Video transmission system using time-warp scrambling
First Claim
1. An encoder for generating a scrambled composite video signal for secure transmission, the video signal having a plurality of video lines, each video line including a video data portion, said encoder comprising the combination of:
- means for sampling the video data portion for each video line at a periodic rate and subdividing the video data portion for each video line into a plurality of segments,a pseudorandom number generator for generating a plurality of pseudorandom number for at least some of said video lines, each pseudorandom number having multiple bits,video scrambling means responsive to said pseudorandom numbers for inverting the polarity of the samples in selected segments, for reversing the order of the samples in selected segments, and for reversing the order of the segments in selected segment pairs.
0 Assignments
0 Petitions
Accused Products
Abstract
A subscriber cable television system using predominantly digital signal processing techniques employs an improved time-warp and segment scrambling method for providing extremely high security. Means are also disclosed for suppressing the undesirable effects of discontinuities in the scrambled video signal by methods of inserting additional data samples between adjacent continuous segments, and by dithering the video line positions of the discontinuities. Preferably the scrambler and descrambler each have a memory for storing video samples, first and second address counters for providing read and write addresses to the memory, and means for decrementing or inhibiting address counting during the time between segments of continuous video samples in order to insert and delete samples during scrambling and descrambling, respectively.
94 Citations
44 Claims
-
1. An encoder for generating a scrambled composite video signal for secure transmission, the video signal having a plurality of video lines, each video line including a video data portion, said encoder comprising the combination of:
-
means for sampling the video data portion for each video line at a periodic rate and subdividing the video data portion for each video line into a plurality of segments, a pseudorandom number generator for generating a plurality of pseudorandom number for at least some of said video lines, each pseudorandom number having multiple bits, video scrambling means responsive to said pseudorandom numbers for inverting the polarity of the samples in selected segments, for reversing the order of the samples in selected segments, and for reversing the order of the segments in selected segment pairs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. An encoder for generating a scrambled composite video signal for secure transmission, the video signal having a plurality of video lines, each video line including a video data portion, said encoder comprising the combination of:
-
means for sampling the video data portion for each video line at a periodic rate and subdividing the video data portion for each video line into a plurality of segments, and means for inserting additional data samples between adjacent segments, one of said additional samples having the same value as that of the last sample of one of the adjacent segments, one of said additional samples having the same value as that of the first sample of the other of the adjacent segments, and one of said additional samples having a value equal to the average of the value of the other two additional samples, so that undesirable effects from discontinuities between adjacent segments are substantially reduced.
-
-
24. An encoder for generating a scrambled composite video signal for secure transmission, the video signal having a plurality of video lines, each video line including a video data portion, said encoder comprising the combination of:
-
means for sampling the video data portion for each video line at a periodic rate and subdividing the video data portion for each video line into a plurality of segments, means for altering a major portion of said segments in a major portion of said lines in accordance with a predefined pseudorandom code containing at least five bits per segment pair, means for inverting the polarity of a first segment in each pair in response to a first of said bits, means for inverting the polarity of a second segment in each pair in response to a second of said bits, means for reversing the order of the samples in a first segment in each pair in response to a third of said bits, means for reversing the order of the samples in a second segment in each pair in response to a fourth of said bits, and means for reversing the order of said first and second segments in each pair in response to a fifth of said bits.
-
-
25. A decoder for decoding a scrambled composite video signal which has been periodically sampled and comprises substantially continuous video segments separated by at least one video sample, said video signal having been scrambled by (1) inverting the polarity of the samples in selected segments, (2) reversing the order of the samples in selected segments, and (3) reversing the order of the segments in selected segment pairs, all in accordance with a predefined pseudorandom code, said decoder comprising the combination of
a pseudorandom number generator for generating a plurality of pseudorandom numbers for at least some of said video lines, each pseudorandom number having multiple bits, and video de-scrambling means responsive to said pseudorandom numbers for (1) restoring the polarity of the inverted samples in said video segments to the polarity of such samples in the original video segments, (2) restoring the order of the reversed-order samples in said video segments to the order of such samples in the original video segments, and (3) restoring the order of the reversed-order segments in said video data portion of said video lines to the order of such segments in the original video lines.
Specification