Human perceptual model applied to rendering of watermarked signals

• US 7,352,878 B2
• Filed: 04/15/2004
• Issued: 04/01/2008
• Est. Priority Date: 04/15/2003
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Reed, Alastair M., Rogers, Eliot
• Primary Examiner(s): Werner; Brian
• Assistant Examiner(s): Rice; Elisa M
• Application Number:
  US10/826,970
• Publication Number:
  US 20050157907A1
• Time in Patent Office: 1,447 Days
• Field of Search: None
• 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 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
• CPC Class Codes: H04N 1/32149 Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/32192 according to calculated or estimated visibility of the additional information in the image
• CPC Class Codes: H04N 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 1/3232 Robust embedding or watermarking

Abstract

A digital watermarking system uses a model of a rendering device to take into account the impact of the rendering device on visual or auditory quality of the watermarked signal. For visual content, a reference image and watermarked image are passed through the model and then supplied to a visual quality metric that assesses the visibility of the watermark. The digital watermark embedding is adjusted iteratively with each pass through this process to produce a watermarked signal that has the desired visual quality.

Claims

1. A method of digitally watermarking visual media comprising:

passing a reference image and a watermarked image through a model of an output device to produce a modeled reference image and a modeled watermarked image, the reference image comprising a version of the watermarked image prior to being watermarked to form the watermarked image;

passing the modeled reference image and the modeled watermarked image to a visual quality metric that computes a measure of visual quality of the modeled watermarked image based on a visual quality analysis of the modeled watermarked image relative to the modeled reference image; and

using the output of the quality metric to adjust watermark embedding to achieve a desired visual quality in a watermarked image.

2. The method of claim 1 wherein the visual media comprises an image to be printed and the model is a model of a printing process.

3. The method of claim 1 wherein the visual media comprises video to be displayed and the model is a model of a display device.

4. The method of claim 1 including:

applying the model of the output device and visual quality metric iteratively to adjust the watermark embedding.

5. The method of claim 1 wherein the visual quality metric is used to produce a visibility map, and the visibility map is input to the watermark embedding to adjust areas of the digital watermark so as to compensate for an effect of the output device on visual quality of the watermarked image.

6. The method of claim 1 wherein the visual quality metric evaluates a watermarked image relative to an original un-watermarked image to identify areas in the watermarked image where an embedded digital watermark is more or less visible.

7. A computer readable storage medium on which is stored instructions for performing a method of digitally watermarking visual media, the method comprising:

passing a reference image and a watermarked image through a model of an output device to produce a modeled reference image and a modeled watermarked image, the reference image comprising a version of the watermarked image prior to being watermarked to form the watermarked image;

passing the modeled reference image and the modeled watermarked image to a visual quality metric that computes a measure of visual quality of the modeled watermarked image based on a visual quality analysis of the modeled watermarked image relative to the modeled reference image; and

using the output of the quality metric to adjust watermark embedding to achieve a desired visual quality in a watermarked image.

8. A method of digitally watermarking a signal comprising:

passing a reference signal and a watermarked signal through a model of an output device to produce a modeled reference signal and a modeled watermarked signal, the reference signal comprising a version of the watermarked signal prior to being watermarked to form the watermarked signal;

passing the modeled reference signal and the modeled watermarked signal to a perceptual quality metric that computes a measure of perceptual quality of the modeled watermarked signal based on a perceptual quality analysis of the modeled watermarked signal relative to the modeled reference signal; and

using the output of the quality metric to adjust watermark embedding to achieve a desired perceptual quality in a watermarked signal.

9. The method of claim 8 wherein the model of the output device models an effect of an audio rendering process.

10. The method of claim 8 wherein the model of the output device models an effect of a video rendering process.

11. The method of claim 8 wherein the model of the output device models an effect of a printing process.

12. The method of claim 8 wherein the output of the quality metric is used to adjust strength of digital watermark embedding in areas of the watermarked signal where the perceptual quality metric determines that a digital watermark is more or less perceptible than desired.

13. The method of claim 12 wherein the adjusting is performed by providing output from the quality metric to input of a digital watermark embedding process.

14. The method of claim 13 including providing output from the quality metric to the digital watermark embedding process in a visibility map used to adjust strength of digital watermark embedding in areas of the signal.

15. The method of claim 12 wherein the adjusting is performed iteratively by repeatedly applying the model of the output device and the quality metric to watermarked signals and using output of the quality metric to adjust the watermark embedding until a desired perceptual quality of the watermarked signal is attained.

16. A computer readable storage medium on which is stored instructions for performing a method of digitally watermarking a signal, the method comprising:

passing a reference signal and a watermarked signal through a model of an output device to produce a modeled reference signal and a modeled watermarked signal, the reference signal comprising a version of the watermarked signal prior to being watermarked to form the watermarked signal;

passing the modeled reference signal and the modeled watermarked signal to a perceptual quality metric that computes a measure of perceptual quality of the modeled watermarked signal based on a perceptual quality analysis of the modeled watermarked signal relative to the modeled reference signal; and

using the output of the quality metric to adjust watermark embedding to achieve a desired perceptual quality in a watermarked signal.