Downscaling: Problems connecting the OSSC Pro to my CRT TV via Scart

[osscboy]

Hey and hello, I hope you guys can help me with trouble shooting because I‘m at a loss at what else to do. It‘s my first foray into the world of scalers.

I bought the OSSC Pro and extra AV out extension to downscale from my pc to my Bang & Olufsen Beovision 1. Not sure if the type of CRT is important here, but the more information the merrier, I guess.

I also bought this VGA to Scart converter cable (with the light gun module):

MiSTer VGA to SCART RGB

It came with this note…

…but I figured that‘s what the extra av out extension does automatically?

Without connecting the OSSC Pro to my PC, I turned it on with the remote and set it to 480i and pushed the scaler button. When I push the scaler button, nothing on the LED screen changes to signify a mode switch. And then when the TV turns on, the picture is rolling. I recorded a video of it:

(It took me a bit to fumbling with the remote to select the correct input while filming at the same time, so please be patient)

I tried to press some random buttons on the remote because I couldn‘t find enough infos on how to continue in such a case. I mean, using the OSD is impossible with the picture moving this fast.

I read, that in some setups a sync combiner is required but I thought that‘s what extra av out extension would provide?

Is it the cable, wrong settings, missing hardware?

 

 

• This topic was modified 1 month, 3 weeks ago by osscboy.

[J5]

What resolution is the output set to? You sure its set to use the CRT out not DFP? Im just trying to help. Im pretty new to OSSC Pro

[BuckoA51]

Looking at that note that came with your cable, the cable itself does not have a sync combiner so you will need to set your OSSC Pro to composite sync mode yourself. You can do this using the OLED display on the OSSC Pro itself, expansion opt->Extra AV Out mode->RGBCS/RGBS

[osscboy]

Urks, should have typed out my reply elsewhere, it just vanished after clicking submit.

So firstly, sorry I’m replying this late but I didn’t get to fiddle some more with the OSSC till now.

Actually what did it, is exactly what you suggested, Bucko. I had to set it from “Auto” to “Extra AV Out” in the expansion settings and then switch to “RGBCS/RGBS”

Now I finally get a picture and sound, but with that different issues arose.

Firstly scaling, I set Retroarch to output at 640×480 and everything is centered perfectly on the 4:3 screen, nothing cut off at the edges. But when I run a standalone emu like Xemu and have Windows 11 set to 1440×960, a 4:3 res, the OSSC Pro scales it inside 1920x1080p oder 1200p, so I get black bars all around the picture. I already tried to set the aspect ratio manually, but for example, if set to 4:3 or Auto, it cuts off the edges or squishes it vertically. So my question, is there an option to manually set the HDMI input aspect ration to 4:3?

The second problem is with the refresh rate I presume. The games feel very sluggish, have tearing even when emu and windows it set to 60Hz. Did I get that wrong because maybe interlacing uses 60Hz for each line seperately, so it adds up to 120Hz? How do you decide between 60Hz and 59.95Hz?

Thirdly, I get constant vertical tearing all over the screen, most noticably when the camera is panning horizontally. Googling around, people seem to suggest it has something to do with getting the sync settings correct? Backporch is being mentioned a lot? So I found that setting but didn’t dare to change it yet, not knowing if I could also make it worse potentially. Do you know what to look for with the sync settings?

Oh, and one last question, in the scaling settings, there are listed several different algos like Nearest Neighbor, Bilinear (Sharp/Soft), Lanczos. Are these settings relevant for downscaling also or just for upscaling from AV to digital?

[BuckoA51]

In scaler mode you can set any aspect ratio you like, if you need to resize/reformat pillarboxed 720p or 1080p content for 4:3 I discussed that in this article – https://videogameperfection.com/2023/12/12/ossc-downscaling-delights/

Make sure you have your GPU settings set to scale on the display, not on the GPU too.

I would use progressive output modes rather than interlace. Tearing suggests some sort of frame rate miss-match, you have frame lock on yes?

Generally the scaling settings won’t make that much difference when downscaling I think, but feel free to try them.

 

• This reply was modified 1 month, 3 weeks ago by BuckoA51.

[osscboy]

Ah thanks for the link, I’ll look into it.

Make sure you have your GPU settings set to scale on the display, not on the GPU

What do you mean by that? I think I tried “integer”, “aspect ratio” and “fullscreen” in the Nvidia settings. Do you mean disable GPU scaling alltogether? Yes, that’s conveniently the only settings I didn’t try haha.

I would use progressive output modes rather than interlace.

Well, I’m using a CRT TV, 480i is all there is. If you mean the signal I’m feeding into the OSSC Pro then yes, that’s progressive.

Tearing suggests some sort of frame rate miss-match, you have frame lock on yes?

Yes, frame lock was on by default and I left it at that. The OSD also always correctly reported the same refresh rate as my PC.

While watching MarcoRetro’s “Downscaling Chronicles” review of the OSSC Pro again, I noticed how 480i WS supposedly switches the image to 4:3 and 480i to widescreen, just the opposite from what it says. So maybe that’s what was happening, I’ll have to try that out.

Still so much to do, didn’t even update yet because I forgot to order the sd card adapter. Gotta get my old Macbook Pro from the attic now and see if the sd card slot still works.

 

• This reply was modified 1 month, 3 weeks ago by osscboy.
• This reply was modified 1 month, 3 weeks ago by osscboy.

[marqs]

Keep in mind that in modern Windows it’s not always possible to fully disable GPU/desktop scaling and the resolution you select does not necessarily match the active signal which gets sent out. 1440×960 possibly is output within 1080p window as cropped or scaled which doesn’t produce good result in either case. You might want to stick with 640×480 mode if you want to keep things simple, or make a custom resolution of e.g. 1920×480 if you know what to do. To avoid tearing and stuttering, make sure you’re running in single-screen mode at 60Hz and make sure emulators use GPU Vsync as timing reference (no other throttling).

[BuckoA51]

Make sure you have your GPU settings set to scale on the display, not on the GPU

Disable GPU scaling entirely, you want the raw resolution to be passed through, as much as you can anyway.

Well, I’m using a CRT TV, 480i is all there is. If you mean the signal I’m feeding into the OSSC Pro then yes, that’s progressive.

Actually most retro games don’t use interlace at all, they used 240p, though the original Xbox didn’t that used 480i at a minimum.

[osscboy]

Hey, after a week of more tinkering and trial and error, my setup seems to be finally working quite well. So I wanted to give some feedback.

– not duplicating my screen on two monitors but projecting just to the CRT fixed the perceived heavy slowdown and unsmooth frame pacing.

– disabling GPU and monitor scaling in the NVIDIA app fixed so many issues. For some emulators like Xemu, it was also neccessary to check “override the scaling mode set by games and programms”

– on the topic of scaling, what I perceived as vertical tearing lines across the whole width of the screen had nothing to do with differing refresh rates in the end. In Retroarch “integer scaling” had to be disabled also.

– in the beginning, I had problems fitting the content on my CRT screen. Sides would be cut off whatever the resolution, whether it’d be 640×480, 720×480, 1280×960 or 1290×1080. Adjusting the advanced timings only helped some, switching the aspect ratios wasn’t met with success really also. Experimenting with “crop bounding box” settings didn’t help either. So in the end, I found out that 720×480 is neither considered 4:3 nor 16:9, but PAR 1:1!!! So switching to PAR on the OSSC and Retroarch finally fit my 1280×960 image perfectly. I havn’t tried 1440×960 yet, which would be more correct theoretically, but for whatever reason, it’s already looking good as it is. And CRU looked a bit unwieldy on my first look.

So after all this, I’m pretty happy it’s finally coming together. A few questions tho remain:

1. When the PC switches Apps, the OSSC or CRT tries to readjust resolutions which let’s the screen flicker for a bit. Is that normal or could it damage the CRT in the long run?
2. I think this is not supported through the OSSC Pro, but is it possible to automate 240p/480i switching by core, by input res, by emulator? Is that even possible technically and could be a future feature? Or can it be mapped to my remote so I don’t have to maneuver through the OSD every time? Some PSX games also switch resolutions, like for example 480i for the title or menu screens, am I out of luck here?
3. For some SNES/Megadrive and also some PSX games, mainly those with prerendered backgrounds and lots of FMVs, I couldn’t yet find a shader in Retroarch that satisfyingly replicated the look, blur of composite video. So I was thinking why not use the real thing, a composite cable. The OSSC isn’t outputting CVBS, but could it be done with an adapter like this:

 

VGA->Composite/S-Video adapter

or

https://www.syscomtec.com/de/cyp-europe-scanconverter-vga-auf-y-c-fbas-sy-pt385a.html

Edit: I also just found this https://videogameperfection.com/products/koryuu-transcoder/ on VGP.

AND if the OSSC could be upgraded to supported CVBS with such hardware, maybe a switch board could be of use if I don’t want to unplug and switch cables each time. My TV got two Scart inputs, one could be used with a composite to Scart adapter. I guess, it never ends, every solved problems makes way for more ideas. 😉

Well, well this turned out to be a bit of  a wall of text, but in the end I also wanted to leave big thanks to you two for your very helpful suggestions. I the beginning I really thought this would go nowhere.

• This reply was modified 1 month, 2 weeks ago by osscboy.
• This reply was modified 1 month, 2 weeks ago by osscboy.
• This reply was modified 1 month, 2 weeks ago by osscboy.
• This reply was modified 1 month, 2 weeks ago by osscboy.

[BuckoA51]

1) I don’t believe there’s a risk of damage here but I’m not an expert. As long as you’re not feeding a 31khz signal for any length of time it should be fine.

2) I’m not sure what you mean by automate 240p/480i switching, can you elaborate?

3) I think someone else on here (or in my e-mails) tried something similar but didn’t have much luck with it, so proceed with caution.

[osscboy]

2) Playstation 1 and I believe some Saturn games also, use different resolutions. For example they switch from 240p ingame content to 480i menus or title screens seemlessly. But it’s not really feasable or immersive to switch via remote everytime manually. So I was contemplating if the ossc could possible recognice the switch in rendering resolution and thus alter its output resolution accordingly.

3) Yeah, first try didn’t work at all. Cable gets sent back. =P

Since declaring everything is great the last time, I managed to switch from 1280×960 back to native 1x 480p rendering resolutions in Retroarch, which looked horrible before. What did it was turning on CRT switchres which I didn’t try before because I read it was only working for AMD cards. Turns out that’s not true anymore and switching to 2560×480 superresolution undid all the pixelwarping and bluriness. I also learned that “nearest neigbour” scaling in the OSSC settings, isn’t producing a sharper image as much, as pixels are actually often misaligned, especially noticable with 2d elements in 480i. So lanczos or GS scaling looks better actually, with GS more like a real ps2, which I have set up to compare.

Getting the scaling right in windows is also really fickle, like on top of the settings in the NVIDIA app, I had to go into the advanced compatibility settings of the retroarch.exe to get it to scale correctly on my screen.

[BuckoA51]

I think what you’re saying is that since the PC always outputs the same progressive resolution for emulated games, the OSSC Pro has no way of knowing if it should downscale to 240p or 480i? Yeah I don’t really see a way around that. I suppose hypothetically if you had something like Morph you could send it information over WiFi to let it know about it.. otherwise I’m not sure how you could do it.

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