Scrambled television signals
US4727579A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 11, 1984 |
| Grant date | Feb 23, 1988 |
| Priority date | — |
| Expiry date | May 11, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/1675
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A television receiver for receiving scrambled television signals has an arrangement (3) which provides scrambled video components (V) and packet arranged sound/data components (D) some of which are also scrambled. The components (D) are applied to a packet demultiplexer (4) where the packets are assembled from the data in several lines in the signal to provide at a first output (P), the respective packets carrying sound/data information and, at a second output (E), encrypted control data which is applied to a sub-system (6) to produce a video scrambling control word (VS) for each line of the video components. The sub-system (6) during each line produces further bits which are applied to a descrambling control word generator (7) which assembles these further bits from three lines to form a packet scrambling control word. This control word and the packets associated with it are added in an adder (5) and applied to a main packet buffer store (8) from which each packet is read out by a packet selector (9), and the packet is applied to a packet descrambler (12) while the packet scrambling control word is selected by a register (11) and used to control the generation of a binary sequence…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.