English Amiga Board - View Single Post - OSSC (Open Source Scan Converter) with an Amiga

jarp · 13 November 2016, 11:07

Hi all!

I am a bit surprised that there's not much discussion about a OSSC (Open Source Scan Converter) in this forum - perhaps because it is not speicifically designed for the Amiga and it's external? Since I got my unit few days ago I decided to write few words about it. I think the OSSC resolves main problems with the Amiga's video output for many (judging from number of Amiga compatible monitor, scandoubler etc. related threads). So what is it? I'll quote XRGB wiki:

"Open Source Scan Converter is a low-latency video digitizer and scan converter board designed mainly for connecting retro video game consoles and home computers into modern displays. It converts analog RGB/component video into digital format, and doubles (or triples) scanlines of a single frame if necessary to generate a valid mode for digital TVs or monitors."

Most interesting features being (again from XRGB wiki):

* Linetriple-support for 240p/288p with 4 different sampling modes
* Very low latency (less than 2 input scanlines)
* Full-range 24-bit RGB output through DVI/HDMI

This is it:

I connected my Amiga 600 to the OSSC using a SCART lead (OSSC would take VGA also if you have VGA adapter for your amiga). BAM - it works out of the box! The OSSC has a lot of configuration options available but none of which needed to be tweaked. I know that some gaming consoles required fiddling around with settings but not Amiga it seems. However, after I used Overscan program to expand workbench screen to the max I had to adjust backporch settings a bit to get perfectly centered workbench. I also enabled linetriple mode. This is how it looks:

You'll immediatly notice that the picture is a bit small despite of linetriple mode. It is because my monitor is 27" 1440p monitor and sadly even linetriple mode is not enough. OSSC guys have promised 4x and 5x modes in the future which should address this issue also. And since it is open source, one could create custom firmware if they do not. Anyways most likely most of the people won't even have this problem because they either have full-hd displays or their displays can actually do scaling internally (mine cannot, which is a bit weird).

Some more pictures, I enabled funny background pattern to see how crisp the picture is:

Please notice that 99% of imperfections in the picture are actually due to my compact digital camera! None of there color bleeding problems are there and picture is perfectly crisp unlike in photos. There are SLIGHT imperfections in the picture (like vertical color banding) which tells that DA-AD conversion is there, but nothing which would bother me at all when actually using the Amiga:

Have to say that this is just perfect for me since VGA is not option for me at all (Indivision ECS, Jens, please do DVI version of it thanks). I can also connect other gear to the OSSC since it is not Amiga specific. Just perfect for me. I understand that many will prefer CRT but for me that's not an option because of many reasons, lack of space being one another being that 50Hz CRT triggers migraine for me (yes, my childhood was difficult beacuse of that

...

But there are problems also to be honest. The OSSC and/or my monitor has torubles syncing to any non-standard display mode. PAL works fine and while the OSSC seems to sync to NTSC mode without a problem but my monitor seems not to sync to NTSC. Any more exotic display mode wont work for me - no productivity, no Super72, nothing. Either the OSSC won't sync or my montitor won't sync or there are problems with picture quality. But PAL, it works without an problem and that's what I were looking for. Vampire 600 is there for anything else. Edit: The OSSC now synch to most of the modes when using VGA adapter.

Please notice that the OSSC won't do any frame buffering (that's why it is so good, no lag) so no scaling other than linedoubling/tripling/4x/5x... and no frame rate conversion which means that you monitor has to be able to sync to the modes also! But you just cannot get best of all worlds...

That's all I had to say about this unit...

-J

Edit: Here are pixel-perfect advanced timing settings for common Amiga modes. These settings will capture whole overscan area also. I did not include lineX3 mode settings because it's impossible to do in pixel perfect manner if correct aspect ratio is desired.

PAL:HiRes (724x284), PAL:LowRes (362x284):
240p/288p lineX3: Off
H. samplerate: 908
H. synclen: 60
H. active: 724
V. active: 284
H. backporch: 76
V. backporch: 25
Sampling phase: Adjust until you get stable and crisp picture.
Note: If V. active 284 does not work you may try 288 (PAL standard).

PAL:Super-HiRes (1440x283):
240p/288p lineX3: Off
H. samplerate: 1816
H. synclen: 72
H. active: 1440
V. active: 288
H. backporch: 198
V. backporch: 24
Sampling phase: Adjust until you get stable and crisp picture.
Note: Aspect ratio is wrong (correct one would require lineX4 support which is not there yet). But because of that mode is actually quite usable in Workbench if you have ultra widescreen monitor.

DBLPAL:High Res No Flicker (744x564), DBLPAL:Low Res No Flicker (372x564):
H. samplerate: 976
H. synclen: 96
H. active: 744
V. active: 564
H. backporch: 99
V. backporch: 10
Sampling phase: Adjust until you get stable and crisp picture.
Note: If V. active 564 does not work you may try 576 (PAL standard).

NTSC:HiRes (724x241), NTSC:LowRes (362X241):
240p/288p lineX3: Off
H. samplerate: 910
H. synclen: 60
H. active: 724
V. active: 241
H. backporch: 76
V. backporch: 16
Sampling phase: Adjust until you get stable and crisp picture.
Note: If V. active 241 does not work you may try 240 (NTSC standard).
Note: Sometimes the OSSC has troubles syncing into this mode, toggling power off and on may work.

DBLNTSC:High Res No Flicker (744X467), NTSCPAL:Low Res No Flicker (372X467):
240p/288p lineX3: Off
H. samplerate: 976
H. synclen: 20
H. active: 744
V. active: 467
H. backporch: 177
V. backporch: 74
Sampling phase: Adjust until you get stable and crisp picture.
Note: Aspect ratio is wrong (OSSC misdetects the resolution and force enables lineX2 mode). Mode may still actually be usable for Workbench use (if you have potrait monitor).
Note: Sometimes the OSSC has troubles syncing into this mode, toggling power off and on may work.

MULTISCAN:Productivity (680×495):
H. samplerate: 912
H. synclen: 96
H. active: 680
V. active: 495
H. backporch: 99
V. backporch: 12
Sampling phase: Adjust until you get stable and crisp picture.

HIGHGFX:Super-High Res (1024×384):
H. samplerate: 1304
H. synclen: 60
H. active: 1024
V. active: 384
H. backporch: 142
V. backporch: 9
Sampling phase: Adjust until you get stable and crisp picture.

HD720 (1280x360):
H. samplerate: 1576
H. synclen: 60
H. active: 1280
V. active: 360
H. backporch: 137
V. backporch: 9
Sampling phase: Adjust until you get stable and crisp picture.

13 November 2016, 11:07	#1
jarp Registered User Join Date: Apr 2016 Location: Helsinki / Finland Posts: 176	OSSC (Open Source Scan Converter) with an Amiga Hi all! I am a bit surprised that there's not much discussion about a OSSC (Open Source Scan Converter) in this forum - perhaps because it is not speicifically designed for the Amiga and it's external? Since I got my unit few days ago I decided to write few words about it. I think the OSSC resolves main problems with the Amiga's video output for many (judging from number of Amiga compatible monitor, scandoubler etc. related threads). So what is it? I'll quote XRGB wiki: "Open Source Scan Converter is a low-latency video digitizer and scan converter board designed mainly for connecting retro video game consoles and home computers into modern displays. It converts analog RGB/component video into digital format, and doubles (or triples) scanlines of a single frame if necessary to generate a valid mode for digital TVs or monitors." Most interesting features being (again from XRGB wiki): * Linetriple-support for 240p/288p with 4 different sampling modes * Very low latency (less than 2 input scanlines) * Full-range 24-bit RGB output through DVI/HDMI This is it: I connected my Amiga 600 to the OSSC using a SCART lead (OSSC would take VGA also if you have VGA adapter for your amiga). BAM - it works out of the box! The OSSC has a lot of configuration options available but none of which needed to be tweaked. I know that some gaming consoles required fiddling around with settings but not Amiga it seems. However, after I used Overscan program to expand workbench screen to the max I had to adjust backporch settings a bit to get perfectly centered workbench. I also enabled linetriple mode. This is how it looks: You'll immediatly notice that the picture is a bit small despite of linetriple mode. It is because my monitor is 27" 1440p monitor and sadly even linetriple mode is not enough. OSSC guys have promised 4x and 5x modes in the future which should address this issue also. And since it is open source, one could create custom firmware if they do not. Anyways most likely most of the people won't even have this problem because they either have full-hd displays or their displays can actually do scaling internally (mine cannot, which is a bit weird). Some more pictures, I enabled funny background pattern to see how crisp the picture is: Please notice that 99% of imperfections in the picture are actually due to my compact digital camera! None of there color bleeding problems are there and picture is perfectly crisp unlike in photos. There are SLIGHT imperfections in the picture (like vertical color banding) which tells that DA-AD conversion is there, but nothing which would bother me at all when actually using the Amiga: Have to say that this is just perfect for me since VGA is not option for me at all (Indivision ECS, Jens, please do DVI version of it thanks). I can also connect other gear to the OSSC since it is not Amiga specific. Just perfect for me. I understand that many will prefer CRT but for me that's not an option because of many reasons, lack of space being one another being that 50Hz CRT triggers migraine for me (yes, my childhood was difficult beacuse of that ... But there are problems also to be honest. The OSSC and/or my monitor has torubles syncing to any non-standard display mode. PAL works fine and while the OSSC seems to sync to NTSC mode without a problem but my monitor seems not to sync to NTSC. Any more exotic display mode wont work for me - no productivity, no Super72, nothing. Either the OSSC won't sync or my montitor won't sync or there are problems with picture quality. But PAL, it works without an problem and that's what I were looking for. Vampire 600 is there for anything else. Edit: The OSSC now synch to most of the modes when using VGA adapter. Please notice that the OSSC won't do any frame buffering (that's why it is so good, no lag) so no scaling other than linedoubling/tripling/4x/5x... and no frame rate conversion which means that you monitor has to be able to sync to the modes also! But you just cannot get best of all worlds... That's all I had to say about this unit... -J Edit: Here are pixel-perfect advanced timing settings for common Amiga modes. These settings will capture whole overscan area also. I did not include lineX3 mode settings because it's impossible to do in pixel perfect manner if correct aspect ratio is desired. PAL:HiRes (724x284), PAL:LowRes (362x284): 240p/288p lineX3: Off H. samplerate: 908 H. synclen: 60 H. active: 724 V. active: 284 H. backporch: 76 V. backporch: 25 Sampling phase: Adjust until you get stable and crisp picture. Note: If V. active 284 does not work you may try 288 (PAL standard). PAL:Super-HiRes (1440x283): 240p/288p lineX3: Off H. samplerate: 1816 H. synclen: 72 H. active: 1440 V. active: 288 H. backporch: 198 V. backporch: 24 Sampling phase: Adjust until you get stable and crisp picture. Note: Aspect ratio is wrong (correct one would require lineX4 support which is not there yet). But because of that mode is actually quite usable in Workbench if you have ultra widescreen monitor. DBLPAL:High Res No Flicker (744x564), DBLPAL:Low Res No Flicker (372x564): H. samplerate: 976 H. synclen: 96 H. active: 744 V. active: 564 H. backporch: 99 V. backporch: 10 Sampling phase: Adjust until you get stable and crisp picture. Note: If V. active 564 does not work you may try 576 (PAL standard). NTSC:HiRes (724x241), NTSC:LowRes (362X241): 240p/288p lineX3: Off H. samplerate: 910 H. synclen: 60 H. active: 724 V. active: 241 H. backporch: 76 V. backporch: 16 Sampling phase: Adjust until you get stable and crisp picture. Note: If V. active 241 does not work you may try 240 (NTSC standard). Note: Sometimes the OSSC has troubles syncing into this mode, toggling power off and on may work. DBLNTSC:High Res No Flicker (744X467), NTSCPAL:Low Res No Flicker (372X467): 240p/288p lineX3: Off H. samplerate: 976 H. synclen: 20 H. active: 744 V. active: 467 H. backporch: 177 V. backporch: 74 Sampling phase: Adjust until you get stable and crisp picture. Note: Aspect ratio is wrong (OSSC misdetects the resolution and force enables lineX2 mode). Mode may still actually be usable for Workbench use (if you have potrait monitor). Note: Sometimes the OSSC has troubles syncing into this mode, toggling power off and on may work. MULTISCAN:Productivity (680×495): H. samplerate: 912 H. synclen: 96 H. active: 680 V. active: 495 H. backporch: 99 V. backporch: 12 Sampling phase: Adjust until you get stable and crisp picture. HIGHGFX:Super-High Res (1024×384): H. samplerate: 1304 H. synclen: 60 H. active: 1024 V. active: 384 H. backporch: 142 V. backporch: 9 Sampling phase: Adjust until you get stable and crisp picture. HD720 (1280x360): H. samplerate: 1576 H. synclen: 60 H. active: 1280 V. active: 360 H. backporch: 137 V. backporch: 9 Sampling phase: Adjust until you get stable and crisp picture. Attached Thumbnails Last edited by jarp; 05 December 2016 at 23:42.