Importance

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Abstract

Apparatus for intermittently or partially scrambling a digital video signal which encodes a digital video signal and successively supplies frames of video data corresponding to the encoded digital video signal. Each frame of video data has a respective frame number and respective blocks of video data, and each block of video data has a respective block number. Frame-scramble-off data is added to each frame which has a frame number equal to one of a plurality of predetermined frame numbers, and block-scramble-off data is added to each block which has a block number equal to one of a plurality of predetermined block numbers. A frame of video data is scrambled in the intermittent scrambling mode if it does not have the frame-scramble-off data and each block of video data is scrambled in the partial scramble mode if it does not have the block-scramble-off data. The scrambled frames or blocks of video data and the frames or blocks which are not scrambled are supplied as the scrambled digital video signal. The scrambled digital video signal is descrambled by receiving frames of video data of the scrambled signal, where each frame has either frame scramble-on data or frame scramble-off data, and respective blocks of video data, where each block has either block scramble-on data or block scramble-off data. Each block which has the block scramble-on data of those frames which have the frame scramble-on data are then descrambled to provide a descrambled digital video signal.

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First Claim