Bts Broadcast Television Systems Gmbh

Peter Bachmann

Dieter Poetsch

Mike Christmann

Dieter Schmidt

Memories are provided for correction signal values respectively for a hue signal, a saturation signal and a luminance signal derived from a digital color television signal. Each of the memories consists of two memory units which are alternately used for storing new correction signal values and for reading out previously stored correction signal values. The corrected signal values are modified by a key signal, if present, in each case and are then supplied to calculation circuits to each of which a signal derived from the saturation signal is applied. The resulting fully corrected hue and saturation signals are converted back into color difference signals, but the finally corrected luminance signal requires no conversion. The raw correction signal values are supplied from a computer into which control magnitudes can be entered to produce them. These control magnitudes can be used to define corner points of a deflected line function from which the correction signals are derived. Monitors and cursors are used to facilitate correct entry of control magnitudes.

Video signal color correction based on color hue

Memories are provided for correction signal values respectively for a hue signal, a saturation signal and a luminance signal derived from a digital color television signal. Each of the memories consists of two memory units which are alternately used for storing new correction signal values and for reading out previously stored correction signal values. The corrected signal values are modified by a key signal, if present, in each case and are then supplied to calculation circuits to each of which a signal derived from the saturation signal is applied. The resulting fully corrected hue and saturation signals are converted back into color difference signals, but the finally corrected luminance signal requires no conversion. The correction signal values are supplied from a computer into which control magnitudes can be entered to produce them. These control magnitudes can be used to define corner points of a deflected line function from which the raw correction signals are derived. Monitors and cursors are used to facilitate correct entry of control magnitudes.

Video signal color correction with dual function memories and color

A digital color television signal has its chrominance component, which is in the form of color difference signals, resolved into color hue and color saturation signals which are used to address a function memory which provides a pair of correction signals that are supplied to calculator circuits which respectively receive the color hue signal, the color saturation signal and the luminance signal as well as predetermined control signals previously stored which relate to the color sectors adjacent to the color sector in which the color hue signal is located. The calculation circuits respectively supply corrected color hue, color saturation and luminance signals. The color hue signal is additively corrected by a color hue correction signal and the color saturation signal is multiplicatively corrected by a saturation correction signal.

Video hue correction taking account of saturation and luminance

For picture elements (pixels) having a luminance value in a mid-range of luminance magnitude and a color saturation smaller than a predetermined threshold value a correction signal is obtained by integration of the color saturation value followed by multiplication by the difference between an actual luminance signal and a gradation distorted luminance signal. Threshold values at the boundaries of the mid-range of the luminance signal are determined in a manner dependent upon the extreme values that appear from time to time in the luminance signal. The stored maximum and minimum values of the luminance signals are respectively decremented and incremented at frame intervals until replaced by a new maximum or minimum value establishing a new maximum or minimum.

Growing community of inventors

Aschaffenburg, Germany

Peter Bachmann