480i in ao486?

[thorr]

I know that generally speaking, the MiSTer scaler currently does not support interlaced resolutions. I wish it did, but it does not. However, don't some cores support interlaced resolutions on TV's? If that is the case, wouldn't it be possible for ao486 to directly support 480i? PC's back in the day supported interlaced resolutions. Can we add 640x480i as a direct resolution option for ao486 (not necessarily using the scaler) and set it up so that it works on CRT TV's? Right now, I use an HDMI to Svideo converter that provides 480i, but I would prefer the MiSTer to do this itself. Thanks!

[FoxbatStargazer]

Cores with actual analog output can push out interlaced, yes. The issue is that AO486 does not have real analog output.

Maybe (probably?) there is room on the board to do something like this, but it would take a bit of dev work.

[caad]

Even if you got the resolution right, the bigger problem would be framerates. 320x240 was common in games, but at 70Hz or other odd ones... good luck displaying that on a TV.

[SuperBabyHix]

I once had a TV out card for MS-DOS computers. It had a TSR program that would force all 200/400 line 70hz screen modes to be output as 240/480 line 60hz screen modes. My experience was that it had pretty low compatibility with games, not to mention everything became squished.

The program did not, however, convert the signal to interlaced. The ISA card had a VGA in and out as well as s-video and composite out. So you looped the VGA signal through the card and it converted to interlaced in hardware.

I would bet if you used the ao486 option to force everything to 60hz and sent a 640x480 signal to your HDMI to Svideo converter the output would be similar, though probably more compatible and not squished.

[thorr]

Thanks for the responses so far. I think I remember that there used to be fixed frequency video cards and monitors. I guess what I am proposing is that ao486 gets a fixed frequency video card implemented that is 480i. The OS would see this video card and use it's only supported resolution. I suppose this would only work in Windows though, which would not be sufficient for what I am trying to accomplish. I guess the best solution would be to improve the MiSTer scaler so it would support interlaced resolutions. That would be a dream come true and unlock the full potential of CRT TV's.

[SuperBabyHix]

I think even if you had a fixed frequency card in Mister you would run in to compatibility issues with DOS software. If the card is not VGA,EGA,CGA (or whatever the particular game or application expects) then it most likely just wont run. I think the current implementation of forcing 60hz instead of a variable refresh rate in the core settings is going to be the most compatible.

This page has some info on interfacing various OSes with fixed rate monitors. https://www.epanorama.net/documents/vga ... onfig.html

[thorr]

Thanks! Yes, agreed that DOS would be the issue in this case. It sounds like there are TSR drivers that can be loaded to make fixed frequency video cards work in DOS in some cases according to the link you provided. The MiSTer could emulate one of those video cards and then use the TSR driver in DOS. It would be a bit of a kludge, but better than nothing if we can't get 480i in the MiSTer scaler.

[thorr]

Meanwhile, I ordered one of these HDMI to Component adapters that actually supports 480i output (most don't): https://www.amazon.com/gp/product/B017LVMAWG
I hope and assume it will work better than my Tendak HDMI to SVideo adapter and produce similar output to what the MiSTer would do if it supported 480i in the scaler. Looking through the reviews, I don't know how it handles 4:3 resolutions. I know that 16:9 resolutions get displayed correctly with black bars on 4:3 CRT's. I don't know if I can send it 1440x1080p or 720x480p and have it use the full screen. I will report back on this after I receive it.

[akeley]

I'm probably missing something obvious, but what would be the benefit of 480i in this core? 320x200 looks pretty good already (as you well know since you are the timings-maker and higher res gaming is probably out of reach anyway.

I did try some DOS games in 480i on my PC crtemudriver setup and it's not too pretty...the flicker is rather heavy (though perhaps it's down to this particular solution).

[thorr]

I'm probably missing something obvious, but what would be the benefit of 480i in this core? 320x200 looks pretty good already (as you well know since you are the timings-maker and higher res gaming is probably out of reach anyway.

I did try some DOS games in 480i on my PC crtemudriver setup and it's not too pretty...the flicker is rather heavy (though perhaps it's down to this particular solution).

I want to play the 7th Guest, Sim City 2000, and other games that run at higher resolutions than 320x200 or 320x240. I hooked up my PC with HDMI to component at 480i using a custom resolution on an Nvidia card, and it looks great for arcade games that have a lot of motion. I didn't try any DOS games with little movement like Sim City 2000. How much the flicker bothers you is probably dependent on the person looking at it and how the display they are using handles it. I probably wouldn't want to play for hours and hours, but it would be great to have at least in short sessions.

[akeley]

Fair enough. Yes, I guess it does depend on a game type too, but also on hardware method. The flicker I have in crtemudriver is unbearable for static images, like Windows itself, bit better for action games (Groovymame uses it for some rotated vertical ones).
But on PS2 it does not bother me really, even in static games like jRPGs, etc. Maybe on MiSTer it would be on the lighter side.

[thorr]

It's quite possible that CRT emudriver is the issue. With my Nvidia card, I can easily tolerate the flicker in Windows, but the icons are huge which is annoying (edit: I am remembering from my custom 240p resolution - it has been awhile since I hooked up the PC so I can't remember how good 480i was vs 240p, but I was happy in both cases). It took me quite awhile of experimenting with the custom resolutions until I got a good result (similar to figuring out the timings for ao486 with 240p on the MiSTer). The CRT emudriver may not be as flexible and you get what you get. I have no idea.

[FoxbatStargazer]

Well the core already has a way to force 60hz output so I don't think that is such a stumbling block...

The hacky approach would be to let it draw its frame on the framebuffer as normal, then take half the lines and push them out through the VGA port with appropriate timing. I think this would assume a fixed 480i output resolution.

There is a modified version that switches between 720x400p and 640x400p analog output for use with VGA monitors, depending on whether you are in DOS or a game... so someone has monkeyed around with this area before.

[thorr]

I am not 100% sure what the 60Hz setting does. When setting up custom 240p scaler timings, I can use Variable or 60Hz on my CRT TV. Some people have a problem when using Variable. When using Variable, the image is slightly jittery, but otherwise the timings with the CRT work the same (positioning, sizing, etc.). I am inclined to think the 60Hz setting is more internal to the core and less to do with the actual video output.

For getting the MiSTer scaler to work with 480i, in my mind, the main challenge is getting interlaced output to be definable in the MiSTer.ini since there is no way to tell it "interlaced" on the video mode line. Once you can define an interlaced video mode, the next challenge is how to scale the output to an interlaced video mode. Perhaps the simplest approach is to output odd lines first followed by even lines from each frame from the frame buffer to complete one frame. I am pulling this out of the air, as I am no expert when it comes to the scaler.

[FoxbatStargazer]

Variable can make big issues for consumer TVs because DOS and many of its games will set 70 hz! You've got an interesting set if it can accept that. This assumes you aren't using vsync_adjust=0, which will use buffering to force the refresh to match whatever video mode you supplied.

[thorr]

Variable can make big issues for consumer TVs because DOS and many of its games will set 70 hz! You've got an interesting set if it can accept that. This assumes you aren't using vsync_adjust=0, which will use buffering to force the refresh to match whatever video mode you supplied.

This does not happen to me. I am using the HDMI output, and perhaps that is the difference. I don't think I am using vsync_adjust=0, but I have to check. Like I said, the geometry remains unchanged (it would change with a different refresh rate), and like you basically said, 70Hz wouldn't work. In my case, I can turn on variable and it works with my ~60Hz timings defined for ao486.

[SuperBabyHix]

Do you have refresh_max= set in your mister.ini perhaps?

[thorr]

Thanks, I will check this and the vsync_adjust when I get home.

Also, my 480i HDMI to component scaler was delivered, so I can report back on how well it looks/works.

[FoxbatStargazer]

The other thing is that 70hz is more the typical standard for old DOS and stuff, and that is how flynn's exoDOS packs come configured and what not. Variable means that the original software determines the refresh rate. Win95 will probably default to 60hz and its possible to set up DOS to do the same I think.

[Enthropy]

The other thing is that 70hz is more the typical standard for old DOS and stuff, and that is how flynn's exoDOS packs come configured and what not. Variable means that the original software determines the refresh rate. Win95 will probably default to 60hz and its possible to set up DOS to do the same I think.

This is not something you can set up in DOS, as far as I know. DOS was much more anarchystic then today's operation systems. Most programs handled graphics card and display on their own. Only exception is UniVBE, but some games hate it. And it can be a nuisance, when you are hunting those 2 extra kB of base RAM you need to run your old game
Give it a try, it should be somewhere on the internet. And read the documentation well. It can be a powerful tool, but it is not exactly user friendly.

[SuperBabyHix]

Enthropy is correct. It's not really until you get to VESA modes that refresh rates are typically user configurable. You didn't always have to use UniVBE though as some graphics cards manufacturers provided their own utilities for such. Not sure what would be compatible with Mister, or if it even would support different refresh rates. No matter what utility you use, the refresh rate was limited by the graphics card and its RAMDAC.

Also, 70hz really only came in to play once VGA cards hit the market. If you only had a CGA, EGA, or Tandy card, those typically used a 60hz refresh rate. Partly because some of those (CGA and Tandy), used standard definition 15Khz monitors and/or composite out to a standard def TV. Of course, running those graphics modes on a VGA card usually run at 70Hz.

There is a pretty good write up about all that here: https://nerdlypleasures.blogspot.com/20 ... rates.html

[Enthropy]

Not sure what would be compatible with Mister, or if it even would support different refresh rates. No matter what utility you use, the refresh rate was limited by the graphics card and its RAMDAC.

I did not try UniVBE on Mister, but here is some useful info for anyone, who is going to try it:
As far as I know, AO486 is simulating a Tseng ET4000 graphics card. I used to have it and it worked with UniVBE 6.5x and older. Newer versions did not detect it at all.

[thorr]

Do you have refresh_max= set in your mister.ini perhaps?

Thanks, this was the trick! I have:
refresh_min=57
refresh_max=62

With those settings, I can use the "Variable" setting and it sync's to my monitor. The Variable setting is required for Second Reality.

Without the refresh_max setting, Variable goes out of sync. I would recommend to use those settings for anyone using a CRT TV.

[thorr]

I got the 480i component converter and no matter what MiSTer timings I throw at it, it won't sync to the input signal. It sort of shows something, but it is not usable. When there is no signal, it puts up color bars that are horizontally shifted off center. I was able to use my Firestick TV 4k with it and it worked. It filled the entire screen and then some and I had to resize the picture to quite a bit smaller to not have overscan. The picture was not anamorphic/16:9 so everything was tall and skinny or squished horizontally. It was centered properly and not horizontally shifted like the color bars.

[FoxbatStargazer]

Yes for the refresh_min/max stuff, when the core's refresh goes outside of the bounds you set, Mister will act like its vsync_adjust=0, and derive the refresh from your video_mode. So even when variable is making the core push out 70 hz, its going to end up clamped back to 60 by the magic of buffering.

As for that converter, maybe it's obvious but you didn't mention anything about resolution. You can't use your existing 240p output settings, I would say minimum you probably have to give it 480p. Heck I would just start with something more standard like 1080p (video_mode=8) just to see if it works.

[thorr]

As for that converter, maybe it's obvious but you didn't mention anything about resolution. You can't use your existing 240p output settings, I would say minimum you probably have to give it 480p. Heck I would just start with something more standard like 1080p (video_mode=8) just to see if it works.

Thanks. I should have clarified, but I tried every resolution that it supports. I thought it might be defective, and when it worked with my Firestick, I was disappointed because replacing it won't help. I haven't completely given up yet, but my hopes are dashed at the moment. Hopefully we can get 480i support in the MiSTer scaler. That would be way better anyway.