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"Hard Hat Mack" on Atari XL was likely also supposed to do NTSC artifact colours. On my PAL TV it only made an ugly fuzzy B/W texture with blue/yellow flickering hue instead of recognizable colours.


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Originally Posted by ICEknight
Wouldn't having MAME always render the full uncropped video output (with the aspect ratio corrected) allow for always sending it the same texture size, for systems that share aspect ratio?

Vertically yes, but horizontally the texture width really depends on the pixel clock and that varies.

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In "Zybex" on Atari 800XL there is a flickering line to the left of the screen, and the POKEY music is missing the bass voice! (It happens both in PAL and NTSC Atari, only in NTSC the music plays faster.)

This is what the music should sound like on NTSC (written for PAL, it is originally slower).


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Are there in fact any values known for the artifacting of the Ataris via HLSL/BGFX similar to the Apple II? Or is something to be found out or confirmed to be not possible yet?

Last edited by Reuental; 03/23/22 02:14 PM.
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I have no idea. I would lean towards "it probably doesn't work" but I don't think anyone's tried either.

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There's no reason why it won't work if you can make the Atari driver output pure monochrome, and can manually calculate the necessary values to plug in for the Atari vs. the default NES setup that the default parameters have, same as how other people have calculated the same for the Apple II series.

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Originally Posted by Golden Child
so far I've found that

Choplifter
david's midnight magic
lode runner
diamond mine
Ultima IV

use the artifact colors

Aztec's title page might, too. It does for sure on the Apple II.

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I got interested in fiddling with the NTSC HLSL filter with CGA on the ibm 5150.

It's sort of discouraging to fiddle with since it's very slow on my systems (probably needs a powerful video card). I can speed it up a bit by making the window smaller and setting the frameskip to 10/10.

A little GWBASIC program to make some patterns in 640x200 resolution:

start the ibm5150 with pcdos2 and launch gwbasic with "gwbasic"

Code
90 SCREEN 2 : CLS
100 FOR C=0 TO 15: FOR X=0 TO 150: BAR=10:FOR Y = C*BAR TO (C+1)*BAR: GOSUB 900 :NEXT:NEXT:NEXT
200 LOCATE 20 : END
900 PX0 = X * 4 : FOR PX = PX0 TO PX0+3
910 O = PX - PX0 : PXC = C AND (2^(3-O)) : PSET(PX,Y),(PXC<>0)* -1 : NEXT : RETURN


running this gets you this screen:

[Linked Image from i.imgur.com][Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com][Linked Image from i.imgur.com]

compare to the cga artifact colors given at https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-illustrated/

and they are the same colors as the apple ii lo-res colors pattern of 0,4 2,6 1,5 3,7 8,12 10,14 9,13 11,15. (and the same as apple ii double hi-res)

[Linked Image from i.imgur.com]

ntsc a = 0.0
ntsc b = 1.0
scanline duration = 44.7
phase offset = 0.76


running this with Donald Duck's playground:

[Linked Image from i.imgur.com]

Interesting comparisons between the different versions of DDPG at http://frgcb.blogspot.com/2014/04/donald-ducks-playground-us-goldsierra.html

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Fiddling with the coco2 driver and DDPG:

setting Artifacts to none:

[Linked Image from i.imgur.com]

little bit brighter setting shadow mask to white:
[Linked Image from i.imgur.com]
[Linked Image from i.imgur.com]

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Okay, so let's try a800 lode runner:

default filter none with artifacts off:

[Linked Image from i.imgur.com]

bgfx filter HLSL NTSC and setting scanline duration to 46.9 usec

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

and tweaking the carrier a little to match the scanline length makes for more uniform color

If there were another settting to fine adjust the scanline duration with more precision (like .001 usec) that would work also

[Linked Image from i.imgur.com]

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