OSSC (Open Source Scan Converter) with an Amiga

[rabidgerry]

Originally Posted by Jope

My understanding is that these are just labels it slaps on for different combinations of refresh frequencies it sees.

The Amiga's screen modes do not correspond to any standard VESA mode.

What you select in adv.timing for whatever input mode the OSSC selects for you is what matters in any case.

Ok I get that, but then once you modify the timing like I did, suddenly under the label 640 x 384 I have actually created settings for 640 x 480.

How do we know what sample rate to use for what screen mode? It seems these figures have just materialized out of thin air online somehow.

So in order to the game Blood to display properly on my Amiga I had to bump the sample rate up to 1010 or something like that even though the output is 320 x 256. It seems all logic is out the window with the OSSC. Either that or my Amiga has a mind of it's own. Then there is that interference I get right after I stop playing the game. It's all very odd.

I realise I understand absolutely none of this btw.

I thought setting up the Hi Res Pal mode would be the way to go but as I mentioned earlier I can't get crisp image across the whole display, it just moves around as I adjust the phase.

Also I tried using Pal Lo res and and creating settings for this then trying x 4 mode to match native display of my monitor but I got no where as for some reason in overscan I still had 640 and 283 to play with. Why hadn't it scaled down to just this 362x284 in overscan settings for Lo Res?

My thinking was if I pick Lo Res and not use overscan and that way with x4 mode I should get again pixel perfect to match the native resolution of my monitor at 1280 x 1024 but I couldn't even do this! It's like none of this has any logic to it at all, just random scenarios for different screen modes.

Originally Posted by turrican9

So the BenQ BL 902TM will work at 15KHz connected directly to Amiga RGB? Does it work as well as BL 702A and BL912?

Did a search on ebay and I see cheap used BL902TM's.

Seems to be a bit of confusion about the BenQ, as reported by MrClump, the BenQ BL 902TM is a candidate for OSSC only. No one said it was capable of taking native Amiga display like these two BL 702A and BL912.

I bought a 902 for use with OSSC before I get irritated at it again and smash it up

[MrClump]

Although not Amiga specific this video gives a good grounding on how to dial in the sample rate:

[ Show youtube player ]

The Workbench chequerboard background works perfectly for this purpose.

[Jope]

Originally Posted by rabidgerry

How do we know what sample rate to use for what screen mode? It seems these figures have just materialized out of thin air online somehow.

I can only speak for myself, but trial and error and a bit of an understanding of what is going on under the bonnet.

H. active and V. active are ones we actually know from screenmode prefs. It's the size of the visible window that OSSC punches out of the signal. After that the h. samplerate is adjusted so that the samples fall on top of pixels at their strongest.

Now you can adjust the sync length and back porch so that the picture is visible.

While adjusting, the display you use should be set into some kind of 1:1 pixel mapping mode (ie. don't attempt to fill the screen) and the OSSC should be connected directly to the display without any additional converters in between.

There are some other settings at play too. For whatever multiplication mode in the output options, you must select one of the optimized modes, not generic 4:3 or 16:9. These days there are a lot of optimized modes, in the past we had fewer. When I last adjusted these, I based my settings on 320x240 optim. as far as I remember. These days I would probably experiment a bit more, but I'm just using my old settings for PAL as always.

The OSSC definitely could do with some kind of flow chart of what the signal path is and which settings are applied at which part of the process.

[rabidgerry]

Originally Posted by Jope

I can only speak for myself, but trial and error and a bit of an understanding of what is going on under the bonnet.

H. active and V. active are ones we actually know from screenmode prefs. It's the size of the visible window that OSSC punches out of the signal. After that the h. samplerate is adjusted so that the samples fall on top of pixels at their strongest.

Now you can adjust the sync length and back porch so that the picture is visible.

While adjusting, the display you use should be set into some kind of 1:1 pixel mapping mode (ie. don't attempt to fill the screen) and the OSSC should be connected directly to the display without any additional converters in between.

There are some other settings at play too. For whatever multiplication mode in the output options, you must select one of the optimized modes, not generic 4:3 or 16:9. These days there are a lot of optimized modes, in the past we had fewer. When I last adjusted these, I based my settings on 320x240 optim. as far as I remember. These days I would probably experiment a bit more, but I'm just using my old settings for PAL as always.

The OSSC definitely could do with some kind of flow chart of what the signal path is and which settings are applied at which part of the process.

This is some logic for me to actually try and digest. Thanks you

I just want to point out that my obsession for full screen is purely based upon the fact that I have a monitor with 1280 x 1024 as it's optimum native resolution so you can see where my simple math says "if I do this and do that I should get a full screen". That's just in case I am coming across as insane in this quest, which really shouldn't be as difficult.

May be when this BenQ monitor arrives it will be easier to set up on? I dunno.

[Jope]

Hope you can get it to work. I have personally given up hope on my end, I've been disappointed so many times with the scalers/zoomers inside monitors.

The OSSC Pro is an exciting product in this sense, I'm looking forward to trying it out.

[MrClump]

Originally Posted by Jope

The OSSC Pro is an exciting product in this sense, I'm looking forward to trying it out.

The Pro does look interesting, although it's a pity it still doesn't have a composite input; which still leaves computers such as the C64 out in the cold (without additional hardware).

[Jope]

Originally Posted by MrClump

The Pro does look interesting, although it's a pity it still doesn't have a composite input; which still leaves computers such as the C64 out in the cold (without additional hardware).

I have a koryuu, which I use to hook up my C64 to the OSSC. Works fine and is again pixel perfect sampling of the entire visible area (but won't fill any monitor perfectly ;-)

[rabidgerry]

Originally Posted by Jope

Hope you can get it to work. I have personally given up hope on my end, I've been disappointed so many times with the scalers/zoomers inside monitors.

The OSSC Pro is an exciting product in this sense, I'm looking forward to trying it out.

Having a look at the OSSC pro to see what that is about.

Just out of curiosity, since my main CF card uses scalos, this means I can't load the checker board pattern from WB Patterns that everyone here seems to mention regarding getting square pixels. So I have this program called monitor test which has a geometry pattern, would this be the right kind of thing I should be using to check the "squareness"?

[Jope]

You can use a premade checkerboard image and multiview or some other image viewer.

[MrClump]

Originally Posted by Jope

I have a koryuu, which I use to hook up my C64 to the OSSC. Works fine and is again pixel perfect sampling of the entire visible area (but won't fill any monitor perfectly ;-)

I've been looking at one of those, it's just that with the OSSC Pro looking to be considerably more costly that the regular OSSC it's not ideal to then be shelling out another £90 or so for a Koryuu or similar with it's resulting cable spaghetti. Just an IMO, not sure if the Retrotink 5X does composite?

[Retro-Nerd]

Yes, the Retrotink 5x Pro does composite. Over cinch and scart. But for the C64 you want of course S-Video for better image quality.

[MrClump]

Originally Posted by Retro-Nerd

Yes, the Retrotink 5x Pro does composite. Over cinch and scart. But for the C64 you want of course S-Video for better image quality.

I've just taken a look and I can see the 5X can do S-Video. It's going to be very interesting to see the two go head to head.

[Retro-Nerd]

The RT5x is great for what it is. Easy to use and very compatible since its real 1080p output. But if you want it for Amiga purposes it's maybe not 100% what you are looking for (just like the OSSC), with all the different resolutions.

[MrClump]

Originally Posted by Retro-Nerd

The RT5x is great for what it is. Easy to use and very compatible since its real 1080p output. But if you want it for Amiga purposes it's maybe not 100% what you are looking for (just like the OSSC), with all the different resolutions.

Good to know. I've been holding out for the OSSC Pro and so deliberately have avoided learning anything about the 5X until then as otherwise knowing me I would end up buying one now. :-)

[Retro-Nerd]

The OSSC Pro will be very interesting. But expect a price range from 400-450 Euro, maybe more.

[Jope]

Wish there was a 25e black metal box from amazon that would do an acceptable job. :-) It's going to be three figures no matter what Amiga to HDMI solution you choose.

[turrican9]

I have 2x BenQ BL 702As and one BL 912. They give a pretty nice picture from Amiga RGB to VGA when pixel and phaseclocks are tuned correctly.

I think I read that MrClump was using a BL 912 with his OSSC and may now use a BL 902 instead with his OSSC. I assume he will use a HDMI to DVI plug. The question is how much better is the picture when using OSSC together with a BL 912 instead of connecting it directly? Would it be worth it for me to get the OSSC?

I also have Indivision ECS and ECS V2. ECS V2 has alot of ghosting. ECS V1 not so much, but still very noticeable depending on colours. Other than the ghosting the picture is probably a bit better in some ways VS plugging my monitors directly to RGB. The picture looks a bit more detailed and more vivid in a way when scandoubled.

I also have the AGA MK2 for A1200. This gives a crystal clear picture with no ghosting of course. And it's near emulator quality.

[MrClump]

Originally Posted by turrican9

I think I read that MrClump was using a BL 912 with his OSSC and may now use a BL 902 instead with his OSSC. I assume he will use a HDMI to DVI plug. The question is how much better is the picture when using OSSC together with a BL 912 instead of connecting it directly? Would it be worth it for me to get the OSSC?

Once the settings are dialled in it looks stunning IMO, it looked good on VGA but via the OSSC my 1200 looks more like an emulator. Take a look at the photo of my Workbench to see how crispy it looks in 640x512 DBLPAL.

Yes I am using an HDMI to DVI cable.

Don’t get me wrong in thinking I got an OSSC because I was in any way unhappy with the image quality on the BL912 via VGA, because I wasn’t. The decision to switch to the OSSC had more to do with needing to connect a couple of devices to the monitor and it couldn’t remember all the settings for each.

[rabidgerry]

Think I might skip the OSSC pro in this case.

This is my final throw of the dice using it when this BenQ 902 arrives. Again I plugged the GBS 8220 + GBS Control in last night and ran in 640 x 512 Hi Res Interlaced Pal and I actually am questioning myself again as it does a really good job. I think negativity regarding the GBS boards in general are from those who used it pre custom firmware (I used to before I discovered it.) It's a totally different device now and complete cost is a fraction of the OSSC. Mind you guys are selling them pre made on ebay for shocking amounts.

[turrican9]

Originally Posted by rabidgerry

Think I might skip the OSSC pro in this case.

This is my final throw of the dice using it when this BenQ 902 arrives. Again I plugged the GBS 8220 + GBS Control in last night and ran in 640 x 512 Hi Res Interlaced Pal and I actually am questioning myself again as it does a really good job. I think negativity regarding the GBS boards in general are from those who used it pre custom firmware (I used to before I discovered it.) It's a totally different device now and complete cost is a fraction of the OSSC. Mind you guys are selling them pre made on ebay for shocking amounts.

Does the GBS board with the custom firmware support Vsync 50Hz for PAL and 60Hz Vsync for NTSC and gives smooth scrolling?

Also, have any nice pictures to look at the quality of the picture output?