Oddball Mode X Resolution Support \ VOGONS

Oddball Mode X Resolution Support

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First post, by kolano

Posted on 2014-02-20, 22:38

kolano Offline

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I'm trying to better understand how DOSBox handles oddball Mode X VGA resolutions. My current reference point is the eyecandy program Dial8, which supports 19 of them. I've noticed modes with more vertical lines than horizontal output a bit oddly in DOSBox's Windowed/Original mode/screenshots captured with DOSBox...

Some modes are output with doubled horizontal resolution. For instance 320x480 is output as 640x480, 320x400 is output as 640x400. I presume this is related to the pixels being fairly rectangular in those VGA modes and DOSBox trying to maintain the appropriate aspect ratio (even though I have aspect ratio correction off). More troubling some modes seem to omit half the vertical resolution. For instance 376x564 is output as 376x228.

Is there any way to support the 376x564 resolution properly (i.e. not halving it's vertical resolution)? I'm OK if that means 752x564.

Is there any way to support the other taller than wide resolutions without doubling their width? Doing so causes problems for various shaders, which don't expect/compensate for the doubled pixels.

Eyecandy: Turn your computer into an expensive lava lamp.

Reply 1 of 7, by leileilol

Posted on 2014-02-21, 02:49

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Have you tried it with vgaonly?

long live PCem

Reply 2 of 7, by kolano

Posted on 2014-02-21, 02:58

kolano Offline

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I hadn't, but now that I have, it still outputs at half resolution for 376x564 (i.e. 376x228), as well as outputting 360x400 at 720x400.

Eyecandy: Turn your computer into an expensive lava lamp.

Reply 3 of 7, by leileilol

Posted on 2014-02-21, 05:08

leileilol Offline

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That's understandable, as it's supposed to be double pixel width on real machines for those 320x400/360x480 tweaked modes also.

long live PCem

Reply 4 of 7, by kolano

Posted on 2014-02-21, 05:49

kolano Offline

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leileilol wrote:
That's understandable, as it's supposed to be double pixel width on real machines for those 320x400/360x480 tweaked modes also.

OK, but what about the 376x564 mode that outputs at half resolution (376x228) vs 752x564.

Eyecandy: Turn your computer into an expensive lava lamp.

Reply 5 of 7, by kolano

Posted on 2014-02-21, 06:00

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The options "linewise" and "multiscan" combined seem to resolve the issue, outputting a 752x564 image via ctrl-F5 for the program's 376x564 output.

I presume from leileilol's comments that it's not possible to output these resolutions without doubling the pixels horizontally.

Last edited by kolano on 2014-02-21, 08:24. Edited 1 time in total.

Eyecandy: Turn your computer into an expensive lava lamp.

Reply 6 of 7, by kolano

Posted on 2014-02-21, 06:19

kolano Offline

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Hrm, actually on closer look I'm not clear that fix works. The images seem to be output at the correct resolution, but I'm noticing the pattern generation seems to screw up, outputting the top half the pattern rather than the full resolution version. Maybe that's a bug with the program, Dial8, though.

In any case, with "linewise" and "mutliscan" on, pixels seem to be doubled in both directions, and the lower half the screen is just cut off.