Image superimposing apparatus for superimposing the encoded color televison signal with the external composite video signal

Abstract

An external sync image superimposing apparatus synchronizing an analog video signal with digital image data is provided by an apparatus which includes a sync separator for separating an external composite sync signal from an external composite image signal, a clock signal generator for synchronizing the frequency of the clock signal with an external sync signal according to a phase difference between the horizontal sync signal of the separated external composite sync signal and the internal horizontal sync signal and generating the adjusted clock signal, a sync signal generator receiving the adjusted clock signal for generating an internal composite sync signal and a reproduction address signal, a video memory for reading stored digital video information according to the reproduction address signal and a superimposing circuit for converting the digital video information from the video memory into an RGB signal, encoding the internal composite sync signal and the RGB signal as a color television signal, and superimposing the encoded color television signal with the external composite image signal for output. The apparatus provides high screen quality without distortion, by synchronizing and superimposing the digital image signal onto the image signal.

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