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Author Topic: Cropped CRT image in some modes  (Read 302 times)

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DrChek

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Cropped CRT image in some modes
« on: September 21, 2022, 07:29:25 pm »
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

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Re: Cropped CRT image in some modes
« Reply #1 on: September 22, 2022, 04:04:32 pm »
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

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Re: Cropped CRT image in some modes
« Reply #2 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




 

DrChek

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Re: Cropped CRT image in some modes
« Reply #3 on: September 22, 2022, 05:27:41 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

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

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Re: Cropped CRT image in some modes
« Reply #4 on: September 22, 2022, 06:59:21 pm »
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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DrChek

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Re: Cropped CRT image in some modes
« Reply #5 on: September 22, 2022, 07:43:37 pm »
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.

So I can create a 2560x264 mode and force its use, but all those extra lines of resolution are drawn outside of the active area and all you get are the same 240 lines. 2560x272 starts to induce vertical rolling.

It seems that this TV is actually (currently) locked at 240p, so the only working modes are the 240p and 480i ones. The TV is from the early 2000's so I have to believe there is a way to "unlock" it, I just don't know how. I know there are a ton of adjustments in the Service Menu, but the service manual (attached) is skimpy on details. As it stands the normal VPOS and VSIZE adjustments just move and stretch those 420 lines around...

Zebidee

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Re: Cropped CRT image in some modes
« Reply #6 on: September 22, 2022, 09:08:46 pm »
What monitor presets (monitor.ini) are you using when running VMMaker?
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DrChek

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Re: Cropped CRT image in some modes
« Reply #7 on: September 22, 2022, 09:15:37 pm »
What monitor presets (monitor.ini) are you using when running VMMaker?

I've used the NTSC TV one, which just gives 240p/480i modes, which all work, and the GENERIC 15k one which give the 256p, etc.. modes, but they all have the issue where the extra lines are cut off.

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Re: Cropped CRT image in some modes
« Reply #8 on: September 23, 2022, 12:13:50 am »
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.

I may need to backtrack slightly from this comment - it might be that some TVs sold in the US market were setup as NTSC only. Outside of the US TVs seem to mostly support both PAL and NTSC.

I had a look through your service mode pdf - did not see anything specific about NTSC/PAL settings, so not sure.

From what you described, it sounds like you have blanking lines set in the service mode. You could try playing with the *BLK settings (page 18, HBLK, LBLK, RBLK, VBLK), which may have some effect on this. Also HBLS on page 22.

On page 23 there are various H & V "FREERUN" settings, like HFUP (H FREERUN FREQUENCY UP), HFFR (FORCE FREERUN), BFRE (FORCE V FREERUN), and VF50 (FORCE V FREERUN 50hz) which might free your sync up. There are also various other V & H sync settings worth looking at.

You will have to have a look and experiment.

Regarding monitor presets - sometimes I find it works better if I use multiple sets of CRT_range values, such as:


Quote
monitor "ChinaTV1", "China TV - 50/60 Hz", "4:3"
        crt_range0 15625.00-15734.26, 49.50-55.00, 1.500, 4.700, 5.800, 0.191, 0.191, 1.056, 0, 0, 192, 288, 448, 576
        crt_range1 15625.00-15734.26, 55.01-62.00, 1.500, 4.700, 4.700, 0.191, 0.191, 1.056, 0, 0, 192, 248, 448, 480


With this setup, CRTEMU will generate video modes based on "crt_range1" for modes up to 248 lines. If a mode needs more lines, then it uses "crt_range0". This will allow you to tweak the settings for "NTSC" vs "PAL" modes separately.

The bolded numbers are the maximum vertical lines each crt_range allows (progressive/interlaced).

The italic numbers I may tweak for a given TV, because they often they have problems with middle frequencies e.g. 52 to 58hz). This allows me to keep the modes close to 50hz and 60hz, while rejecting modes the TV has problems with.

You could also play around with the front/back porch settings for both horizontal and sync.

Hope this helps.


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DrChek

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Re: Cropped CRT image in some modes
« Reply #9 on: September 23, 2022, 12:45:05 am »
From what you described, it sounds like you have blanking lines set in the service mode. You could try playing with the *BLK settings (page 18, HBLK, LBLK, RBLK, VBLK), which may have some effect on this. Also HBLS on page 22.

On page 23 there are various H & V "FREERUN" settings, like HFUP (H FREERUN FREQUENCY UP), HFFR (FORCE FREERUN), BFRE (FORCE V FREERUN), and VF50 (FORCE V FREERUN 50hz) which might free your sync up. There are also various other V & H sync settings worth looking at.

You will have to have a look and experiment.

It certainly seems like there is some sort of enforced "window" that is only allowing 240 visible lines, and even if I set up a mode for more, those extra lines are never visible. I've been through all those adjustments a couple of times and I couldn't find any that allow the extra lines to become visible, but maybe I just haven't hit upon the right combination yet. I do know that any mode less than ~55.5Hz is a no go on this CRT.

Well, at least all of my horizontal games look great now! The GreenAntz definitely helped out tremendously with that. I'm probably gonna live with having to stretch my vertical games to 480 (which is what I was doing with all my games before the new setup). Not the end of the world. Maybe one day someone else who figured this out with these CRTs will come along with the secret.
« Last Edit: September 23, 2022, 12:46:58 am by DrChek »

Zebidee

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Re: Cropped CRT image in some modes
« Reply #10 on: September 23, 2022, 01:28:50 am »
It certainly seems like there is some sort of enforced "window" that is only allowing 240 visible lines, and even if I set up a mode for more, those extra lines are never visible. I've been through all those adjustments a couple of times and I couldn't find any that allow the extra lines to become visible, but maybe I just haven't hit upon the right combination yet. I do know that any mode less than ~55.5Hz is a no go on this CRT.

They probably didn't even bother to allow enabling PAL via OSD/service mode!

There may be some kind of simple hack you could do with the jungle chip, like setting a pin high/low or something. Seems like more trouble than it would be worth though.

Quote
Well, at least all of my horizontal games look great now! The GreenAntz definitely helped out tremendously with that. I'm probably gonna live with having to stretch my vertical games to 480 (which is what I was doing with all my games before the new setup). Not the end of the world. Maybe one day someone else who figured this out with these CRTs will come along with the secret.

If it is any consolation, your vertical games games would never look great on a horizontal CRT anyway. You really need to 'tate that toob for vertical games. Then, with the super resolutions, your vertical games will look great.

Where it will hurt more is for horizontal games that use more than 240 vertical lines, like Mortal Kombat (410x256@54.7hz), which you will probably have to run in 480i.
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Zebidee

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Re: Cropped CRT image in some modes
« Reply #11 on: September 23, 2022, 01:43:56 am »
Just reading operation manual, it says "Television System - American TV Standard/NTSC". So I guess that's all it does!

These particular Sonys are highly sought after, if posts on certain Facebook groups are to be believed.
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Zebidee

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Re: Cropped CRT image in some modes
« Reply #12 on: September 23, 2022, 02:00:22 am »
... and the schematic shows that they didn't even bother putting a PAL crystal on the PCB.

I've added a yellow+magenta arrow to show you where the PAL and NTSC oscillators input to the jungle chip. They only have the NTSC one there. The PAL inputs are just terminated to ground.

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DrChek

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Re: Cropped CRT image in some modes
« Reply #13 on: September 23, 2022, 09:12:27 am »
Well at least I can stop trying to chase that one down. I'm guessing most of the acclaim for these sets are with regard to classic NTSC consoles. The picture is spectacular in 240/480 modes.

At least I've learned a lot about working with CRTs in the process. 👍

abispac

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Re: Cropped CRT image in some modes
« Reply #14 on: September 23, 2022, 04:08:24 pm »
I had a trinitron with the same problem, so i ended up using 3240x240 with a bezel, look ok to be in a horizontal monitor, plus the bezel gives it a look like its a real vertical monitor.