Re: RGB to Component video converter (SCART)

Charlie wrote:
"Michael J. Mahon" <mjmahon@xxxxxxx> wrote in message news:NpOdna707f6llNzbnZ2dnUVZ_qOpnZ2d@xxxxxxxxxxxxxx

Charlie wrote:

"Michael J. Mahon" <mjmahon@xxxxxxx> wrote in message news:V5adnbcn4JDnGKLbnZ2dnUVZ_revnZ2d@xxxxxxxxxxxxxx


Charlie wrote:

As it stands now I get a usable but not perfect picture. The only problem seems to be in the transition from one color to another horizontally. For instance, if you have a line of horizontal black pixels which turn to white there will be one pixel at the transition that is gray. This creates a horizontal ghosting effect that can be reduced by judicious adjusting of the contrast and sharpness, but some color combinations are worse than others. I had the impression from past threads that this ghosting effect was caused by the monitor not being able to sync with the IIgs signal frequency.

I presume you are using a digital monitor,


Yes, it is a combination 1440x900 (19" wide screen) LCD monitor and HD TV with just about every type of video input.



and you are correct, the
"intermediate" value pixel is the result of the sampling clock of the
monitor not being locked to the dot clock of the IIgs. If the pattern
of gray pixels is constant and consistent over the width of the display,
then your monitor may have locked to a multiple of the dot clock.




Yes, the pattern is constant and consistent over the width of the display. I do want to make clear that this pattern is not very bad (at least to my eye). Its better than the fuzziness of my failing IIgs monitor and the picture is a lot bigger which is better for my failing eyes.

You might want to check the monitor's menus for an "Image Lock" or
similar submenu that would allow you to manually try to get a better
sampling clock lock than the automatic mode is accomplishing.



Thanks for the tip Michael. I took a close look at the monitor menu and it indeed had an "Image Lock" submenu. Then reality set in. That menu is unavailable when using the SCART input. I have no idea why. The documentation just says "Available in PC mode only".

I think of it as a kind of paternalism. ;-(

They know that PC video uses a variety of pixel clocks, but monitor
designers often seem to think that RGB input has only a few different
"standard" clock possibilities. It would be trivial to provide sampling
clock adjustment in all modes.

-michael

NadaNet file server for Apple II computers!
Home page: http://members.aol.com/MJMahon/

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