Software Support > GroovyMAME

Cropped CRT image in some modes

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DrChek:
I've got my system set up and working well, except for one issue with my *x256 modes. I'll use Donkey Kong as an example. Since my CRT is mounted horizontally a super resolution mode of 2560x256 should be perfect for this game, and indeed switchres does pick that resolution:


But as you can see, the top and bottom few lines are cut off from the display:


My initial thought was that this was an overscan issue, so I went to adjust the vertical size of the image. This CRT (Sony FD Trinitron WEGA KV-24FV300) does not have adjustment pots. All the geometry adjustments are done via the service menu. Unfortunately, reducing the vertical size setting just shrinks the cropped image, it doesn't "reveal" the lost lines from the top and bottom of the image.


I'm kind of at a loss of what I can do to use these 256-line modes. Is there another TV adjustment I'm missing that would bring those lost lines back into view? Is this CRT just incapable of properly displaying these modes? I've also included the verbose output from GroovyMame with this post.

DrChek:
Fooled around with it some more today.  It almost looks like it's starting the vertical retrace before it's finished drawing the last active line and starting the first active line before it reaches the top again. Is that possible?

psakhis:
Hi,
I don't recommend this resolution for your horizontal monitor which is probably set for 240 vertical lines.

It's preferable match frequency and crop 16 lines. You can center image with sliders after that.

resolution 2560x240
unevenstretch 0
intoverscan 1




 

DrChek:

--- Quote from: psakhis on September 22, 2022, 04:18:03 pm ---Hi,
I don't recommend this resolution for your horizontal monitor which is probably set for 240 vertical lines.

It's preferable match frequency and crop 16 lines. You can center image with sliders after that.

resolution 2560x240
unevenstretch 0
intoverscan 1

--- End quote ---

Unfortunately for Donkey Kong that means not seeing the score, or not seeing the bottom of the playfield. I think I may just need to run my vertical games at 480 and uneven scale in the Y. Not ideal, but playing vertical games on a horizontal CRT is always going to be a compromise of some sort I guess.

Zebidee:
CRT TVs are not actually fixed at 240p. Maybe if set for NTSC only, but honestly have never seen that in a TV made later than early 80's. You'll likely be alright with anything up to 288 vertical lines. if the TV shows it, then you are good.

"Overscan" is a common issue with CRT TVs adapted for arcade use. Some Tvs allow adjustment via service menu.

Failing that, try deleting the 2560x256 and setting up a 2560x264 or 2560x272 super resolution. This will force GM to display the game in the higher res, while giving you extra lines into the overscan areas, so you don't lose game details. I know, is not perfect res frequency matching, but Groovymame will take up any slack and ensure your game runs at the right speed.

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