Massive Overscan 15khz Native

RetroArch General
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#1

Hello,

I’ve just compiled retroarch git on my arch Linux box. I have tested retroarch and mme4crt builds with native 15khz resolutions but I’m getting massive horizontal Overscan.

It’s way, way to much. Almost 30 pixels per side are completely cropped.

On my original RGB SNES, the Overscan is only about 6 pixels.

It’s the same with all resolutions, even super resolutions or dynamic super resolutions. Massive Overscan on the sides, even in the retroarch GUI.

On windows, this is easy to fix, by using longer porch timings. But how to fix this on Linux? I’ve seen videos of mme4crt or other retroarch builds, delivering an output 99% of the original hardware. This is not the case for me. My real consoles don’t have that much Overscan. It’s like the porches or pixel clock isn’t right.

My hardware specs are the following.

ZOTAC gf9300 Mini ITX Board Intel Core2Duo 8600 4gb DDR2 RAM AMD Radeon HD5450 VGA 1 to UMSA scart adapter Arch Linux with retroarch-git Bang & Olufsen MX 8000 CRT TV

#2

Hi @UnixRoot,

Different flavours of Linux may give slightly different video outputs. The Linux algorithm what designed on Lubuntu and the video output is very accurate. With this being said, different video cards/drivers can also alter the output but usually only by a small amount.

Please bear in mind that no other hardware is used. Combining the VGA sync can be done via an analogue route, via a couple of diodes and resistors. This is how CRTSwitchRes has been designed. Any device that changes VSYNC and HSYNC will inevitably change porch values giving a much less accurate representation.

You can edit the custom view port settings. This should allow you to retrieve most of these lost pixels. However, this may mess with the aspect ratio.

I hope this helps.

1 Like
#3

Thanks for the quick answer.

So the problem is the UMSA Scart adapter? This is not a fancy piece of equipment. It’s just a small board which has a VGA and a sound connector. It just mixes the sync. Are you Shure it messes with my porch values?

What route should I go then? How do I connect my VGA to the Scart TV? How do I get the needed voltage? How do I get sound? I would solder something together if I had a parts list and a diagram or manual.

#4

@UnixRoot Have a look here!

https://www.arcadexpress.com/arcadevga/210-cable-arcade-vga-scart-usb-5v-12v-con-audio.html

https://www.arcadexpress.com/cableado-cables/33-cable-arcade-vga-a-euroconector-scart-con-audio.html

http://retrocables.es/tienda/index.php?id_product=55&controller=product&id_lang=1#idTab5

http://retrocables.es/tienda/index.php?id_product=442&controller=product&id_lang=1

#5

You can either adjust the horizontal overscan via the service mode in your display. You’ll have to google how to access it though coz it’s different in each model. Otherwise you can do it easily via software if you use crt emudriver and the bundled gemoetry tool that comes with it.

#6

Sorry but fiddling with the geometry is not an option. Sure, I can remove the Overscan for retroarch, but then all my real hardware has a massive underscan.

Using VMMaker and ArcadeOSD is not available on Linux. Retroarch generates each needed modeline and switches resolutions on the fly, but I can’t control the porches.

There must be something wrong with my build, because I need really strange porch timings to not overscan 20% of the image. I can’t believe, my Ultimate scart adapter is the fault, but maybe it is. It generates the sync by some logic, not just combines it.

I’m using super resolutions and shaders to correct the Overscan at the moment. But that’s not the route I want to go, because I need a lot of core or fame overrides. Also the HD5450 is on its limits on super resolutions with shaders. It starts to become unresponsive and choppy.

Using super resolutions with custom viewport settings is not an option too. It would need many many game specific overrides and mid game resolution switching would not work because of the fixed vertical resolution of the custom mode.

There is only one option left, using native resolutions.

I’ll try one of the cables mentioned before or solder something up for testing.

#7

I just got one of the cables mentioned before. Exactly the same problems as with the UMSA. Massive Overscan. The cable didn’t change anything. Exactly the same picture quality with way to much Overscan.

#8

I tried different operating systems like arch linux, lubuntu, mubuntu. I tried different VGA bios on my hd5450. I tried UMSA and the full analogue route with VGA to RGB scart cable.

Results? Nothing. Huge Overscan. Almost tripple the Overscan my real consoles produce. Real SNES, PSX, PS2 through RGB have almost no Overscan on my B&O MX 8000. Retroarch / MME4CRT produces huge Overscan in every resolution. I can’t even tune the geometry on the TV, because the Overscan is so big, it’s outside the scan area of the beam.

There has to be something happening with the porches.

#9

I am going to assume there is something wrong with your setup. Maybe some overscan options!?

This is one of our comparisons of Real vs Emulated on Genesis. https://mme4crt.alphanudesign.co.uk/forum/showthread.php?tid=51

#10

But what could be wrong?

I’m running out of ideas.

It’s definitely not the os or drivers. The problem occurs on windows and any Linux distribution I’ve tried.

It’s not the cables. The problem occurs with full analogue cables and with my UMSA.

I don’t even think it’s the TV, because my real consoles don’t have the problem. As it’s a CRT, I don’t have any overscan options to tune.

Maybe it’s the graphics card. I’m using an 512MB AMD HD5450 low profile card from Sapphire. I would need front porches of around 4 and back porches of around 9 for the image to look like my real consoles.

What could I do now? As mentioned before, I’m running out of ideas. I really need help.

#11

It’s not a real solution, but if you use a super-res, you should be able to reduce the custom width multiplier in settings > video to bring the outside edges in to fit.

#12

I have the same problem. I dont think there is a way to fix it for now, i tried almost any suggestion in the past.

My setup is: windows7 machine -> UMSA -> conventional, consumer CRT.

I always have to change the horizontal scan values via service menu when switching between emulation and my PS2. (mad overscan with emulated SNES for example)

I also had your graphicscard in the past (exactly the same), changed to a R7 240 in the hope to fix some stuff, but it was exactly the same.

Gamecube emulation is also broken it seems. I have the same underscan my PS2 has when trying to play those games (but could also be a problem that dolphin is not supported properly yet).

#13

I fixed the problem by modifying the source code. I’m getting 1:1 the same output of my real hardware now. I also found some bugs in the calculation of the horizontal shift. Maybe I’m offering a patch later.

4 Likes
#14

Patches would be greatly appreciated!

1 Like
#15

This would be indeed awesome, take your time.