HDMI versus VGA I/O board video quality for computer CRT

[goroth]

I have a computer VGA CRT monitor that supports 1048x1536 @ 86Hz and would like to connect it to the Mister.
I currently have a HDMI to 15 pin VGA adapter that I use with the OSSC to connect older consoles to my computer CRT.
The HDMI to VGA adapter also has an audio splitter.

With that said, I have a couple of questions.

1. Should I use my working HDMI to VGA adapter with the Mister?
2. Should I buy the analog I/O board with the 15 pin VGA connector?
3. What advantage does the analog I/O VGA board have over the built in HDMI on the Mister?
4. Is the video signal / quality better on the analog I/O VGA board when connected directly to a VGA monitor?
5. Is it just a scaling issue where the HDMI is being scaled and the analog VGA is not being scaled?

[FoxbatStargazer]

There's a direct_video setting that lets you output something pretty close to raw, unfiltered analog over HDMI. You feed that into an hdmi->VGA converter and you're going to get results near the same as if you plugged your VGA into the I/O board. Conversely you can also turn on the scaler on the VGA side instead so you can use higher resolutions and play around with filters if you want. So either output can do both direct analog-style and framebuffered/scaled outputs to your CRT.

The I/O board is only 16?-bit color, many cores don't use more than that but some can, especially if you use the scaler. Some say that the gain on the I/O output is low but I haven't been able to verify that. Might be lower than your average HDMI->VGA converter anyway. The output on the I/O is generally fine but you might get better results with HDMI converter.

One big advantage of the I/O board is if you want to do simultaneous or easily switched output. You can have the I/O board send out an original analog signal while the HDMI does fully upscaled. Great for streaming, recording, or just flipping back and forth between a CRT and LCD quickly.

As for audio on the I/O board, the onboard audio DAC is notoriously weak. If you aren't going to pull audio from the HDMI, you should use even a cheap standalone DAC (or a full reciever) to feed optical over min-toslink.

[EmK_IronFist]

Should I use my working HDMI to VGA adapter with the Mister?

Sure, why not? There's lots of video modes available to set in the INI config file that would work great with your monitor.

Should I buy the analog I/O board with the 15 pin VGA connector?

Probably not, you already have something that works, there's plenty of options for resolutions that will fit your display and you can even set vsync_adjust=2 to get less than a frame of latency.

If somehow less than a frame of latency is still too much for you, or if you want to let cores do resolution switching, you can use direct_video mode and also enable forced_scandoubler for navigating the main menu. You'd also have to manually enable scandoubler modes for each core that isn't 31 Khz. I personally wouldn't want to bother with this, but it might be fun to play around with.

What advantage does the analog I/O VGA board have over the built in HDMI on the Mister?

The main advantages are that it has a built-in, switchable sync-on-green circuit, component/YPbPr video works great, it comes with audio by default and it allows simultaneous output alongside HDMI. MiSTer's HDMI output also has a teeny bit of latency vs. analog output by default. Yes, the lowest latency mode is sub-frame, but that's *technically* still latency, even if it basically doesn't matter at that point. However, with direct_video mode enabled plus an HDMI-to-VGA dongle, your MiSTer's HDMI output is functionally turned into an analog out virtually identical to the IO board, though component video tends to be more iffy with most dongles and whether you have audio depends on whether your dongle has an audio output. (I noticed you said that you have an audio splitter in the mix, so barely any of this applies to your setup.)

Is the video signal / quality better on the analog I/O VGA board when connected directly to a VGA monitor?

It depends entirely on what HDMI-to-VGA dongle you've got - some are pretty terrible - and it also depends on whether or not you got the IO Board from a reputable dealer like MiSTer Add-ons rather than some rando on eBay. Generally speaking, if both are good quality, you will get good results from either. There's some technical info about how a great quality HDMI-to-VGA converter might give better overall results than the IO Board but having used both I can say the differences are not especially visible in normal conditions, and I don't love how most VGA dongles I've tried mangle component video colors in direct_video mode (but that's a me-problem.)

Is it just a scaling issue where the HDMI is being scaled and the analog VGA is not being scaled?

The reason the IO board exists isn't because the HDMI output ever had an "issue;" it's just because it provides dedicated inputs/outputs. It simplifies using the MiSTer with CRTs and other analog equipment without interfering with use of the HDMI port. Before I had the IO board, I just used direct_video mode with an HDMI-to-VGA dongle plus some custom cables for playing on my PVM. But I wanna be able to stream while playing on a CRT with minimal fuss, so having the HDMI output and analog video separated is nice.

Honestly I would recommend just using MiSTer with your HDMI-to-VGA dongle and seeing how you like it. Pick an appropriate resolution your monitor supports, then try setting vsync_adjust=2 and playing around.
If you get a nagging feeling that it's not right for you, maybe mess with an additional config file that has direct_video mode and forced_scandoubler enabled. As always, you can check out the Wiki for info on settings to play with to really see what works for you:https://github.com/MiSTer-devel/Main_Mi ... tion-Files

[C-R-T]

The direct video works better than the analog board output. The main two differences I’ve noticed are:

Analog board has fewer colors, this is clearly noticeable when looking at a colorful background picture that is selectable on the main menu.

The analog board makes the screen blink and flicker and pops loudly when a video mode is changed / a core is loaded. This doesn’t happen nearly as much with direct video.

Analog board output may also be somewhat noisier/grainier than direct video, but this may be placebo on my part.

[Yodasghost]

The reason the IO board exists isn't because the HDMI output ever had an "issue;" it's just because it provides dedicated inputs/outputs. It simplifies using the MiSTer with CRTs and other analog equipment without interfering with use of the HDMI port. Before I had the IO board, I just used direct_video mode with an HDMI-to-VGA dongle plus some custom cables for playing on my PVM. But I wanna be able to stream while playing on a CRT with minimal fuss, so having the HDMI output and analog video separated is nice.

Honestly I would recommend just using MiSTer with your HDMI-to-VGA dongle and seeing how you like it. Pick an appropriate resolution your monitor supports, then try setting vsync_adjust=2 and playing around.
If you get a nagging feeling that it's not right for you, maybe mess with an additional config file that has direct_video mode and forced_scandoubler enabled. As always, you can check out the Wiki for info on settings to play with to really see what works for you:https://github.com/MiSTer-devel/Main_Mi ... tion-Files

Hello, so I wanted to ask you a question about connecting the mister to a bvm or consumer crt via hdmi-to-VGA dongle... you mentioned you achieved this with custom cables?

I'm quite keen on avoiding the use of the io-board if I can incase we end up needing those pins for extra ram

Where I'm from 99.9% of consumer crts only have composite inputs, veeeery occasionally you'll come across BVMs/PVMs with S-Video

So the current solution in my head looks something like this

Mister-> Hdmi-to-VGA dongle -> Mavster MD2(RetroRepair) or VGA2NTSC (Mike Chi) or VGA to Composite (Antonio Villena) -> CRT TV

When I asked Antonio if this would work with his dongle he said i would need to mod the hdmi-to-VGA dongle to output power through the 9th pin (I can't solder and am not very techy so I'm not sure how I'd do this so I'm putting it as my last resort atm), RetroRepair said it wouldn't work because of power and possibly sync issues, and I'm not sure if it would work with Mike Chi's device either however I am cautiously optimistic because it is a powered device ...

I was wondering if you could give me any tips/advice on how I could get this to work?

[EmK_IronFist]

I'm not sure if it would work with Mike Chi's device either however I am cautiously optimistic because it is a powered device ...

I was wondering if you could give me any tips/advice on how I could get this to work?

Unfortunately the VGA2NTSC is an open source project and not just a product Mike sells. If you want one, you either have to order the materials and assemble it yourself or buy a ready-made one that someone else assembled. I don't know of anyone who sells pre-built boards. It seems like a great option if you can get one, though.

RGB to S-video projects are not hard to find and converting S-video to Composite is trivially easy with a passive adapter but ready-made solutions for RGB-to-S-video/Composite are rare and kind of expensive. You could get a device here that can take RGBs or RGBHV over a DE15 connector and convert it to S-video or Composite... but it's $90 USD. When you factor in shipping and the need for the HDMI-to-VGA dongle, you' would pay more than the cost of Antonio's adapter + an IO board for something that requires an external power supply. I don't see what the value is there, it seems like a lot of money and time waiting for very little additional benefit.

I'm quite keen on avoiding the use of the io-board if I can incase we end up needing those pins for extra ram

I understand that you don't want to sacrifice future functionality but there's no real plans to ditch the IO board for even more RAM in any cores current or future. That's just an idea floating around that has been suggested as a possible work-around for entirely hypothetical issues. The 128 MB modules we have right now are already more for "future-proofing" than actual full use. Also worth noting: if you want to use SNAC at all (which is essential for lightgun games on CRTs) you're going to need an IO board anyway.

So, in order of easiest to hardest solutions:
1. Get a PC CRT monitor instead if you can and use HDMI-to-VGA. (Simplest solution, probably the cheapest. Will probably not work with light guns.)

2. Just get an IO Board and Antonio's adapter.

3. Buy an expensive RGB-to-CVBS converter like the one linked above.

4. Try to learn a little bit about soldering and try and see if you can find a good DIY solution for cheap. It would be pretty easy (IMO) to make a simple VGA adapter with a USB cable attached to it to feed in 5v power, or to bodge a USB power cable onto Antonio's board with some careful effort.

[Yodasghost]

Thanks for the detailed response, really appreciate it

Honestly in terms of future proofing my only real concerns would be the Saturn and CPS3 (still a long way to go I know but this 3rd Strike in fpga what I'm hoping for) but if those can both be done on 128mb then I'm good to go really!

Thanks for the link to that device I hadn't seen it before! It looks ideal but I cant find any reviews/info about it so I'm not sure I'd pay $90+$35 shipping just to experiment...

I found a seller who has Mike's VGA2NTSC for around £30, and I already have a hdmi-to-VGA dongle so I might give that a shot.

PC-CRT is a great option and actually what I was using until it died very recently, I'll probably get a new one because it's such a functional and good looking option - but I do want a bigger CRT TV for when I'm playing fighting games with friends especially..

But yeah if all the stuff I'd like to play is doable on 128mb, then I'll ultimately go Antonio's IO board + adapter, and that'll also give me 2 player SNAC options.

Thanks again!