Scrambling and descrambling techniques are described which, unlike many typical scrambling systems, are compatible with all conceivable forms of signal compression systems. The scrambling technique is based on the principle of applying local spatial distortion to the pixels in a video image, and the...http://www.google.de/patents/US6590979?utm_source=gb-gplus-sharePatent US6590979 - Method and apparatus for compression compatible video scrambling
