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Post by Pyrofer on Aug 16, 2019 16:01:48 GMT
Slowly making progress with this dedicated scandoubler hardware. At the moment one of the issues I don't like is you need to hook into the dotclock pin on the VDC (internal wire mod), but I think I can get around that with some pll stuff on the clock on my board. Anyway, Here is the output i.postimg.cc/KvFqF0bV/Scandoubler-Test-Card.jpgThats a photo of an LCD VGA monitor. I tried mode mania and it seems to work nicely, i.postimg.cc/MZQ92hQq/scandoubleroutput.jpgShown with the monitor info box so you can see it's converted to a VGA resolution And one last picture, I took this using an old VGA monitor from back in the 90s i.postimg.cc/DwQbhc2C/Scandoubleron-CRT.jpgAnyway, lots of progress being made.
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Post by tokra on Aug 16, 2019 18:07:15 GMT
This looks like just one of the interlace-fields of the Avril-image... could send you the original .ppm for verification.
Can you try cursor-up/down to see if that improves things? You can change the vertical sync (register 7) with that. I know that with my LCD-TV sometimes just ONE particular reg 7-settings shows both fields.
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Post by mirkosoft on Aug 16, 2019 19:17:11 GMT
Really good! If it fixes flickering - what is scandoubler (flicker fixer) function - it will solve my long time problem with CGA2VGA adapter. Please can you post source of VDC test picture? I know that it is possible by photo re-type it but it is not easy to do.
Thank you. Miro
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Post by Pyrofer on Aug 16, 2019 22:48:02 GMT
Tokra, I think I have an old/bugged version of the mode mania as sometimes it crashes or doesn't load images. I will try and get the latest one and redo the image. I have some more samples and thought it looked quite good myself! mirkosoft, the testcard app isn't mine I will ask the guy who wrote it if he doesn't mind me sharing it. (it's just polite). As far as "flicker fixer" it's not. Currently it does not de-interlace the image, the flickering can be quite bad. I have an idea on how to de-interlace and remove the flicker but it requires massive changes to the design and many many more components. As it is, with a non-interlace image there is no flicker In interlace mode. ugh. But it does flicker in VGA instead of PAL.
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Post by Pyrofer on Aug 18, 2019 0:26:52 GMT
Call for help! (NONE NEEDED! IT WAS MY MONITOR!) Ok. So, I had it mostly working except a slight drift, I adjusted my hsync timing and suddenly I get no picture. The monitor detects a signal (at least it doesn't say no signal) but no pixels are displayed. A scope shows that the output is, as far as I can see, perfect.
I have a suspicion it's to do with when the hsync pulse occurs in relation to vsync. I can find no specific data regarding how that should be treated however.Here you can see Vsync (top) and hsync (bottom) i.postimg.cc/h41Dv2Jx/C2-Hsync-out-C1-Vsync.jpgHere is a close up of Hsync (top) and pixel data (bottom). Note that there is no pixel data during the blanking period (this causes blank screen issues) i.postimg.cc/GhMbJ9xm/C2-pixel-data-C1-Hsync-out.jpgHere you can see a Vsync pulse (top) followed by pixel data (bottom), again, no data in the blanking period i.postimg.cc/1XBsdzxM/C2-pixel-data-C1-Vsync.jpgHere is a comparison of the input and output sync pulses. You can see the scandoubled output is exactly in sync with the original 15khz hsync pulses i.postimg.cc/7hwqX2Rf/C2-Hsync-in-C1-Hsync-out.jpgSo, if anybody knows anything about video sync timing, please help! The monitor in question not only doesn't display pixels but even the buttons stop functioning, as if its too busy to respond. It does however remain powered as if it's detecting a signal.
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Post by Pyrofer on Aug 19, 2019 13:45:17 GMT
Ok. So the scandoubler works. You get a pretty amazing picture, it's rock solid and looks great. I now have a choice. This design is a simple line doubler. It does not work with interlaced images. I have 3 options now,
1) Add a small bit to the design to enable it to show interlaced images and have a switch to fill in scanlines when not showing interlace 2) Redisgn as a full frame converter that takes two whole fields odd and even and converts them into one progressive true VGA de-interlaced image. 3) Leave as is.
There will be cost implications for each. Option one will riase the final price of the board a little. Option 2 doubles the component cost but gives the best output. Lastly, option 3 would be the cheapest final product price.
What are peoples feelings on this?
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Post by mirkosoft on Aug 19, 2019 14:50:32 GMT
My opinion is that best choice is 2. Allow to display interlaced modes in progressive scan to fix flickering, no matter of price. I'm using yet CGA to VGA converter which removes flickering, but it does it without intensity - it is not digital converter, it's analog. Robert Willie (aka Hydrophilic) integrated for me intensity, but there's no applicable dark yellow fix. Your solution is for me interesting and by your final choice, I buy it sure. Miro
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Post by tokra on Aug 19, 2019 15:37:29 GMT
Always go for best output quality while you're at it. No use in releasing an inferior product. So option 2 from me as well.
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Post by bjonte on Aug 19, 2019 20:03:43 GMT
Yep. It will be harder to justify buying the product if it isn’t both compatible and high quality. I’d rather pay more once than continuing to look for better options.
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Post by willymanilly on Aug 19, 2019 22:49:40 GMT
Option 2 from me as well for the reasons already mentioned by others.
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