| 摘要 |
A method and apparatus for scrambling a composite television signal and a method and apparatus for unscrambling of the scrambled television signal are disclosed in the present application. The method of scrambling shifts at least some lines of video information relative to adjacent (preceding or subsequent) lines of video information according to a predetermined scheme, and deletes at least some portions of the signal which comprise synchronization or control information of a known or predetermined repetitive form from between at least some of the adjacent shifted lines of video information. The method of unscrambling applies a complementary shift to return the video information into proper time spacing and includes the insertion of any necessary synchronization information eliminated from the signal during the scrambling. In the preferred form of the invention, lines of video information are shifted in a manner to eliminate at least some horizontal synchronization pulses which are inserted during unscrambling. Timing information is preferrably encoded in the scrambled signal to allow the unscrambler to reverse the scrambling operation and insert any necessary synchronization information. It is possible to shift various lines of video information in a manner to eliminate at least some of the horizontal synchronization information while maintaining essentially all of the lines of video information necessary to allow unscrambling of the signal to produce a signal suitable for faithful reproduction on a television. |
