Method and apparatus for preventing the copying of a video program
US4907093A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 1, 1988 |
| Grant date | Mar 6, 1990 |
| Priority date | — |
| Expiry date | Nov 1, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2005/91314
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A video signal is modified so that a television receiver will still provide a normal color picture but which a video tape recorder will detect and prohibit its being recorded. A plurality of ordered pairs of pseudo-sync and positive pulses are added to the video signal vertical blanking interval following the normal sync pulse. A disabiling circuit associated with a recorder detects the modified signal. This detection may be by comparing the voltage differential between the pseudo-sync pulse tip and the positive pulse relative to the normal voltage differential between the sync pulse tip and the back porch of the blanking interval. Alternatively, the modified signal can be detected by identifying the pulse frequency of the signal in the blanking interval. A high frequency is indicative of the presence of the modified signal. Detection is also shown by peak-detecting the video signal and sampling this peak-detected signal during the vertical blanking period. A control signal is produced, when the modified signal is present, which disables the recording device. If no modified signal is detected, the recording device is enabled.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.