Hi! As many people already know, C64 is older than the consumer S-video signal format, and doesen't comply completely to that standard. The result is that if you make an adaptor from C64 to a S-video input the luminance will be slightly more to the left than the chrominance. If you on the other hand feed a S-video signal to an old Commodore CRT monitor the opposite will happend, i.e. luminance slightly to the right of the chrominance. Is the exact timing of this some kind of known fact, or is it still something that needs to be calculated or measured? Some 15-20 years ago I modified a CRT TV set to give correct picture both with a standard S-video source (i.e. CD32) and with a C64, using a thumb wheel switch to select one of the 8 possible different delays in a TDA4565 IC that were used in that TV. I don't remember which setting I used with C64 and with CD32 though. I see four approaches: 1: Compare the schematics of some TV sets with S-video input to the schematics of a Commodore CRT monitor with "C64 S-video" input, and figure out the difference 2: Find some spec on S-video timing. I've googled but haven't found anything. 3: Measure colour bars from a C64 and a known S-video source (for example CD32) 4: Extrapolate from looking at a picture (the mistiming seems to be approximately 2 pixels, so two cycles of the pixel clock would be about the mistiming) 5: Experiment with different delays. My idea is to figure out the optimal delay and then just calculate what cable length gives such delay (afaik it depends on what kind of insulation the cable uses so maybe a few different lengths could be calculated for different common types of 75 ohm coax cable). Then anyone who wants a perfect picture could just route the luminance through a cable of the correct lenght. If I'm not mistaken it would probably be a cable lengt of about 30 metres (100 feet) +/- 50% or so. That seems like a rather long cable but it's not that bad to hide under a desk or behind a TV. The point is that it would be a simple thing anyone with a soldering iron could do, without any need for some fancy electronics. Just pick up a spool of enough tv antenna coax cable and solder it in, and get a real picture improvement. IIRC the picture with a correct delay and a TV/monitor with CTI (Colour Transient Improvement, or some similar function) looks just as good as with a RGB signal. (For signals with higher resolution, like 640 pixels wide on CD32, anything that is only one pixel wide will be black and white, otherwise that will also look as good as a RGB signal). -- (\_/) Copy the bunny to your mails to help (O.o) him achieve world domination. (> <) Come join the dark side. /_|_\ We have cookies. Message was sent through the cbm-hackers mailing listReceived on 2017-08-31 19:00:08
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