Feature-based watermarks and watermark detection strategies
View Patent ↗Processes and apparatus for improving the state of the art for watermarking and data protection. The disclosure includes feature-based watermarks, auto- and cross-correlation techniques for determining scaling and rotation, transitions in time based watermarking, autocorrelation watermarks for images, and dynamic content scrambling of static files.
1. A feature based embedding method for hiding auxiliary data in a media signal comprising:
identifying N features in the media signal, where N comprises an integer greater than one; and
embedding a signal around the N features by modulating sample values in a group of samples around each feature according to a signal layer, wherein the features comprise peaks of a mathematical derivative of the media signal.
2. The method of claim 1 wherein the media signal comprises an image.
3. The method of claim 1 wherein the signal comprises a noise layer.
4. A feature based watermark embedding method for hiding auxiliary data in a media signal comprising:
identifying N features in the media signal, where N comprises an integer greater than one; and
embedding a watermark around the N features by modulating sample values in a group of samples around each feature according to a watermark signal layer,
wherein different types of watermark signals are embedded into the media signal: a first type embedded around at least some of the N features in the media signal, and a second type embedded in at least some parts of the media signal.
5. The method of claim 4 wherein the media signal comprises an image.
6. The method of claim 5 wherein the features comprises peaks of the image.
7. The method of claim 6 wherein the features comprise peaks of the derivative of the image.
8. The method of claim 4 wherein the second type carries a message payload.
9. A feature based watermark embedding method for hiding auxiliary data in a media signal comprising:
identifying N features in the media signal, where N comprises an integer greater than one; and
embedding a watermark around the N features by modulating sample values in a group of samples around each feature according to a watermark signal layer, wherein the watermark signal has correlation properties that enable a watermark decoder to compensate for scaling distortion by computing auto or cross correlation of the watermarked signal and deriving scaling from positioning of peaks in a resulting signal.
10. A feature based watermark embedding method for hiding auxiliary data in a media signal comprising:
identifying N features in the media signal, where N comprises an integer greater than one; and
embedding a watermark around the N features by modulating sample values in a group of samples around each feature according to a watermark signal layer, wherein the watermark comprises a PN sequence of symbol values of either 1 or −1, the symbols are mapped to samples of the media signal, and transitions in phase between adjacent groups of samples corresponding to different symbols are made to change slowly.
11. A method of decoding a feature based watermark that hides auxiliary data in a media signal comprising:
identifying N features in the media signal, where N comprises an integer greater than one; and
decoding a watermark around the N features by correlating sample values in a group of samples around each feature with a watermark signal layer;
using one of the N features as a reference for decoding auxiliary data for one or more of the other features,
wherein multiple different watermark layers are decoded including watermark layers around the features and elsewhere.
12. The method of claim 11 wherein the watermark layers employ PN sequence carrier signals detected using cross correlation or autocorrelation functions on the watermarked signal.