Television signal encryption system with protected audio
First Claim
1. In combination in a system for communicating a television program which includes encrypted audio and video signals;
- signal originating means including a first pseudo random generator for generating an audio scrambling control signal, means for generating polarity inverted and non-inverted versions of the television audio signal, and selection means controlled by said first controlling means for operatively selecting for communication the polarity inverted or the non-inverted version of the television audio signal; and
receier means including means for receiving the signal supplied by said selection means, said receiver means including a second pseudo random generator for generating a replica of said udio scrambling control signal, means for generating polarity inverted and non-inverted versions of the signal received by said receiving means, and additional selection means controlled by said second controlling means for operatively selecting for listening said inverted or non-inverted version of said received audio signal, whereby the output of said additional selection means comprises polarity restored audio, said signal originating means further 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 video inversion means, and means for distributing a measure of said inversion reference level with the composite signal distributed by said signal distribution means; and
wherein said receiver means further includes means for receiving said composite signal from said signal distribution means;
said decrypting means including inversion reference means for recovering the received video 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 the audio portion of outgoing television program-bearing signals. In particular, the audio content of a television program alternately reverses polarity under control of a keyed pseudo random generator. At each authorized subscriber location, a pseudo random generator is included in receiver descrambling circuitry and operates in a sequence identical to the like circuit at the head end to restore the polarity-inverted audio signal, thereby permitting reception and presentation of intelligible audio subject matter.
In accordance with another aspect of the present invention, the video information present during selected lines is inverted about a predetermined inversion level and restored at equipped, authorized subscriber stations also under control of the pseudo random generators.
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Citations
12 Claims
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1. In combination in a system for communicating a television program which includes encrypted audio and video signals;
- signal originating means including a first pseudo random generator for generating an audio scrambling control signal, means for generating polarity inverted and non-inverted versions of the television audio signal, and selection means controlled by said first controlling means for operatively selecting for communication the polarity inverted or the non-inverted version of the television audio signal; and
receier means including means for receiving the signal supplied by said selection means, said receiver means including a second pseudo random generator for generating a replica of said udio scrambling control signal, means for generating polarity inverted and non-inverted versions of the signal received by said receiving means, and additional selection means controlled by said second controlling means for operatively selecting for listening said inverted or non-inverted version of said received audio signal, whereby the output of said additional selection means comprises polarity restored audio, said signal originating means further 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 video inversion means, and means for distributing a measure of said inversion reference level with the composite signal distributed by said signal distribution means; and
wherein said receiver means further includes means for receiving said composite signal from said signal distribution means;
said decrypting means including inversion reference means for recovering the received video 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)
- signal originating means including a first pseudo random generator for generating an audio scrambling control signal, means for generating polarity inverted and non-inverted versions of the television audio signal, and selection means controlled by said first controlling means for operatively selecting for communication the polarity inverted or the non-inverted version of the television audio signal; and
Specification