Dynamic range video black level expander

Details Dynamic range video black level expander Dynamic range video black level expander

1989-03-31

1990-12-04

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358164, 358168, H04N 514

Patent

active

049757733

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.

REFERENCES:
patent: 4187519 (1980-02-01), Vitols et al.
patent: 4204229 (1980-05-01), Hevze
patent: 4470067 (1984-09-01), Mino
patent: 4654710 (1987-03-01), Richard
patent: 4712132 (1987-12-01), Soca

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