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Post by tokra on Dec 13, 2019 15:24:36 GMT
Maybe it is because of the "+1"-rule the VDC-chip applies to some registers? The C128 PRG says:
"R7 VERTICAL SYNC POSITION The number of character rows, plus 1, from the first displayed character row to the start of the vertical sync pulse. This number should be greater than the number in R6 (vertical displayed)."
For some reason the C128 PRG is mostly correct (apart from register 5...)
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Post by tokra on Dec 13, 2019 15:21:35 GMT
At least the C128 Programmer's reference guide tells you as much:
"In the pixel double-width mode, the value written to R22(3-0) should be 1 larger than the numbers described above."
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Post by tokra on Dec 13, 2019 15:16:51 GMT
Yes, for some reason or other register 5 needs to be increased by one. This is what I found out doing my VDC Mode Mania back then and IIRC by analysing Graphic Booster and the old "64er Sonderheft 29".
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Post by tokra on Oct 6, 2019 11:38:43 GMT
Does the image already fit the restrictions of the color-map? E.g. just two colors per 8x2 block? Then you would need to go 8x2-block by 8x2-block to decide which is the background color of the block (and set the according pixels to 0) and which is the foreground color (and set the according pixels to 1). Then you have your black&white-bitmap. Then you re-apply the colours in your colour-map for each block and voila!
The converters from VDC Mode Mania were done by Mike and they acutally take a true-color-PPM-file and apply ditheirng to get the best color-result. They are part of the ZIP-archive of Mode Mania under the directory converters. Mike likes to keep the sources to these private however. For your task of converting a given image that already fits the restrictions these will not work. But it should be possible to write a small BASIC-program to do the job.
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Post by tokra on Sept 22, 2019 19:22:43 GMT
Can't see anything terribly wrong with it. If you aim for NTSC you should go for 126 in reg 0 and 131 in reg 4 (131+1)*2 = 264 as that matches Commodore's original settings from the NTSC-ROM. For bitmap-mode (reg 25 = 199) you do not need to set reg 23, this is for text-mode only I think. reg 7 (vertical sync) is something you need to play around with a little sometimes. 128 should be correct, you use 116?
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Post by tokra on Sept 13, 2019 8:53:32 GMT
Ah, I see, I knew that of course ;-) The original formula was posted some years ago by hydrophilic if IIRC. I used that to adjust my VDC Mode Mania modes to be close to PAL or NTSC.
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Post by tokra on Sept 12, 2019 14:40:59 GMT
What is this "SinglePixelMode" you are speaking of?
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Post by tokra on Sept 4, 2019 8:18:11 GMT
I experimented with this in 2013, please see attached. Can't remember what I did there, just check the source-code. I know that the character-definitions in the ibmfont-file do not match the position they need to be in the Commodore-setup. So for this to work properly you would need to map each character to the correct place in RAM. At least this is a start Attachments:vdcdosfont.d64 (170.75 KB)
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Post by tokra on Aug 20, 2019 15:33:19 GMT
Well, even the monitors of the past could not display all modes. For example most 1901s cannot display 400 vertcial lines (800 interlace) and cannot be adjusted for horizontal width, which means about 720 pixels is the visible maximum horizontally. The 1084 cannot display much more than 300 vertical lines (600 interlace) but can go wider horiztonally and display 800x600.
And then the crazy-modes of VGA-mode-mania only work on 31.5kHz-monitors.
So it will be near-impossible to build a device that can display every theoretical mode.
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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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