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Re: PC/XT/AT (inside) WIP topic [Re: Kale] #102104 10/19/15 11:29 PM
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crazyc Offline
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With our current hlsl ntsc shader I get this somewhat better output.

With some more tweaking of the initial angle, the colors could probably be a bit better.

Re: PC/XT/AT (inside) WIP topic [Re: Kale] #102106 10/20/15 02:49 AM
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mixmaster Offline
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Nice job with the HLSL shader, the colors seem to be far from proper though.

Re: PC/XT/AT (inside) WIP topic [Re: crazyc] #102110 10/20/15 04:22 AM
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Originally Posted By crazyc

With some more tweaking of the initial angle, the colors could probably be a bit better.


"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"
Re: PC/XT/AT (inside) WIP topic [Re: crazyc] #102116 10/20/15 03:01 PM
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reenigne Online Content
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Originally Posted By crazyc
With our current hlsl ntsc shader I get this somewhat better output.


Very nice!

Originally Posted By crazyc
With some more tweaking of the initial angle, the colors could probably be a bit better.


Adjusting the hue (and the phase of the pixel grid relative to the colour burst) will only get you so far. To accurately reproduce the colours you get from doing CGA composite artifacting with arbitrary direct colours, you will need to take into account the analogue behaviour of the CGA's chroma multiplexer chip (it's a digital chip, but for these colours the analogue characteristics matter).

One way to do this (the best one I've found) is to generate the output signal from this chip sample by sample (at a sample rate of 14.318MHz). Each output sample depends on three things: the direct colour of the (14.318MHz) pixel, the direct colour of the previous pixel and the phase (of the four possible pixel phases relative to the colour burst). Then the multiplexer behaviour can be completely characterized by a 256 element table (8 colours for current pixel times 8 colours for previous pixel times 4 phases).

I've made some careful measurements of the output from my CGA to populate this table (a bit like dumping a ROM, but analogue instead of digital). The table (and algorithm) can be found in the patch I made for DOSBox (latest version is at http://www.vogons.org/viewtopic.php?f=41&t=12319&start=640#p431721) or (if you'd prefer to avoid patches to GPLed code) on my github at https://github.com/reenigne/reenigne/blob/master/8088/cga/calibrate/cga2ntsc/cga2ntsc.cpp (all the code there is released under UNLICENSE so can be re-released under whatever license you like).

To get the final composite output, you need a weighted sum of the chroma multiplexer output and the intensity bit. For new CGA you also need a weighted sum of the red, green and blue bits as well. A nice thing about using a 256 element table instead of a 1024 element table is that the same table can be used for both old and new CGA. You can see the weightings in both the links above.

Feel free to ask me any questions about this code - I'm happy to help add it to any emulator that wants it (although it's a long time since I've touched the MAME/MESS source).

Re: PC/XT/AT (inside) WIP topic [Re: R. Belmont] #102119 10/20/15 04:56 PM
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Originally Posted By R. Belmont
My proposal for the BGFX universal renderer (which I'd love to see JD to get drunk and spit out some detailed ideas for) includes the possibility of drivers forcing shaders from a canned library, like "NTSC".


If you want to experiment on the api side, remember that I do have a pure software ntsc decoder in a corner.

OG.

Re: PC/XT/AT (inside) WIP topic [Re: Olivier Galibert] #102120 10/20/15 05:07 PM
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Originally Posted By Olivier Galibert
Originally Posted By R. Belmont
My proposal for the BGFX universal renderer (which I'd love to see JD to get drunk and spit out some detailed ideas for) includes the possibility of drivers forcing shaders from a canned library, like "NTSC".


If you want to experiment on the api side, remember that I do have a pure software ntsc decoder in a corner.


I even managed to find the corner.

http://og.kervella.org/ntsc-decoder.zip

Compile with gcc -O9 -Wall -g ntsc-lb-1d.c -o ntsc -lm -lz, generate the image with ./ntsc 00925.bin 00925.png.

Expects a 13.5Mhz 8-bit composite signal. I can trivially generate filters for other frequencies. The code that does it is gpl, but of course reimplementable if needed.

OG.

Re: PC/XT/AT (inside) WIP topic [Re: Kale] #102300 10/28/15 10:54 PM
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Still Sicomp PC16-05:
More pictures - rear side of the memory card and closeups of the Floppy/Serial/RTC card plus a different bootdisk (created just seconds before the HD packed in :-/ ) with the original autoexec.bat/config.sys that show the settings for the current configuration of the memory card.

https://dl.dropboxusercontent.com/u/55419307/Siemens%20Sicomp%20PC16-05.rar


NCR DMV- DEC Rainbow- Siemens PCD- ITT 3030-Oly People- Acorn A5000- Olivetti M20
Re: PC/XT/AT (inside) WIP topic [Re: Kale] #104604 03/18/16 02:54 AM
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It works better when the ROMs are mapped properly.

Yes, it's arcade hardware but at486 based.

Re: PC/XT/AT (inside) WIP topic [Re: Olivier Galibert] #104612 03/18/16 06:38 PM
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Originally Posted By Olivier Galibert
If you want to experiment on the api side, remember that I do have a pure software ntsc decoder in a corner.


Bonus points if you can overlay artwork over the ntsc monitor. Ideally monitors would be devices and you could plug different ones in.

Re: PC/XT/AT (inside) WIP topic [Re: Kale] #104656 03/21/16 02:37 PM
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crazyc Offline
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Another AT based "arcade" (probably really only in bars) machine.

Skipped the protected here too. I also had to replace the VGA bios to get this far. The game expects to be able to set 640x480x8bpp mode but the bios doesn't support it and there's no VESA extension anywhere. It appears to be a bios for a standard 256KB card. If someone knows where one of these machines are it'd be helpful to dump the vga card rom again.

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