Capturing Old IBM CGA Video - Taming the Beast
0The old-style IBM CGA card's composite video output isn't very friendly to modern display and capture devices. When you try to capture it, the output is tends to show crooked horizontal lines, wavy interference patterns and will even will cause some screens to lose sync and fail to display at all.
In the first part of this video, I show the basic capture of the old-style video signal. When I try to enter the help screen, my capture device cannot display the screen, so you see a solid blue screen. The inventory screen is off-center so much that some of the text is missing.
One solution to this problem is to use a Y-adapter plug to plug the video into another device. In this case, at 1:05, I plugged the other end of the Y-adapter into my TV. As if by magic, almost all the problems disappear and the game can be viewed without all the artifacts.
A standard RCA composite video signal outputs at 1v peak to peak, but old IBM CGA outputs at 1.5v peak to peak. This "hotter" signal was much better tolerated by the displays of the early 1980s than the mid-2000s or later.
New-style IBM CGA cards are much better behaved and will show these graphics without the need for the splitter. They output at a standard 1v peak to peak.
Another solution is to bridge a resistor, no more than 75ohms, between video and ground. That will drop the voltage sufficiently to eliminate old-style CGA hot video issues.