Video encryption system
First Claim
1. In combination in a scrambled composite video signal distribution system;
- signal originating encrypting means including selective inversion means for selectively inverting the video information content of video lines about an inversion reference level and for not inverting the video information content of other lines, signal distribution means for distributing the output signal produced by said selective inversion means, and means for distributing a measure of said inversion reference level with the composite video signal distributed by said signal distribution means; and
signal recovering decrypting means for receiving said composite video signal from said signal distribution means, said decrypting means including inversion reference means for recovering the received inversion reference level, and means for selectively reinverting the video information content of inverted video lines about the recovered inversion reference of said inversion reference means.
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Accused Products
Abstract
An encrypted video distribution system includes a signal-originating head end for scrambling outgoing television program-bearing signals. In particular, the video content of selected lines is inverted about a reference voltage level, and the inversion reference level amplitude transmitted in pulse form during the horizontal synchronizing pulse interval. Line video inversion/non-inversion is controlled by a keyed pseudo random generator.
At each authorized subscriber location, all inverted lines are restored to proper format, using the accompanying received inversion amplitude level present during horizontal sync as a reference. A pseudo random generator is included in the receiver descrambling circuitry and operates in a sequence identical to the like circuit at the head end to identify those lines requiring video inversion.
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Citations
20 Claims
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1. In combination in a scrambled composite video signal distribution system;
- signal originating encrypting means including selective inversion means for selectively inverting the video information content of video lines about an inversion reference level and for not inverting the video information content of other lines, signal distribution means for distributing the output signal produced by said selective inversion means, and means for distributing a measure of said inversion reference level with the composite video signal distributed by said signal distribution means; and
signal recovering decrypting means for receiving said composite video signal from said signal distribution means, said decrypting means including inversion reference means for recovering the received inversion reference level, and means for selectively reinverting the video information content of inverted video lines about the recovered inversion reference of said inversion reference means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
- signal originating encrypting means including selective inversion means for selectively inverting the video information content of video lines about an inversion reference level and for not inverting the video information content of other lines, signal distribution means for distributing the output signal produced by said selective inversion means, and means for distributing a measure of said inversion reference level with the composite video signal distributed by said signal distribution means; and
- 16. In combination in receiver means for receiving encrypted video signals comprising an inversion reference level signalling pulse, and video information selection transmitted either without inversion or inverted about the inversion reference level embodied in said inversion reference level pulse, said selective inversion being dictated by an operative inversion sequence, said receiver means including means for producing non-inverted and reinverted replicas of received video information, said reinverted replica producing means including inverting difference amplifier means responsive to the difference between the received video and the received reference level signalling pulse, first and second switch means having inputs supplied with said non-inverted and reinverted video information replicas and combined outputs, and control means generating said operative inversion sequence for controlling said first and second switches.
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19. Descrambler apparatus for descrambling an encrypted video signal, said video signal being encrypted by inversion of selected video lines about an inversion reference level, said video signal further including a signal representative of said inversion reference level, said descrambler apparatus comprising inversion reference level storage means responsive to said video signal for providing a signal output representative of said inversion reference level signal contained in said receied video signal;
- and inversion amplifier means for inverting said selected video lines of said video signal, said inversion amplifier means coupled to said output signal from said reference level storage means for inverting said selected video lines about said stored inversion level reference signal.
- View Dependent Claims (20)
Specification