| 摘要 |
<p>VIDEO ENCRYPTION SYSTEM 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.</p> |
