| 摘要 |
An apparatus for showing a digitized NTSC-encoded video signal on an NTSC or PAL color television screen includes a system memory unit for storing the digitized video signal therein. A sync generator provides NTSC or PAL horizontal and vertical sync signals depending upon the type of color television screen in use. A sync delay and shading circuit provides an appropriate delay to the PAL horizontal and vertical sync signals when a PAL color television screen is in use. The horizontal and vertical sync signals control the cathode ray tube (CRT) unit to access the digitized video image in the system memory unit. The sync delay and shading circuit also disables the CRT control unit, a color burst generator, a (B-Y) and an (R-Y) color difference digital-to-analog (D/A) converter and a luminance and sync D/A converter during a 100 scan line period in which no video image is being displayed when the PAL color television screen is in use. The resulting effect is that a shaded region corresponding to 50 scan lines can be seen on the top and bottom portions of the PAL color television screen. Furthermore, a 0.5 microseconds blank in the horizontal direction is almost equally distributed on the left and right sides of the PAL color television screen. This minimizes the occurrence of distorted images and can thus provide a better viewing effect.
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