Graphic video overlay system providing stable computer graphics

Details Graphic video overlay system providing stable computer graphics Graphic video overlay system providing stable computer graphics

1984-04-12

1986-04-01

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358149, 358 17, 358903, 340814, H04N 504, H04N 944, G09G 300

Patent

active

045801657

ABSTRACT:
A color graphic overlay system for providing high speed, high resolution color graphics display combined with a video image from a videodisc, videotape or camera. The system includes a video mixing module and a color graphics module which generates the graphics while the video mixing module performs the overlay function. A composite sync processor filters an external video composite sync signal to produce a processed horizontal sync pulse that is phase adjustable and ultimately used by a phase lock loop to lock the horizontal component of the external video composite sync signal to the horizontal component of the graphics composite sync. The phase lock loop employs the processed horizontal sync pulse to generate a high frequency clock used by the color graphics module to produce its own horizontal sync pulses. Horizontal synchronization means provide a phase adjustable window which regulates the phase lock loop to eliminate the unstable effects of gross phase differences of external video by slowly time sliding the processed horizontal sync pulse to extend or reduce its period until the phase lock loop can compensate therefor.

REFERENCES:
patent: 4025951 (1977-05-01), Eckenbrecht
patent: 4346407 (1982-08-01), Baer et al.
patent: 4425581 (1984-01-01), Schweppe et al.
patent: 4450442 (1984-05-01), Tanaka
patent: 4498103 (1985-02-01), Aschwarden
patent: 4531154 (1985-07-01), Hallock

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