OSSC (Open Source Scan Converter) with an Amiga

[jbilander]

Originally Posted by Krashan

True. Having a framebuffer, Indi can produce 1280×1024 mode, which is deinterlaced and looks awesome on 17"/19" displays having exactly this native resolution.

Ok, thanks. That is good to know I'm waiting for the vampire v4 standalone (for more serious wb stuff) so I think I won't go down the Indivision mk2 route on this machine. Only use it for casual gaming, but it would have been nice to have classic wb in at least 640x512 deinterlaced. Maybe I will look into getting a cheap GBS-8220 for deinterlacing. Maybe a bit off topic but does anyone know if that board has pass-through possibilities? I'm thinking 640x512 interlaced could be handled by GBS-8220 and all other progressive modes just passed through untouched (15KHz 50Hz) to the monitor through the one and same vga cable.

[idrougge]

Don't use the GBS-8220. It looks as if you've pulled a nylon stocking over your monitor.

[jbilander]

Originally Posted by idrougge

Don't use the GBS-8220. It looks as if you've pulled a nylon stocking over your monitor.

Is the GBS-8220 really that bad? I watched this clip and I think it looks okay for some easier wb stuff in 640x512 laced.

9:09 into the clip...

[ Show youtube player ]

However I do not know if it is possible to put it in bypass mode and just pass through the signal as is. That would be great for progressive modes since the Benq monitor can handle those pretty good by itself and I don't wanna introduce unnecessary lag or 50Hz->60Hz conversion. Games (often low res) looks great on this monitor by using a simple RGB->Vga adapter (but no scanlines option of course).

[graffias79]

I will try for sure when I get home from work later but I do not believe it will accept a 31KHz signal through the RGBS port. The VGA connector on the GBS is a passthrough port I believe though.

[dalek]

If you want to improve the GBS picture, start looking here: https://github.com/ramapcsx2/gbs-control

[jbilander]

Originally Posted by graffias79

I will try for sure when I get home from work later but I do not believe it will accept a 31KHz signal through the RGBS port. The VGA connector on the GBS is a passthrough port I believe though.

Great if you can try that out. I believe the RGBS header has to be used when connecting the Amiga?. The Vga input is for RGBHV if I understand it correctly? Maybe it's me mixing up terms here (progressive and non-laced modes) but what I'm after is using gbs-8220 for PAL High res 640x512 laced when doing simple wb stuff (deinterlaced/flicker-fixed by GBS-8220) and when running games and demos switch over to pass-through effectively being the same as using simple RGB->Vga adapter to the monitor since Benq BL912 can handle 15kHz PAL input signal well for non-interlaced modes.

[jbilander]

Originally Posted by dalek

If you want to improve the GBS picture, start looking here: https://github.com/ramapcsx2/gbs-control

Thanks, will take a look... sorry for hijacking the thread.

[graffias79]

Originally Posted by jbilander

Great if you can try that out. I believe the RGBS header has to be used when connecting the Amiga?. The Vga input is for RGBHV if I understand it correctly? Maybe it's me mixing up terms here (progressive and non-laced modes) but what I'm after is using gbs-8220 for PAL High res 640x512 laced when doing simple wb stuff (deinterlaced/flicker-fixed by GBS-8220) and when running games and demos switch over to pass-through effectively being the same as using simple RGB->Vga adapter to the monitor since Benq BL912 can handle 15kHz PAL input signal well for non-interlaced modes.

Gah! I forgot last night. I will remember tonight! Yes RGBS for a 15KHz signal. I've tried feeding into the VGA port using my C= RGB to VGA adapter and got no love. I guess it doesn't expect to see 15KHz with separate H/V sync.

[jbilander]

Originally Posted by graffias79

Gah! I forgot last night. I will remember tonight! Yes RGBS for a 15KHz signal. I've tried feeding into the VGA port using my C= RGB to VGA adapter and got no love. I guess it doesn't expect to see 15KHz with separate H/V sync.

No worries. From what I've read the Vga input with RGBHV is reserved for 30.5-32.5 KHz signals which would explain why no joy with the Amigas 15 KHz signal even though you connect pin 11 (HSYNC) and pin 12 (VSYNC) from Amigas 23-pin out. I don't know if it will take 15KHz RGBS on the Vga input port, in that case I think Amigas pin 10 should be connected to vga pin 13 (HSYNC or CSYNC). Also recommended to add a 680 ohm resistor on csync line.

[graffias79]

Ok, I tried Amiga 15KHz through RGBS. That worked of course. Then I used a C= VGA adapter to try 15 KHz over the VGA port. I only got corrupted video (similar to what doublescan modes look like on a 1084 monitor). Then I tried Multiscan Productivity through the VGA port and it was also corrupted.

[jbilander]

Ok, thanks for the testing, and I guess no passthrough on rgbs header on stock firmware? I found this forum where they talk about it just being achieved, maybe I'll buy one of these boards and give it a try with custom firmware...

https://shmups.system11.org/viewtopi...28409#p1328409

[nexus]

the GBS82xx can look decent for the price factor if you intend on doing the required modding to it which the parts to do that are cheap or free if laying around
many vids and sites on it
ofc you can get a OSSC cheaper to if you built it yourself
with using monitors you can also build your own and use a logic board that is 15khz compatible they sell shit tons on ebay and you can even have them program modes you want or do that yourself if you have the know how and tools
just read the datasheet on the chipset used see if they are able to display 15khz

[Apollon]

can someone call setting for the Amiga and x5 mode ossc work perfectly?

[demolition]

Originally Posted by Apollon

can someone call setting for the Amiga and x5 mode ossc work perfectly?

I have three different settings for three different monitors. I don't think any of them are 5x though (5x256 lines is >1080p so it is too high, but 4x is perfect).

[Mr. Toast]

I finished a DIY build of the OSSC with an Amiga frame of mind for it. The 8200 just didn't cut it for me beyond basic gaming. This thing hits the sweet spot for both gaming and general WB usage.

Thank you jarp for shortening the learning curve for finding optimized settings.

[MarkJPK]

Originally Posted by jarp

Hold on, it just got better. I suspected that maybe my SCART lead does not offer perfect sync signal for the OSSC since some of the modes partially worked after I enabled aggressive sync LPF from the OSSC. SCART uses composite sync where both hsync and vsync signals are transmitted via the same conductor. Also my Amiga-SCART adapter uses resistor to approximately match TTL-level voltage of Amiga's composite sync to voltage expected by SCART.

So curious I was and I just soldered buffered VGA adapter for my Amiga where hsync vsync are transmitted separately and BOOM. The OSSC now syncs to every mode short of A2024 and Euro36. Also my monitor is able to sync every mode. Woohoo what a difference.

I don't have an oscilloscope at hand but I suspect that either Amiga's composite sync is dirty or resistor messes up voltages too much. VGA fixes everything.

Apologies for digging up an old thread but I recently purchased an OSSC and although it works brilliantly I'd like to access some of the other screen modes. A search revealed your post above and I wondered if you could give me some more details about exactly what modification you made to improve the sync?

[jarp]

Originally Posted by MarkJPK

Apologies for digging up an old thread but I recently purchased an OSSC and although it works brilliantly I'd like to access some of the other screen modes. A search revealed your post above and I wondered if you could give me some more details about exactly what modification you made to improve the sync?

So VGA is better than SCART since it uses two distinct sync signals for horizontal and vertical sync. SCART uses only one combined sync signal which may not be good enough for OSSC to decode. So I switched from Amiga RGB -> SCART cable to Amiga -> RGB VGA cable. Additionally I used *buffered* cable which means it has chip inside which kind of boosts and cleans up sync signals.

So what you need is buffered Amiga RGB to VGA cable or adapter. I made mine myself but you can buy such thing from multiple places, eBay, Amiga dealers etc.

[MarkJPK]

Originally Posted by jarp

So VGA is better than SCART since it uses two distinct sync signals for horizontal and vertical sync. SCART uses only one combined sync signal which may not be good enough for OSSC to decode. So I switched from Amiga RGB -> SCART cable to Amiga -> RGB VGA cable. Additionally I used *buffered* cable which means it has chip inside which kind of boosts and cleans up sync signals.

So what you need is buffered Amiga RGB to VGA cable or adapter. I made mine myself but you can buy such thing from multiple places, eBay, Amiga dealers etc.

Ah right I see - that's good as I already have a buffered RGB to VGA adapter so I'll have a try with that. Just wanted to make sure it wasn't something you had changed on the RGB to SCART cable.


Thanks for your help - your posts in this thread have been very helpful.

[alpine9000]

I recently got a Hydra-mini scart switcher - perfect companion to the OSSC if you have multiple Amigas



Works great!

[acidbottle]

I have an OSSC but it has yielded pretty miserable results for me (on the Amiga side), of which im certain is user error!

Using RGB scart hooked right into my Samsung 1080p TV I can have a decent crisp picture and also run high res interlace with no flicker .. awesome. Issue here is I have another system using RGB scart socket on my tv, the OSSC is connected via switcher.

Using the OSSC I can get a nice crisp picture indeed with high res only, laced mode flickers, even if I select passthrough. Cannot get x4 mode to sync whatsoever.

If I understand this gizmo and the amiga correctly … I can order a RGB to VGA adapter, plug this into the Amiga and run the cable to VGA input of the OSSC and with some tweaking use the Amiga in VGA / DblPAL etc?

Am not sure if ive understood how this device really works with the Amiga as all other systems I have no issue!

Any remarks/advice greatly appreciated.