Dynamic range video black level expander
US4975773A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 31, 1989 |
| Grant date | Dec 4, 1990 |
| Priority date | — |
| Expiry date | Mar 31, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/57
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A digital video signal black level expander in which the dynamic range of the video signal is the criterion for expansion. The digital video signal is compared pixel by pixel in maximum and minimum comparators and the maximum and minimum pixel values for each field are stored in latches. Integrators average the maximum and minimum pixel values over successive pairs of fields of the video signal. The integrated minimum pixel value is subtracted from the integrated maximum pixel value to determine the dynamic range of the pixels in the video signal. A tilt-point pixel value is established as a function of the dynamic range, above which no expansion is permitted. Digital video signals below the tilt point are expanded. Programmable constants are supplied to modify the dynamic range effect and the amount of expansion as desired. A low pass filter removes high frequencies prior to comparing pixel values.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.