MiST VGA Compatibility

https://github.com/mist-devel/mist-board/wiki

Moderators: Mug UK, Zorro 2, Greenious, spiny, Moderator Team

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

MiST VGA Compatibility

Postby palamzy » Mon Sep 22, 2014 4:38 am

I've had my MiST for a little while now and it's great! The idea of using an FPGA is really cool and MiST has a lot of flexibility.

The one issue I've run into is the output compatibility. Maybe PAL users have less trouble but in the NTSC world, VGA 720x480 @ 60Hz is really awkward. Even though my MiST outputs on devices, it doesn't output properly. It uses really ugly scaling that tries to shrink the horizontal to 640. I was really looking forward to parading my MiST around but now I have to worry that plugging into a friend's TV (or monitor) will give us that ugly scaling.

It looks like the only option might be to buy a converter that has scaling. Those are usually min. $80+ (up to $300+) and require external power (ugh). If anyone has other ideas/suggestions that might help, please post! Since many of the old systems relied on a TV, that was part of the fun I was hoping to recreate. And the more compatible it is, the more people it will reach. Maybe there's a way it could use a more compatible VGA mode.

I'm starting a list of devices I've tried. Please message me (or post) about models you've tested and I'll be happy to add them here. I haven't had much luck :^P

I've moved the list here:
http://haps.t15.org/

Writing it out in a BBCode list is a little too messy.
Last edited by palamzy on Tue Sep 23, 2014 3:07 am, edited 2 times in total.

User avatar
Newsdee
Atari God
Atari God
Posts: 1041
Joined: Fri Sep 19, 2014 8:40 am

Re: MiST VGA Compatibility

Postby Newsdee » Mon Sep 22, 2014 2:40 pm

Video handling specific to each core and some do better than others.
Also many cores default to PAL, but once you manage to get a display you can switch to NTSC and save the config.

I'm not sure about the scaling you refer to; I didn't seem to notice any but perhaps I'm missing.
If you have an image I can try the same on my end and compare.

Anyway here's my list:

Monitors/TVs
  • PAL: S, NTSC: S - KDS Rad-5b (some scaling appears on some cores)
  • PAL: !, NTSC: Y - Samsung 193P (some VGA modes display in half the screen e.g. C64)
  • PAL: !, NTSC: Y - Samsung LA32R81 (NTSC TV, 1366*768)

Upscalers
  • PAL: !, NTSC: ! - Gonbes 8220 (arcade converter, doesn't seem to recognize the input signal, might expect 15Khz RGBS)
  • PAL: ?, NTSC: ? - XRGB Mini (very versatile converter - haven't tried - reportedly works with 31Khz if one converts the H and V sync signals of the RGBHV standard VGA to a combined sync, RGBS).
Last edited by Newsdee on Sat Sep 27, 2014 11:51 am, edited 3 times in total.

eeun
Obsessive compulsive Atari behavior
Obsessive compulsive Atari behavior
Posts: 122
Joined: Mon Sep 10, 2007 2:49 am
Location: Ontario, Canada

Re: MiST VGA Compatibility

Postby eeun » Mon Sep 22, 2014 3:29 pm

PAL: Y, NTSC: Y - Samsung SyncMaster 715v 17" LCD, US model.

- still shows a bit of scaling issues with ST cores post 167-ish, but is the only LCD I've found (and I've tried six or seven) that works with everything MiST has thrown at it.

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Mon Sep 22, 2014 8:51 pm

Newsdee wrote:Video handling specific to each core and some do better than others.
Also many cores default to PAL, but once you manage to get a display you can switch to NTSC and save the config.

I'm not sure about the scaling you refer to; I didn't seem to notice any but perhaps I'm missing.
If you have an image I can try the same on my end and compare.


I see the same problem in every core, actually:
Combined_QC.jpg


Apple 2: Notice the right side of the 'A' and the left of the second 'P'. The pixel size should be the same but the entire column of pixels is halved (or close).
Others: It's very clear in all of them but the Atari 8 one uses a large font that makes it harder to spot (you can see it in the 'O's and 'x').

This is all dependent on the horizontal position in columns. As things scroll left/right you'll see columns of pixels get squished and expand at regular intervals across the screen. Minimig has scrolling text in the GUI which shows it very clearly. I can upload a video, if necessary. My guess is that it's simply truncating every 9th column of pixels (720 - (720 / 9) = 640).
You do not have the required permissions to view the files attached to this post.

User avatar
Newsdee
Atari God
Atari God
Posts: 1041
Joined: Fri Sep 19, 2014 8:40 am

Re: MiST VGA Compatibility

Postby Newsdee » Mon Sep 22, 2014 11:06 pm

No I don't have that problem with my Samsung TV. I guess I got lucky.
Have you tried a recent firmware and cores?

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Tue Sep 23, 2014 1:42 am

Newsdee wrote:No I don't have that problem with my Samsung TV. I guess I got lucky.
Have you tried a recent firmware and cores?


Yes, I've used the most recent firmware and the cores should be up-to-date. Can you tell me the brand / model?

ctirad
Captain Atari
Captain Atari
Posts: 218
Joined: Sun Jul 15, 2012 9:44 pm

Re: MiST VGA Compatibility

Postby ctirad » Tue Sep 23, 2014 12:51 pm

palamzy wrote:I see the same problem in every core, actually:
Combined_QC.jpg


It looks to me as a typical artifacting of the internal scaling of the LCD/TV to its native resolution.

eeun
Obsessive compulsive Atari behavior
Obsessive compulsive Atari behavior
Posts: 122
Joined: Mon Sep 10, 2007 2:49 am
Location: Ontario, Canada

Re: MiST VGA Compatibility

Postby eeun » Tue Sep 23, 2014 1:49 pm

That's pretty much what I figured. The same MiST configuration that has scaling issues on an LCD looks perfect on a CRT.

ctirad
Captain Atari
Captain Atari
Posts: 218
Joined: Sun Jul 15, 2012 9:44 pm

Re: MiST VGA Compatibility

Postby ctirad » Tue Sep 23, 2014 4:06 pm

To be precise, it is the LCD what has an issue. There is not much that can be done on the MiST side except to upscale to the LCD native resolution.

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Tue Sep 23, 2014 4:36 pm

ctirad wrote:To be precise, it is the LCD what has an issue. There is not much that can be done on the MiST side except to upscale to the LCD native resolution.


Yeah, it seemed clear to me that this is the unfortunate way that the devices try to compensate. Would it not be possible to render to a frame buffer that is more compatible, such as 800x600? Even if it had borders, that would be preferable. Do you know if the cores are re-using the same VGA design or is there actually a built-in VGA frame buffer that can't be changed?

eeun wrote:That's pretty much what I figured. The same MiST configuration that has scaling issues on an LCD looks perfect on a CRT.


Yeah, I have an old CRT that it works on, as well (which is on its way out). But to me, a large part of re-implementation is being able to use it on modern devices. Otherwise, we might as well go back to RF signals ;p

ctirad
Captain Atari
Captain Atari
Posts: 218
Joined: Sun Jul 15, 2012 9:44 pm

Re: MiST VGA Compatibility

Postby ctirad » Tue Sep 23, 2014 6:43 pm

palamzy wrote:Yeah, it seemed clear to me that this is the unfortunate way that the devices try to compensate. Would it not be possible to render to a frame buffer that is more compatible, such as 800x600? Even if it had borders, that would be preferable.


Why do you think that it would be helpfull? 800x600 is still not a native resolution of the most LCDs nowdays.

Do you know if the cores are re-using the same VGA design or is there actually a built-in VGA frame buffer that can't be changed?


I have neither deep knowledge of the MiST hardware nor the used cores, but generally you can generate any resolution and timing from the FPGA if you have proper clock source and enough RAM for a framebuffer.

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Tue Sep 23, 2014 7:39 pm

ctirad wrote:Why do you think that it would be helpfull? 800x600 is still not a native resolution of the most LCDs nowdays.


It would be helpful because it would be displayed properly. 800x600 won't be the "native" mode of the displays but it's definitely supported, where 720x480 is definitely not supported. Then I could use my MiST anywhere and even when there's only HDMI (no VGA), I could use a USB-powered VGA-to-HDMI converter because all of them support 800x600 (but none of them support 720x480).

ctirad wrote:I have neither deep knowledge of the MiST hardware nor the used cores, but generally you can generate any resolution and timing from the FPGA if you have proper clock source and enough RAM for a framebuffer.


If there's nothing hardwired in the MiST (and I don't think there is), then the cores are probably implementing the same VGA module. The MiST has 32MB of RAM and can obviously handle the 720x480/576 buffer for NTSC/PAL, so I don't see why it would have any trouble with 800x600.

Of course, I know almost nothing about programming an FPGA. This might be a very difficult task. But again, I'd really like to see this resolution because it would make the MiST viable on virtually any display out there.

ctirad
Captain Atari
Captain Atari
Posts: 218
Joined: Sun Jul 15, 2012 9:44 pm

Re: MiST VGA Compatibility

Postby ctirad » Tue Sep 23, 2014 8:03 pm

palamzy wrote:It would be helpful because it would be displayed properly. 800x600 won't be the "native" mode of the displays but it's definitely supported, where 720x480 is definitely not supported.


From the point of view of the analog inputs of the modern LCD monitors there is virtually no difference between 640x480, 720x480 or 800x600 or whatever. Once the timing is in the supported range, the singal is locked, sampled and converted to the native resolution.

User avatar
MasterOfGizmo
Atari God
Atari God
Posts: 1026
Joined: Fri Feb 08, 2013 12:15 pm
Contact:

Re: AW: MiST VGA Compatibility

Postby MasterOfGizmo » Tue Sep 23, 2014 8:49 pm

palamzy wrote:If there's nothing hardwired in the MiST (and I don't think there is), then the cores are probably implementing the same VGA module. The MiST has 32MB of RAM and can obviously handle the 720x480/576 buffer for NTSC/PAL, so I don't see why it would have any trouble with 800x600.

Of course, I know almost nothing about programming an FPGA. This might be a very difficult task. But again, I'd really like to see this resolution because it would make the MiST viable on virtually any display out there.


First and most important: The video generators of the various mist cores have nothing in common. They typically don't share a single line of code. They are technically completely different graphics cards. They have one thing in common: They are not VGA compatible as their timings derive from the original machines (usually just scan doubled). And they all have different video timings. So if your screen has a problem with all of them then your screen is simply not coping with anything that has a non-vga video mode.

The 800*600 solution won't work for several reasons. Most important the timing of a 800*600 VGA mode is not a native one of any of the old machines. You get the same problem all emulators have with jumpy scrolling, tearing and what else these have. It's the one big advantage of FPGAs that they can get very close to the original timing that the embedded machine runs in perfect sync with the video. Unfortunately some screens are very picky.

The second problem is that these old machines ran software that was closely coupled to the video output. Many programs would not run at all with a real VGA mode being used. They e.g. often sync the music or even the entire gameplay to the video output.

My honest advice: Get a PC based emulator If you want/need real VGA video. The mist cannot do it and even if it could the disadvantages would be too significant.
MIST board, FPGA based Atari STE and more: https://github.com/mist-devel/mist-board/wiki

User avatar
Newsdee
Atari God
Atari God
Posts: 1041
Joined: Fri Sep 19, 2014 8:40 am

Re: AW: MiST VGA Compatibility

Postby Newsdee » Tue Sep 23, 2014 10:54 pm

MasterOfGizmo wrote:My honest advice: Get a PC based emulator If you want/need real VGA video. The mist cannot do it and even if it could the disadvantages would be too significant.


Would it work better if the cores can output RGB 15Khz, to be routed through a dedicated upscaler?
e.g. http://forum.arcadecontrols.com/index.p ... c=123399.0

I can test with my mine if somebody can send me an updated .v file.
(if it works, switching 15Khz to 31Khz might be a better use of the second dip switch, rather than NTSC vs. PAL as we've talked about previously)

Edit for palamzy: this does not solve necessarily all the problems ... but it gives the same solution used on original hardware.
The timing problems MasterOfGizmo mentions will always be there; a PC might just be better at hiding it via emulation.

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Wed Sep 24, 2014 12:51 am

MasterOfGizmo wrote:
First and most important: The video generators of the various mist cores have nothing in common. [...]

The 800*600 solution won't work for several reasons. Most important the timing of a 800*600 VGA mode is not a native one of any of the old machines. [...] The second problem is that these old machines ran software that was closely coupled to the video output. [...]

My honest advice: Get a PC based emulator If you want/need real VGA video. The mist cannot do it and even if it could the disadvantages would be too significant.


Thanks for your explanation MasterOfGizmo. I understand that these old machines were heavily tied to the video signal (and for that matter, RF!). I'm not really interested in VGA. I chose that since it has a VGA connector and the vertical refresh is the same. I know it's more complicated than that. I just want it to work on as many screens as possible and in particular, I want it to work on TVs. It'd almost be better to have S-video output, if there's no way to create VGA-compatible output (but I won't say CVBS :P). I think we will find that many monitors and TVs are picky about what they accept for VGA.

I definitely don't want another emulator. I bought a MiST because I think this is amazing technology and probably the best way for us to preserve these old machines. Old displays will eventually disappear and a clunky CRT is not what made an Atari cool, anyway. The MiST is small and low-power, which is great!

Newsdee wrote:Edit for palamzy: this does not solve necessarily all the problems ... but it gives the same solution used on original hardware.
The timing problems MasterOfGizmo mentions will always be there; a PC might just be better at hiding it via emulation.


Oh, I'm sure emulators hide lots of problems, which is why they aren't very interesting, compared ;)

I will probably try a VGA-to-HDMI (with video scaling). I wonder, though... would VGA-to-S-video be an idea? If I can avoid an expensive scaler, that would be nice.

Back to the drawing board!

User avatar
Newsdee
Atari God
Atari God
Posts: 1041
Joined: Fri Sep 19, 2014 8:40 am

Re: MiST VGA Compatibility

Postby Newsdee » Wed Sep 24, 2014 1:38 am

Newsdee wrote:I will probably try a VGA-to-HDMI (with video scaling). I wonder, though... would VGA-to-S-video be an idea? If I can avoid an expensive scaler, that would be nice.


FWIW I think the choice of VGA in the MiST is a very good compromise.
There's a reason why scalers are expensive :-)

S-Video is dying out - at least I don't see an input in modern TVs and receivers in my area; in my experience most machines now expect HDMI for digital and VGA or compobent for analog (also composite but that is horrible). Component won't work in a computer monitor, so VGA is probably the most compatible choice.

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Wed Sep 24, 2014 5:15 am

Newsdee wrote:FWIW I think the choice of VGA in the MiST is a very good compromise.
There's a reason why scalers are expensive :-)

S-Video is dying out - at least I don't see an input in modern TVs and receivers in my area; in my experience most machines now expect HDMI for digital and VGA or compobent for analog (also composite but that is horrible). Component won't work in a computer monitor, so VGA is probably the most compatible choice.


Absolutely. I don't want to use S-video but it's still available on many TVs (it's on both the TVs I can access). It's a question of what will work. I'm going to start poking around friends' TVs and see what they have (and bringing my MiST!).

The VGA port would be great but almost every device I've tried ( 7 of 8 ) reverts to 640x480, which sucks. I brought my MiST with me when I was out tonight and tried a Gateway monitor but I got the same result (640x480 ugliness).

The v-sync is still 60Hz, so it must be the horizontal sync that's a concern.

foft
Atari User
Atari User
Posts: 40
Joined: Fri Mar 14, 2014 6:19 pm

Re: MiST VGA Compatibility

Postby foft » Wed Sep 24, 2014 6:31 am

One option...

On the Replay an interesting approach is used:
http://www.fpgaarcade.com/punbb/viewtopic.php?id=133

The video converter reclocks to a standard modern tv format, adjusting pixel clock and scanline length. Though vsync has to match.

The replay has an external pll chip, not sure if that is needed for enough clock precision.

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Wed Sep 24, 2014 7:03 am

foft wrote:One option...

On the Replay an interesting approach is used:
http://www.fpgaarcade.com/punbb/viewtopic.php?id=133

The video converter reclocks to a standard modern tv format, adjusting pixel clock and scanline length. Though vsync has to match.

The replay has an external pll chip, not sure if that is needed for enough clock precision.


Thank you. I'll have a look!

User avatar
MasterOfGizmo
Atari God
Atari God
Posts: 1026
Joined: Fri Feb 08, 2013 12:15 pm
Contact:

Re: MiST VGA Compatibility

Postby MasterOfGizmo » Wed Sep 24, 2014 7:10 am

foft wrote:One option...

On the Replay an interesting approach is used:
http://www.fpgaarcade.com/punbb/viewtopic.php?id=133

The video converter reclocks to a standard modern tv format, adjusting pixel clock and scanline length. Though vsync has to match.

The replay has an external pll chip, not sure if that is needed for enough clock precision.


Juan Carlos González Amestoy did something similar for the mists Atari St core a while ago. He made a video:
https://www.youtube.com/watch?v=DF0XlG4r_B0

Unfortunately that was before a complete re-write of the entire atari video logic which was required for several things incl the STE shifter features. This option was lost in that process. Also several people had new problems with this new video.

Maybe i can convince him to re-implement it. Should actually be easier with the current shifter. Most cores already have line buffers for their scan doublers and it should only be a matter of reading the line buffers on a different clock.

But that only adjusts the pixel clock. It doesn't alter the line frequency nor the vertical scan rate. But it may indeed help with these banding effects.
MIST board, FPGA based Atari STE and more: https://github.com/mist-devel/mist-board/wiki

cutterjohn
Retro freak
Retro freak
Posts: 10
Joined: Sat Jun 19, 2010 3:25 am

Re: MiST VGA Compatibility

Postby cutterjohn » Wed Sep 24, 2014 12:25 pm

preliminarily, put down the ASUS VM247H as also apparently having scaling problems, connected directly via VGA port(also supports HDMI & DVI, panel is 1920x1080 native).

I noticed the font width problems with the MiST (STe) core, and probably also the source of the "weird" look to hires mono mode.

...and this is as far as I've gotten yet, haven't even finished setting up the STe core let alone booting even into minimig, although I did startup some of the other bit cores just to verify that everything was working OK... but didn't really pay attention to the display...

I might look into picking up a converter/scaler to connect to a Sanyo 768p "TV" which only has HDMI & compnent inputs IIRC. Any recommendations for a hopefully not super expensive one(probably only use it for the MiST and one or two other things rarely) preferably as close to any-to-any converting as possible from VGA, HDMI, S-video, component?

aside: I was surprised to find that the 247 had a VGA port as it wasn't on my list of reqs(only cared about DVI and slightly about HDMI) when purchased, VGA is dead for a while now although my Sager 7330 did come with a VGA port?!

[EDIT]
YES! At default settings(haven't tried monkeying with fw settings yet) the ASUS VM247H displays the EXACT same problems that OP's page shows, and yes apparently like others I figured initially that it was a mist problem...

The upscaling artifacts aren't horrendous at default low res(320x200) st desktop, but even by "medium" res on the VM247H alot of the text is virtually unreadable as it not only appears to have lost a column(s) of pixels it also seems to display in a VERY light grey color.

OTOH this monitor seems to have a plethora of firmware options to monkey with, which I've so far left alone as I use it with my primary desktop connected by DVI where it works fairly awesomely... (yeah it's not the best display but I originally had this fantasy that LCD monitors with speakers would have speakers at least as good as "TV" LCDs, which was, alas, not even close to the case...
[/EDIT]

palamzy
Retro freak
Retro freak
Posts: 15
Joined: Tue Aug 19, 2014 7:48 pm

Re: MiST VGA Compatibility

Postby palamzy » Tue Nov 25, 2014 8:19 pm

cutterjohn wrote:preliminarily, put down the ASUS VM247H as also apparently having scaling problems, connected directly via VGA port(also supports HDMI & DVI, panel is 1920x1080 native).
[EDIT]
YES! At default settings(haven't tried monkeying with fw settings yet) the ASUS VM247H displays the EXACT same problems that OP's page shows, and yes apparently like others I figured initially that it was a mist problem...

The upscaling artifacts aren't horrendous at default low res(320x200) st desktop, but even by "medium" res on the VM247H alot of the text is virtually unreadable as it not only appears to have lost a column(s) of pixels it also seems to display in a VERY light grey color.

OTOH this monitor seems to have a plethora of firmware options to monkey with, which I've so far left alone as I use it with my primary desktop connected by DVI where it works fairly awesomely... (yeah it's not the best display but I originally had this fantasy that LCD monitors with speakers would have speakers at least as good as "TV" LCDs, which was, alas, not even close to the case...
[/EDIT]


I added that monitor but please check to make sure it looks right on the table. I also tried another VGA->HDMI converter. It didn't work, so I ordered one with scaling, which they said would work. Hopefully, this will be the last converter. It increases the cost of the MiST by a considerable amount but hopefully, this will mean I can tow the MiST around and use it on (virtually) any TV or monitor. At least the converter is USB-powered so I should be able to draw from the MiST's USB hub and not need a separate power supply! That is a big plus, in my book.

User avatar
Paradroyd
Captain Atari
Captain Atari
Posts: 204
Joined: Tue Sep 10, 2013 10:50 pm
Contact:

Re: MiST VGA Compatibility

Postby Paradroyd » Tue Nov 25, 2014 9:19 pm

This isn't a MIST specific problem.

I have a LOT of retro hardware, and depending on which hardware is hooked up to what, with which settings, through which cables, you're almost always going to get some of this. There are SO many variables at every step that can make this better or worse (or in some cases, if you're really lucky, not noticeable) that it's almost impossible to come up with a magic setup that won't have any of this in every situation. That said, I've noticed that in general CRTs seem to deal with it a lot better or hide the effects all together, but they bring their own set of problems.

I usually run with an active VGA splitter/signal booster that simultaneously feeds the signal to a CRT and LCD. I can either leave them both on or just the one that looks best at a given moment in a given situation. It doesn't fix this (IMO unfixable) problem, but it helps.
- Paradroyd
@paradroyd on twitter

User avatar
Newsdee
Atari God
Atari God
Posts: 1041
Joined: Fri Sep 19, 2014 8:40 am

Re: MiST VGA Compatibility

Postby Newsdee » Tue Nov 25, 2014 11:12 pm

I've solved this problem with an XRGB-Mini and an UMSA (VGA2SCART) from ArcadeForge. It's not cheap, but I happened to have the device already for other retro hardware.

The XRGB is very lenient in accepting unusual signals and manages to display them in 720p, even handling 50hz to 60hz conversion if you want. It's not perfect by any means (PAL 576p50hz signals come out with a pink tint and you get some video noise from SCART) but it is very solid. It was originally designed for 240p/280p upscaling, but I've found it manages 480p well if you convert the VGA's RGBHV signal to RGBS via SCART.

It might be cheaper for some to find a monitor that works, but in my case I don't want the bulk of a CRT TV (which is the most compatible). In comparison, this kind of upscaler gives you full control over the video signal and lets you use any HDMI display. That said, it would be overkill to get it just for the MiST, but if you have other retro machines it improves their video (even with composite, which surprised me). I now have many devices wired to it (see my signature).

I've written about my experiments here: viewtopic.php?f=101&t=27019.
I've captured some videos both with a cheap VGA2HDMI converter (wobbly image) and the XRGB (all the wiki videos were taken with it).


Return to “MiST”

Who is online

Users browsing this forum: No registered users and 1 guest

cron