Time and object based masking for video watermarking

• US 6,961,444 B2
• Filed: 09/10/2001
• Issued: 11/01/2005
• 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:
  US09/951,142
• Publication Number:
  US 20020076083A1
• Time in Patent Office: 1,513 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

The disclosure describes a method of embedding a digital watermark into a video signal using a time based perceptual mask such that the digital watermark is substantially imperceptible in the video signal. A digital watermark embedder computes a time based perceptual mask comprising gain values corresponding to locations within a frame. The gain value for a location in the frame is changed as a function of the change in one or more pixel values at the location over time. The embedder uses the gain values of the time based perceptual mask to control embedding of corresponding elements of a digital watermark signal such that the perceptibility of the elements of the digital watermark signal is reduced in time varying locations of the video signal.

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 time based perceptual mask comprising gain values corresponding to locations within a frame, where the gain value for a location in the frame is changed as a function of the change in one or more pixel values at the location over time; and

using the gain values of the time based perceptual mask to control embedding of corresponding elements of a digital watermark signal such that the perceptibility of the elements of the digital watermark signal is reduced in time varying locations of the video signal;

wherein the gain is reduced at a location in a frame of video where changes in pixel values over time at that location indicate that data hiding capacity of the location is reduced.

2. 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 time based perceptual mask comprising gain values corresponding to locations within a frame, where the gain value for a location in the frame is changed as a function of the change in one or more pixel values at the location over time; and

using the gain values of the time based perceptual mask to control embedding of corresponding elements of a digital watermark signal such that the perceptibility of the elements of the digital watermark signal is reduced in time varying locations of the video signal;

wherein the gain is reduced at a location in a frame of video where the change in pixel values over time is highly varying, indicating that the data hiding capacity of the location is reduced.

3. 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 time based perceptual mask corresponding to locations within a frame, where the watermark for a location in the frame is embedded as a function of the change in one or more pixel values at the location over time; and

using the perceptual mask to control embedding of corresponding elements of a digital watermark signal such that the perceptibility of the elements of the digital watermark signal is reduced in time varying locations of the video signal;

wherein watermark embedding is reduced at a location in a frame of video where changes in pixel values over time at that location indicate that data hiding capacity of the location is reduced.

4. The method of claim 3 wherein the watermark embedding modulates a carrier signal as a function of variable message data.

5. The method of claim 4 wherein the modulated carrier is based on a pseudorandom sequence.

6. The method of claim 3 wherein the watermark embedding is a function of a mapping function that scrambles locations of watermark elements in the video signal.

7. A tangible 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 time based perceptual mask corresponding to locations within a frame, where the watermark for a location in the frame is embedded as a function of the change in one or more pixel values at the location over time; and

using the perceptual mask to control embedding of corresponding elements of a digital watermark signal such that the perceptibility of the elements of the digital watermark signal is reduced in time varying locations of the video signal;

wherein watermark embedding is reduced at a location in a frame of video where changes in pixel values over time at that location indicate that data hiding capacity of the location is reduced.

8. The method of claim 7 wherein the watermark embedding modulates a carrier signal as a function of variable message data.

9. The method of claim 8 wherein the modulated carrier is based on a pseudorandom sequence.

10. The method of claim 7 wherein the watermark embedding is a function of a mapping function that scrambles locations of watermark elements in the video signal.