Video encryption system
US4815129A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 2, 1985 |
| Grant date | Mar 21, 1989 |
| Priority date | — |
| Expiry date | Jan 2, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/1716
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An encrypted video distribution system includes a signal originating station which distributes television signals in a format unrecoverable by a standard television receiver. In particular, the normally occurring vertical and horizontal synchronizing pulses are deleted and, optionally also, video information is selectively inverted about a voltage reference potential intermediate the black and white levels. To permit synchronization restoration, a keying pulse is transmitted once each video field, and a synchronizing digital code burst transmitted once each frame--all at a fixed, predetermined intra-frame timed relationship. At each authorized subscriber location, the keying pulse and digital code burst are employed to lock a receiver frame clock which derivatively gives rise to all requisite reception-permitting synchronizing pulses. The transmitted information also contains information sufficient to restore the inverted video program content.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.