System for two-dimensional blending of transitions between a col

Details System for two-dimensional blending of transitions between a col System for two-dimensional blending of transitions between a col

1987-03-19

1989-05-23

Groody, James J.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358325, H04N 975

Patent

active

048335240

ABSTRACT:
The magnitude of a chroma-key selected color signal is evaluated for successive pixels in comparison with the previous line as well as in comparison with a previous pixel, for processing a cutover switching signal. A provisional switching signal is produced if either comparison result exceeds a prescribed threshold value. Since it is desired to fade in the foreground signal, it becomes important, if the trailing edge of the provisional signal occurs relatively early, that an adaptive nonrecursive digital filter operating as a color carrier phase shifter should be used to assure prompt transfer of control of the fading in (or fading out) steps to a color carrier phase correction signal present at the input of an intermediate store which operates as a sample and hold circuit. The filter receives successive color control signals for a period controlled by an exclusive OR-gate comparing the delayed and an undelayed provisional switching signal. For providing this operation in both picture dimensions, exclusive-OR gates (8, 9) respectively correlated with pixel and line interval delays are used to control the horizontal (16) and vertical (17) sample and hold circuits which in turn provide color carrier phase correction signals to respective horizontal (18) and vertical (19) nonrecursive filters. The provisional switching signal (S.sub.d) is used to produce color corrected switching control signals (S.sub.xy) by the processing of the vertical filter (19) followed by the processing of the horizontal filter (20).

REFERENCES:
patent: 4365308 (1982-12-01), Heitmann
patent: 4403245 (1983-09-01), Wischermann

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