On Tuesdays, the USPTO issues new patents, and Chrismas was no exception. Both of today's spotlight patents address various aspects of watermarking. Assigned to the US Government, the first describes techniques for frequency domain watermarking using a phase based filter signature. Assigned to Hitachi, the second patent addresses ways of detecting digital watermark information.
7,313,250, "Method and system for frequency domain watermarking using a phase based filter signature," assigned to the US Government (Navy).
The present invention is a digital watermarking technique Phasemark.TM. for image authentication. Using a signature extracted from the original image, the present invention hides an encoded version of the signature back into the original image, forming the watermarked image. The hiding is done in the frequency domain. Specifically, the present invention is a new transform domain digital watermarking technique that hides a signature obtained from the Fourier phases into the magnitude spectrum of the same host image. The detection process computes the discrete Fourier transform of the watermarked image, extracts and decodes the embedded signature, and then correlates it with calculated phase information. Correlation metrics determine the degree of authenticity of the image.
7,310,428, "Method of detecting digital watermark information," assigned to Hitachi.
The present invention can detect watermark information from motion picture of various scanning methods and various picture sizes without causing increase of a memory capacity.A watermark information detection apparatus 1 converts encoded watermarked motion picture 4 into standard motion picture 5 having the smallest data size among the assumed kinds of motion picture. Further, the watermark information detection apparatus 1 scales a standard coordination system that is utilized for specifying embedding locations of a watermark pattern. Then, with respect to each field of the standard motion picture 5, watermark information is detected from predetermined locations specified in the scaled standard coordinate system by the watermark pattern.