MiSTer FPGA Forum

So let me preface this by saying I really hope CRT TV support improves in the future through either a specific I/O board or better software support.

For now, I went through all the trouble of getting a video cable to convert the analog I/O board VGA to SCART and... it sort of works? I'm in the EU, so this is going to a PAL TV, but it's a newer Sony model that should be able to handle 60Hz as well (works on a PS2 and a Wii).

The end results are very core-dependent Minimig does great, as does CPS1, among others. Resolution switches correctly and it all displays as expected.

Console cores, though? They behave very strangely. I managed to get the TV to get the horizontal refresh right on Genesis once, but ever since it misinterprets *something*, because I get two images on the display. Neo Geo, NES and SNES all do this. In some each of the two images is more corrupted than in others. Interestingly, the image is properly colored on both copies, so no RGB separation here. This happens on both PAL and NTSC. Flipping back and forth resets the picture to the different apect ratio/refresh rate in real time, but the dual image remains on both.

My common sense guess would be that this is some interpolation issue and I'm getting the two fields side by side at 30fps instead of drawn correctly, but I had not seen that happen on any other CRT output devices. Not on original hardware, obviously, but also not on a Raspberry Pi or even outputting analog video from a PC.

Any thoughts on any settings that may help at all? I tried messing with the composite synch, but leaving it off just makes for bad vsync, as you'd expect, and the SOG switch doesn't change anything on either setting. Don't wanna mess with VGA voltage unless somebody is super sure that's what's going on. Any thoughts much appreciated.

It's definitely an issue on your side (could be the cable, TV, ini settings, something I/O board specific). I have a similar setup - a newer PAL Trinitron which handles 60Hz, connected via Direct Video from MiSTer - and 95% of cores work fine, with minor caveats perhaps, but nothing as drastic as you describe.

If vga_scaler=0 then there is zero interpolation or scaling going on. It would most likely be a sync issue. (and again, vga_scaler=0 is going to output original system refresh.)

If you were playing with scandoublerfx in the HUD options before make sure to set to none. This is saved separately for every core. If you have a SoG (sync on green) physical switch you might have to disable that too.

Vga scaling is off, scandoubler is off. To be clear, this TV works with original hardware on the same machines I'm trying to emulate. There's a SNES, a Mega Drive, a Master System, a PS2 and a Wii plugged into it, so obviously I've tested all the ports. The MiSTer is fine, in that it's outputting simultaneously to HDMI and looks good, and it works well out of the VGA port with a VGA CRT on all the cores with scandoubler turned on.

The cable could be to blame, but frankly, that doesn't seem likely, considering this is a per-core problem and a bunch of cores and the menus work just fine. It does seem like a sync issue, but I have no idea why it'd happen.

That's why I was calling out in my OP that I wish MiSTer had a better handling of CRTs. There's clearly a lot more software effort gone into converting these signals into a responsive HDMI output than into ensuring the singal out of the analog board is identical to original hardware.

Digging through the forums some people point out it could be a timing/Hsync issue and some options to manually adjust it would be nice, some other people pointed at some previous efforts to build something for it, but there doesn't seem to be a consistent way to ensure that commercial 15Khz CRTs are getting the same signal out that they'd get from original devices on every core.

I think its the cable, i have zero issues on the cores you mention on my sony CRT (and also my toshiba CRT) going through VGA to RGB Scart.

GoleMMan wrote: ↑Wed May 12, 2021 2:27 pm That's why I was calling out in my OP that I wish MiSTer had a better handling of CRTs. There's clearly a lot more software effort gone into converting these signals into a responsive HDMI output than into ensuring the singal out of the analog board is identical to original hardware.

MiSTer is focused on HDMI, it's no mystery. At the same time, it works fine for majority of people using CRTs, hence why you should make absolutely sure that your side is OK first. Even if it is there is still no guarantee that it's not some peculiar problem with the TV itself.

The fact that other machines or even some cores work doesn't have to mean anything. For example, I had problems with just Atari ST and few other cores not syncing properly for a better part of the year, while everything else worked perfect, and thought my setup is fine. Month ago I tried different way of connecting (using Ultimate SCART Adapter) and all of a sudden all the problematic cores started to display properly. It was the cable's fault - in my case.

Well, I figured it out. Wasn't the hardware.

The "scandoubler FX" option under Audio/Video in the affected cores was set to something other than "none". Despite both the MiSTer .ini and the core-specific .ini having forced_scandoubler=0 that turns on the scandoubler. Turns out the word "forced" is there for a reason.

And since the displays I tried were good enough to cope with a 31Khz signal and CRTs are nothing if not obedient, the TV got two images to display per scanline and put two images on screen per scanline. Honestly, I'm mostly surprised this isn't a common noob mistake when doing TV out through the VGA port. Seems like something a bunch of people would have forgotten to turn off before me. In any case, leaving that here for the record for next time somebody stumbles onto this and needs some help.

Also, I'm actually really glad I fixed this. This thing looks super nice on an era-appropriate CRT with full RGB output.

EDIT: A good note for the cores or for the MiSTer software overall would be to add a third setting to forced_scandoubler to force scandoubler off. I get some display onscreen and I have HDMI out simultaneously, so I can fix this fairly easily, but if you accidentally leave the one core with a scandoubler setting on in a display that gives you no image at 31KHz you'd be forced to go plug in your device to an HDMI screen in order to be able to simply flip that menu option on each impacted core. I'm not sure you can tweak that setting by editing the .ini files in a computer as it currently works.

FoxbatStargazer wrote: ↑Wed May 12, 2021 12:51 pm If you were playing with scandoublerfx in the HUD options before make sure to set to none. This is saved separately for every core.

I did try to tell you. Good that it's sorted!

Yeah, I just took it to mean to check the .inis instead of going into the A/V submenu on each core. I assumed the override order was the other way around.

I think you can just delete the saved config for the core instead of having to plug it into hdmi.

GoleMMan wrote: ↑Wed May 12, 2021 11:23 am So let me preface this by saying I really hope CRT TV support improves in the future through either a specific I/O board or better software support.

For now, I went through all the trouble of getting a video cable to convert the analog I/O board VGA to SCART and... it sort of works?

I’m looking for the same setup. Do you mind sharing what cable you’ve got?

Thanks!

Robgus wrote: ↑Sat Jun 19, 2021 12:01 pm I’m looking for the same setup. Do you mind sharing what cable you’ve got?

Thanks!

If you are in the UK, then this is what I use.

https://www.ebay.co.uk/itm/114489119197

You will need a VGA to VGA cable, and a fully wired RGB Scart to Scart cable.

Robgus wrote: ↑Sat Jun 19, 2021 12:01 pm

GoleMMan wrote: ↑Wed May 12, 2021 11:23 am So let me preface this by saying I really hope CRT TV support improves in the future through either a specific I/O board or better software support.

For now, I went through all the trouble of getting a video cable to convert the analog I/O board VGA to SCART and... it sort of works?

I’m looking for the same setup. Do you mind sharing what cable you’ve got?

Thanks!

Sorry that I didn't get to this earlier. Just for reference for anyone looking for info, I have a couple of cables/adaptors. One from Antonio Villena for his line of consolized MiSTers and another one that I genuinely can't fully remember where I got. I think MiSTer AddOns? I definitely didn't try to wire my own and got the stuff from MiSTer outlets.