Patent ID: 6356316
Filing Date: 2002-03-12
Classification: G09G,H04N

Abstract:
A method for merging a video display signal, such as that provided as an output from a microcomputer, with a raster scan video signal to form a composite video signal comprising:providing the raster scan video signal to an input video processor to obtain vertical drive synchronization, horizontal drive synchronization, and direct current restored video signal components; synchronizing the microcomputer video display output signal to the horizontal drive synchronization component and the vertical drive synchronization component of the raster scan video signal; merging the synchronized microcomputer video display output signal with the direct current restored video signal component of the raster scan video signal to form said composite video signal, said step of merging comprising the steps of: providing the synchronized microcomputer video display output signal as a first input to a keying circuit; providing the direct current restored video signal component of the raster scan video signal as a second input to the keying circuit; sensing the presence of input microcomputer video display signal; forming said composite video signal as the output of the keying circuit by causing the output of the keying circuit to be switched to the synchronized microcomputer video display output signal whenever the synchronized microcomputer video display output signal is present; and switching the keying circuit to the direct current restored video signal component of the raster scan video signal whenever the synchronized microcomputer video display output signal is not present.