Method for preventing the deterioration of picture quality in a video processor and circuit thereof
US5353066A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 5, 1993 |
| Grant date | Oct 4, 1994 |
| Priority date | — |
| Expiry date | Nov 5, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/70
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and circuit for preventing the deterioration of picture quality in a video processor is disclosed in which, when an input color video signal is input, a clock signal for a combfilter is locked with a phase-locked loop (PLL) by a burst signal and when a monochrome video signal without the burst signal is input, the clock signal is locked by the output (quasi-burst signal) of a voltage-controlled oscillator of the PLL circuit, before the lapse of one horizontal period, so that the clock signal is constantly locked by a multiple (4 fsc) of the burst signal regardless of the presence or absence of the burst signal of the input video signal. According to a color/mono signal discriminating result, either the burst signal or the quasi-burst signal is selected as a reference signal so that the reference signal is locked to provide a clock signal having a constant phase and frequency, thereby preventing aliasing due to clock variations when the monochrome signal is input and thus improving picture quality.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.