermark signal over time. The process of varying the strength includes reducing the strength of the watermark signal to make the digital watermark less perceptible in the video in locations where the video has time varying properties. The method embeds the watermark signal into the video at the locations with the varying strength.

Claims

1. A method of embedding a digital watermark into a video signal such that the digital watermark is substantially imperceptible in the video signal, the method comprising:

computing a watermark signal corresponding to locations within a frame, where the watermark signal is mapped to locations in the video frame and is computed based upon attributes of the video within the frame;

varying strength of the watermark signal over time;

the varying including reducing the strength of the watermark signal to make the digital watermark less perceptible in the video in locations where the video has time varying properties; and

embedding the watermark signal into the video at the locations with the varying strength.

2. The method of claim 1 wherein the watermark signal corresponds to a carrier signal that is modulated to carry variable message data.

3. The method of claim 2 wherein the modulated carrier is based on a pseudorandom sequence.

4. The method of claim 1 wherein the watermark signal is mapped in a manner that scrambles locations of watermark elements in the video signal.

5. The method of claim 1 wherein the strength of the watermark signal is varied relative to a reference value.

6. The method of claim 5 wherein the reference value comprises a gain value used to control strength of the watermark signal.

7. The method of claim 6 wherein the reference value is further dependent on an intra frame gain computed based on non-temporal attributes within a frame.

8. The method of claim 5 wherein the watermark signal is varied relative to the reference value according to a dither signal.

9. A machine readable medium on which is stored instructions for performing a method of embedding a digital watermark into a video signal such that the digital watermark is substantially imperceptible in the video signal, the method comprising:

computing a watermark signal corresponding to locations within a frame, where the watermark signal is mapped to locations in the video frame and is computed based upon attributes of the video within the frame;

varying strength of the watermark signal over time;

the varying including reducing the strength of the watermark signal to make the digital watermark less perceptible in the video in locations where the video has time varying properties; and

embedding the watermark signal into the video at the locations with the varying strength.

10. The machine readable medium of claim 9 wherein the watermark signal corresponds to a carrier signal that is modulated to carry variable message data.

11. The machine readable medium of claim 10 wherein the modulated carrier is based on a pseudorandom sequence.

12. The machine readable medium of claim 9 wherein the watermark signal is mapped in a manner that scrambles locations of watermark elements in the video signal.

13. The machine readable medium of claim 9 wherein the strength of the watermark signal is varied relative to a reference value.

14. The machine readable medium of claim 13 wherein the reference value comprises a gain value used to control strength of the watermark signal.

15. The machine readable medium of claim 14 wherein the reference value is further dependent on an intra frame gain computed based on non-temporal attributes within a frame.

16. The machine readable medium of claim 13 wherein the watermark signal is varied relative to the reference value according to a dither signal.

17. A method of embedding a digital watermark into a video signal such that the digital watermark is substantially imperceptible in the video signal, the method comprising:

computing a watermark signal corresponding to locations within the video, where the watermark signal is mapped to locations in the video and is computed based upon attributes of the video within the frame;

varying strength of the watermark signal over time;

the varying including selectively reducing the strength of the watermark signal relative to a reference value to make the digital watermark less perceptible in the video in locations where the video has time varying properties that otherwise cause the watermark signal to be more perceptible; and

embedding the watermark signal into the video at the locations with the varying strength.

18. The method of claim 17 wherein varying the strength includes varying the strength as a function of changes in pixel values over time.

19. The method of claim 17 wherein varying the strength includes varying according to a dither signal.

20. The method of claim 17 wherein varying includes varying based on a prediction of future changes in pixel values based on past changes in pixel values.