Method and apparatus for improving video scrambling and employing split sync pulses
US5142575A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 2, 1989 |
| Grant date | Aug 25, 1992 |
| Priority date | — |
| Expiry date | Nov 2, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/1713
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
This invention discloses a new and improved method of scrambling video signals by inversion of the video information by splitting the sync pulse into plural portions and transmitting each portion of the sync pulse at a predetermined level. This improves the quality of the recovered video compared with other video inversion systems by rendering the video less sensitive to variations in the modulation depth of the modulator carrying the inverted signal, the demodulation sensitivity of the demodulator and the stability of the recovery circuits. The invention further provides additional security against pirating by allowing the scrambling circuit to operate in diverse modes, each of which will cause a TV to react differently should a conventional pirating device be employed. The invention also renders the signal capable of being transmitted with unmodified modulators of the type normally employed in the CATV industry.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.