MiST VGA upscaling experiments

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MiST VGA upscaling experiments

Postby Newsdee » Sat Oct 04, 2014 4:55 am

EDIT: Since the thread is getting long I decided to summarize my findings here:

Best quality/compatibility obtained with XRGB-Mini
  • You will also need something like the UMSA (VGA to SCART adapter)
  • Changing the A/D setting of the XRGB greatly reduces video noise. 133 seems to work well but try others.
  • Disabling scandoublers, if supported by a core, tends to improve image and color quality.
  • Make sure to get a European SCART connector for the upscaler, as it ships with a JP21 connector not compatible with UMSA.
  • Cons: it's a rather expensive solution...
  • Cons: only RGBHV will work if you use a UMSA adapter (other adapters might accept RGBS)

Very good results - Gonbes 8220/8200 upscaler
  • Works for most cores via RGBHV input (you need to switch source to RGBHV)
  • Upscales to 1024x768 (to show nicely on big TVs)
  • At 640x480 it solves scaling issues seen on many screens, and can be chained to a scanlines generator
  • May work for the cores that can output RGBS (not tested)
  • Cons: some cores do not work, others appear off-center and aren't playable (see Core status spreadsheet for list)
  • Cons: RGBHV 15khz not accepted (probably expects RGBS for it).

----

I've been looking for ways to connect the MiST to my XRGB Mini upscaler, both to handle 50Hz (PAL) and to capture video on my PC via HDMI.
The upscaler does not have VGA inputs; but I picked up yesterday a cheap noname VGA-to-HDMI converter in my local computer store.

It works... but the VGA box adds significant horizontal noise, so the result seems to come from a wonky VHS tape. Still better than when I recorded console videos with a camcorder pointing at the TV as a kid, though :D
Interestingly the vertical banding that other posts complain about is not present, which I think suggests the problem is with TV upscalers or their VGA handling.

My setup:
  • MiST FPGA with minimig, NES, and C64 cores
  • No-name VGA to HDMI converter (seems to output PAL at 800x600 and NTSC at 640x480)
  • XRGB Mini Framemeister (converts 50Hz to 60Hz and upscales to 1280x720p)
  • AverMedia ExtremeCap U3 to record video on a PC

Does anybody know of a video host that can accept 60fps? Also has anybody tried other kind of upscalers?

Here's a few captures that show how the result (set to 720p for best quality):

minimig core PAL:
https://www.youtube.com/watch?v=LywJLy4R-I0

minimig core NTSC (skipped to a part that shows the heavy noise from the VGA box on the OSD):
https://www.youtube.com/watch?feature=p ... FVrOM#t=56

NES core on XRGB (1280x720):
https://www.youtube.com/watch?v=uIjQRelJi5k

NES core direct feed from VGA box (640x480) (my TV stretchs this but not reflected on capture card):
https://www.youtube.com/watch?v=O7YPvfFW-gA

C64 core
For some reason the C64 core has no sound with the VGA box.
It also has heavy sync issues, so I didn't bother uploading the video.
Last edited by Newsdee on Tue Feb 17, 2015 10:59 pm, edited 7 times in total.

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Re: MiST VGA upscaling experiments

Postby mc6809e » Sat Oct 04, 2014 7:53 am

The trouble is that the signal is being sampled at a rate that isn't an integer multiple of the pixel rate. It's unlikely you'll find an inexpensive digital converter that's going to sync perfectly with the pixel rate.

A better route might be to find a converter that will take the RGB output and convert it to component video or s-video for a display that will accept those inputs.

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Re: MiST VGA upscaling experiments

Postby exxos » Sat Oct 04, 2014 9:12 am

I think a lot of people have had mixed results in doing this sort of thing. Though upscaling will degrade the video quality, at least on "cheap" converters. It would probably be better to find a TV/monitor which will upscale internally. My girlfriends HD LED TV will upscale RGB to a really clear image
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Re: MiST VGA upscaling experiments

Postby Newsdee » Sat Oct 04, 2014 11:35 am

Yes absolutely, the weakest link here is the cheap HDMI upscaler.
Conversion to HDMI is normally handled by the XRGB Mini, but it lacks VGA input so need to fit one of the other options.

Current thinking: convert the VGA RGBHV signal into RGBC (combined sync) via SCART.
In theory it works with the XRGB as reported by some DreamCast owners...

Alternative would be VGA -> YPbPr but I think that adds one more processing chip to the chain, which I'd rather avoid.

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Re: MiST VGA upscaling experiments

Postby remowilliams » Sun Oct 05, 2014 3:45 pm

I've thought about trying to feed the MiST into my XRGB Mini as SCART as well (because my monitor will not display the ZX81 or Commodore cores at all) but haven't actually got around to doing anything.

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Nov 04, 2014 2:51 pm

Finally got my hands on the VGA->SCART adapter from ArcadeForge.
http://arcadeforge.net/UMSA:::15.html

I can only do some quick testing today, but I can report the following:
  • MSX, NES, SMS, and Apple2 cores work great with it!
  • Amiga NTSC has a bit of a shaky image but otherwise OK (much better than the VGA2HDMI adapter)
  • Amiga PAL has solid image... but wrong colors for some reason (everything is pinkish)
  • C64 NTSC works sometimes
  • Atari 2600 VCS works sometimes (it didn't like the Liquid Candy demo)
  • Atari ST (NTSC) and Colecovision doesn't seem to work

The good news: when it works the upscaling is very solid (no horizontal issues from the TV upscaler) and the XRGB seems to handle 50fps -> 60fps conversion well (assuming the pink tint isn't from it).
This confirms at least the XRGB is capable of handling 480p input from SCART, which was mentioned online in some places but not clear otherwise.

The bad: there is a bit of noise introduced by using SCART, but the colors are so good it hides it. Scanlines also help hide them.
Interestingly, some modes kind of worked with the VGA2HDMI but not with the SCART route (e.g. C64). (Edit: they work, see below).

I'll test a bit more and upload some videos when I have more time.
Last edited by Newsdee on Mon Nov 10, 2014 1:01 am, edited 3 times in total.

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Nov 04, 2014 3:19 pm

Contra on the NES core (mp4 file, 50fps):
http://newsdee.com/mist/videos/MiST_NES_Contra_XRGB.mp4

Castlevania III on NES core (youtube, reduces framerate):
https://www.youtube.com/watch?v=Y3lDgaf ... GEwZ6hZJzw

Eliminator on the C64 core:
https://www.youtube.com/watch?v=9GDJRWB ... GEwZ6hZJzw

Knightmare on the MSC core:
https://www.youtube.com/watch?v=OB-2TQ_OMrk

If anybody has something they'd like me to try or record, let me know.

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Re: MiST VGA upscaling experiments

Postby remowilliams » Wed Nov 05, 2014 5:36 pm

Darn, I was hoping this route would fix my inability to display the C64 core.

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Re: MiST VGA upscaling experiments

Postby Newsdee » Thu Nov 06, 2014 7:59 am

There is still hope; I've barely spent a couple of hours on it so far. :-)

Update on Amiga:
According to the XRGB wiki the video stuttering on NTSC (60p) happens on the real machine: http://junkerhq.net/xrgb/index.php/Amiga
Also somehow the video captured by my USB capture card doesn't have the stuttering, I suppose it manages to handle the sync better.

Update on C64:
It seems to work but sometimes I need to reset the MiST one time to get it to recognize the video.
Using PAL mode (50p) gives a pink tint, exactly like the Amiga 50p mode. There must be something wrong with 50p modes, need to check online.

Others:
Coleco works great.

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Re: MiST VGA upscaling experiments

Postby MasterOfGizmo » Thu Nov 06, 2014 8:28 pm

The minimig and c64 cores don't even share a single line of code. I'd assume the screen for some reason does this by itself when trying to use a 50hz mode.

I have a Toshiba TV that has purple and green artifacts when I exceed its frequency limits.
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Re: MiST VGA upscaling experiments

Postby Newsdee » Thu Nov 06, 2014 11:03 pm

My guess is the XRGB doesn't take 576p50 input well.

Would it be possible for the cores to disable scan doubling if DIP2 is set on the board?
I can test with a recompiled core first to confirm whether that fixes it.

Edit: (could I have the source for the C64 core? I could compile it myself but I'll need HDL pointers for changing the VGA code).

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Re: MiST VGA upscaling experiments

Postby Newsdee » Wed Jan 14, 2015 10:18 pm

I've bought a Micomsoft X-Capture 1 to replace the buggy Avermedia ExtremeCap U3 (whose random crashes where driving me crazy).
Aside from being more stable, the XCapture-1 has VGA input supporting 240p and 288p.

Now I can capture video either via VGA, SCART (using the UMSA), or HDMI (using the UMSA + XRGB-Mini).
I've not had much time with it yet, but it seems I still need the HDMI route to solve the vertical banding/horizontal scaling problem seen on some cores.
It's interesting that the XRGB manages to fix the image, but then again it's built to accept odd signals from old hardware...

Here is a video on the PAL core - the vertical lines are being blurred by the compression, but you can feel the effect on the vertical scrollers at the beginning.
That said, the effect is not noticeable (IMHO) in the middle of gameplay: https://www.youtube.com/watch?v=L__62BqLS3U

It's great to be able to play an entire level without dreading the infamous crashes :D

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Feb 03, 2015 12:11 pm

Quick update to say the disable_scandoubler option of the AGA core worked like a charm. No more pink screen. :D

I noticed one quirk in the core though: it always starts in "scandoubled" 50hz then switches to whichever mode is configured. This can screw up the upscaler, but you can fix it by rebooting the upscaler to pick up the new resolution.

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Feb 03, 2015 3:13 pm

Today I've tried to use the XCapture-1 with its SCART input. Didn't work, choppy image in B&W with any settings I've tried :(

I was hoping to debug whether the "video noise" was from the SCART cable, but now I think it's from the upscaler struggling to handle non-standard formats.
Still I think it's plenty decent as you can see in the videos. Here's my longest capture to date, Explora II: https://www.youtube.com/watch?v=2wmm0lQLSHg

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Re: MiST VGA upscaling experiments

Postby TillDawn » Tue Feb 03, 2015 7:06 pm

Newsdee wrote:I was hoping to debug whether the "video noise" was from the SCART cable, but now I think it's from the upscaler struggling to handle non-standard formats.
Still I think it's plenty decent as you can see in the videos. Here's my longest capture to date, Explora II: https://www.youtube.com/watch?v=2wmm0lQLSHg

To me it looks extremely clean and very nice, and to be honest I see nothing that I would identify as "video noise". Or is that somehow masked by compression in the video? Can you point to a time in the video where it is a bit more obvious?

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Re: MiST VGA upscaling experiments

Postby Newsdee » Wed Feb 04, 2015 5:07 am

It is very faint and only noticeable on uniform background colors of grayish shades. In that video you can see some at the very beginning (in the amiga OS screen) If you play it at 720p, but compression reduces it. It's much more noticeable on the C64 core though (for example).
It's really not a problem and easily hidden by tweaking brightness and contrast settings. I only mention it as contrast with pure VGA output which is cleaner, but subject to compatibility issues ( eg. many displays hide some columns, and the same happens with the XCapture-1).

Here's one where it's a bit more obvious: http://youtu.be/-noxm7VzhfM
You'll notice the gameplay part if the screen is fine with strong vivid colors, but the dark blue background has slight flickering similar to "TV snow". You really have to be looking for it to notice though. :D

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Re: MiST VGA upscaling experiments

Postby Newsdee » Wed Feb 04, 2015 3:57 pm

Just found a fix... one can adjust the A/D level (in SPECIAL menu of the XRGB-Mini) to adapt to signal strength.

I've just tried a value of 133 for the AGA and Vic-20 cores and it made a huge difference, the noise is almost imperceptible.
Impact is core-specific though, C64 improved to a lesser extent, and it didn't help much with the Spectrum one. Still good news.

Source is this old thread on the XRGB-Mini: http://shmups.system11.org/viewtopic.ph ... 28&start=0

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Re: MiST VGA upscaling experiments

Postby TillDawn » Thu Feb 05, 2015 4:54 pm

I have now noticed what you mean (somehow looked for something completely different) and I have actually noticed it before with my Amiga 1200 and the XRGB Mini. Nice find with the A/D level. I always wondered what that setting did, since I never noticed anything obvious when I changed it. Will have to try this out.

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Re: MiST VGA upscaling experiments

Postby DrChaos » Tue Feb 17, 2015 8:58 am

The Wiki states that the "Gonbes 8220 RGB to VGA PCB Konverter" does not work. I ordered a GBS 8200 from Amazon.de (which, I think should be the same besides having only one VGA out) anyway, because I read in a German forum that someone used this combination. The scart2vga cable did not really satisfy me, because 15hz does currently not work on the c64. And I thought I give it a try for 30€ and I could use it on my A600...
But it works :) I have not tested deeply yet. I had a blank screen in the beginning, but switching the input on the "SW" button gave me a picture on the AGA and C64 cores. My first impression was that the colours were a bit bright, but I got a clear and stable image, much better than my DIY scart2vga. As said - I only did a quick test and my viewing angle was a bit strange, if anyone is interested I can report more details, but I was impressed considering the price.

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Feb 17, 2015 12:39 pm

Just to confirm, you were using the 15khz cores, right?
I wrote that in the wiki :) but at the time the feature wasn't available so my unit didn't work.

Definitely worth retesting if it's a cheaper way to resolve the upscaling issues!
Perhaps the cores should use a setting in MIST.INI to always disable the scandoubler.

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Re: MiST VGA upscaling experiments

Postby DrChaos » Tue Feb 17, 2015 12:50 pm

No. I have not tested 15Hz yet.

As far as I can see there is currently no c64 core with 15Hz, or am I wrong? In case I am wrong I need to double-check, but I am pretty sure that I used the 50Hz aga core...

BTW: Unrelated, but may be of interest for some people - in the German a1k forum someone has posted a simple mod to reduce the pixel noise of the GBS8200/8220 : http://www.a1k.org/forum/showthread.php?t=48076&highlight=GBS

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Feb 17, 2015 1:46 pm

Ah, I missed that it worked with the C64 core... that's amazing given it has very non-standard video output :)
Okay - time to try it again...

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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Feb 17, 2015 4:13 pm

WOW!! The Gonbes turns out to work quite nicely!

It doesn't work with scandoubler disabled (expects 480p on RGBHV) and not all cores work (some show an image off centre),
but it has one big advantage: it solves the scaling issues seen on many TVs / screens at a very tiny cost compared to the XRGB!

Updated the wiki and the Core status sheets to show compatibility with upscalers.

Direct capture with an X-Capture1, notice the P and g in "Page" at the bottom right:
Image

Adding a Gonbes PCB in the middle, slightly fuzzier image but larger resolution and better scaling:
Image

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Re: MiST VGA upscaling experiments

Postby Gryzor » Tue Feb 17, 2015 4:47 pm

Wow, that's impressive, even the fuzziness may be welcome by many!

Where did you buy yours?
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Re: MiST VGA upscaling experiments

Postby Newsdee » Tue Feb 17, 2015 10:41 pm

This is a very common card in the arcade world. If you use the 640x480 output you can chain it with an SLG-3000 to get (adjustable) scanlines as well.
I wrote a small FAQ about it long ago in another forum:
http://forum.arcadecontrols.com/index.p ... c=123399.0

I've bought mine here (8200 - one VGA output), but it comes without case or power supply:
http://www.arcadespareparts.com/arcade_ ... 13052.html

There at many other sellers at different prices.
Check a supplier of arcade parts in your country, it might save shipping and custom costs. People have bought it on eBay too.

My SLG is from Arcadeforge.net, where I also bought a "case" for the GBS (actually two thick plastic covers screwed together):
http://arcadeforge.net/Scaler-and-Strik ... e::14.html

As for the power supply any 5V 2A will do. I use a generic one that can be setup for different voltages, which you can probably find in a local electronic shop.
It powers both the GBS and the SLG (by connecting the SLG to a secondary power plug on the GBS).


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