OSSC (DIY video digitizer & scandoubler)

[Blair]

Seems like that idea has got lost on the way. It's certainly implementable, so I'll add that to wiki too. There has also been request for custom horizontal scale factor for 256x240 and 320x240 Line3x optimized modes (currently h-scale is fixed to 4 and 3 respectively - some people would e.g. like displaying NES/SNES at "their native" 8:7 ratio).

Fantastic! Thanks for keeping an eye out marqs.


Far as the 8:7 ratio goes, that sounds pretty cool. Native output is usually the ratio I play when using retro arch on the Wii, (although I sometimes have a habit of using my video processors to stretch things out when I feel like it, heh)


side question: I'm having a lot of trouble getting a stable image with the original Wii connected to the OSSC, 240p and 480i have a few picture dropouts, I can't get the signal to stay synced at all when its set to 480p.

anybody have some settings I can try? (I have the Wii hooked up via component, using the single system monoprice cable for Wii)

Which DVI-to-VGA converter are you using with that?

Personally I'm using both an HD fury2 and a $20 HD fury 2 clone I bought on Amazon, they seem to work identically and the output quality is fantastic. i'll probably sell the original HD fury 2 as it goes for a pretty hefty price in some places and just keep using the clone.

Spoiler

Spoiler

[Mikeyy00]

bit dark though. I'm guessing we can't change brightness on the OSSC, I'll probably have to use my TV controls?

You can, go into the "Video in proc" menu. There are offset and gain settings for all three channels. This can be used to adjust the image (including brightness). It's not really useful until profile support is added, though, since you'd have to either do it every time, or save it and have it apply to all consoles unless adjusted.

Only issue I've come across, when selecting 3x, it makes the image full screen (stretched), I can change it to 4:3 manually on the TV, but only if I'm not using the TV's game mode.. on that picture type, it only does Full/Native, and Native at 3x is stretched. 2x doesn't exhibit the same issue.

There is an aspect ratio setting for 3x, and for some reason it defaults to 16:9 (IMO that's a bad choice for the default). That setting is in the "Output opt." menu, and the one you want is "Linetriple mode". The default value is "Generic 16:9", and you want to change it to "Generic 4:3".

Remember, with all these settings that I mentioned, the settings won't remain after a power cycle unless you save them. This, however, is also very convenient, because it lets you play around with any setting without fear of making some change and not remembering how to undo it. If ever you mess up your settings while playing with them, just flip the power off and on again. Boom, settings reset to saved values.

Cheers for the info!!

(Assume there's a save option in the menu?)

[citrus3000psi]

Does anyone else lose sync with the OSSC they run the 240 lag test on the SNES? All the tests work fine except that one, I get a big NO SYNC on the OSSC LCD.

[Guspaz]

anybody have some settings I can try? (I have the Wii hooked up via component, using the single system monoprice cable for Wii)

This is probably completely unrelated to your issue, but the OSSC wouldn't sync to my Wii connected through a GARO unless I set the h-sync tolerance to 12.3us or higher (that or higher, stable sync, anything lower, unstable). Confusingly, my issue was resolved by adding a VGA cable between the GARO and the OSSC even though I'm not using the OSSC's VGA input, so it sounds like some sort of attenuation or grounding issue, but I just thought I'd mention it since it doesn't hurt to try.

(Assume there's a save option in the menu?)

I'm not in front of it now, but it's a top level menu item that is called something like "<save settings>".

[jarp]

Oh my. I was patiently waiting for 5x mode until I found out that my monitor DOES do scaling, naming of the setting was just quite weird. I watched tiny picture from my 27" 1440p monitor, until I found the setting. And my mind was instantly blown. This thing is absolutely most amazing thing there is for the retro gaming! I just wanted to say that, thanks everybody involved you just literally brought my Amiga back to life.

I would've posted some pics but seems I cannot find any free image hosting service which does not compress images so much that they lose their magic.

-J

[citrus3000psi]

I would've posted some pics but seems I cannot find any free image hosting service which does not compress images so much that they lose their magic.

-J

imgur.com

[citrus3000psi]

Does anyone else lose sync with the OSSC they run the 240 lag test on the SNES? All the tests work fine except that one, I get a big NO SYNC on the OSSC LCD.

Setting the LPF to 10mhz seems to have taken care of the problem. It also fixes some other random sync issues in some games I've tested.

[jarp]

I would've posted some pics but seems I cannot find any free image hosting service which does not compress images so much that they lose their magic.

-J

imgur.com

Great. So here goes.

Amiga Workbench in PAL mode:



Amiga Workbench in 640x480 productivity mode:



Gaming:



And scanline emulation:



Perfect.

Edit: I played around with advanced timing settings and was able to get pixel perfect results even in high res modes like 1440x283. That required heavy advanced timing settings modifications but it was possible. Truly amazing. This is photo from 1440x283 PAL mode (any imperfections are due to my camera):

[marqs]

side question: I'm having a lot of trouble getting a stable image with the original Wii connected to the OSSC, 240p and 480i have a few picture dropouts, I can't get the signal to stay synced at all when its set to 480p.

anybody have some settings I can try? (I have the Wii hooked up via component, using the single system monoprice cable for Wii)

That's strange. I have US launch model Wii and there are no sync issues on 240p/480i/480p modes when used with official component cables. My only gripe is slight jitter in 240p/480i, but that's also apparent when directly connected to CRT so it doesn't seem to be related to OSSC.

Edit: I played around with advanced timing settings and was able to get pixel perfect results even in high res modes like 1440x283. That required heavy advanced timing settings modifications but it was possible. Truly amazing. This is photo from 1440x283 PAL mode (any imperfections are due to my camera):

Nice! Could you post the settings here, so they could be copied to wiki. I also wonder if there's any Amiga HW documentation that lists all relevant parameters (especially dots per line) for various screen modes. EDIT: just saw your post on VGP forums. Keep it up!

[paulb_nl]

Nice! Could you post the settings here, so they could be copied to wiki.

Speaking of the Optimal timings wiki. It states there that NES uses 256x224 but I noticed the other day that NES games actually use the full 240 lines.

[korpse413]

Does anyone else lose sync with the OSSC they run the 240 lag test on the SNES? All the tests work fine except that one, I get a big NO SYNC on the OSSC LCD.

Setting the LPF to 10mhz seems to have taken care of the problem. It also fixes some other random sync issues in some games I've tested.

I have noticed some issues with SNES as well in the very short time I have had to toy with it since recentely obtaining my OSSC (I'll explain below). I will have to check my settings for LPF, Auto must be the default option then? This might explain all the buzz I hear of people also having issues with the SNES. Doesn't the SNES run at its own unique framerate or something?

The issues I noticed are random intervals of dropped sync in game, lasting for about 1-2 seconds. I will try and film it soon; i'm sure there is already a work around, like the above mention that I am just late to the party on and implementing.

[jarp]

Nice! Could you post the settings here, so they could be copied to wiki. I also wonder if there's any Amiga HW documentation that lists all relevant parameters (especially dots per line) for various screen modes. EDIT: just saw your post on VGP forums. Keep it up!

Yeah - I just posted "final" settings to the VGP forums (thought that people may look that forum first as it's official support forum). I think I was able to find pixel perfect H. samplerate value for every relevant progressive ECS Amiga resolution. If I understood correctly it pretty much is H. samplerate which affects horizontal accuracy, remaining settings affect just the picture size and position. And of course size is matter of opinion because of overscan and how much you want to capture it - I wanted to capture whole picture including whole overscan area but for gaming that's not perhaps the most optimal setting.

Even resolutions like 680x495 and 1440x283 looks totally crisp, no smearing, bleeding or anything. It's actually quite amazing that 1440x283 works at all with OSSC as it's quite insane resolution(!). Here's photo of 680x495 resolution showing how good the OSSC really is (again, any imperfections are due to my camera):

[paulb_nl]

I will have to check my settings for LPF, Auto must be the default option then?

The issues I noticed are random intervals of dropped sync in game, lasting for about 1-2 seconds.

Auto is for Video LPF. You need to set Sync LPF. Don't forget to save. Are you using a cable with composite video for sync?

[Mikeyy00]

Riddle me this..

My original xbox is connected via component to the OSSC.

Default 480p is fairly dark.. e.g dark areas in Halo are too dark to see a damn thing.. and I have to adjust my TV gamma.. Turning on the 2x mode for 480 works (yay!), it's a bit rougher because line doubling yadda yadda.. but the gamma is noticeably improved. To the point where I don't have to touch my tv settings..

Any idea why?

[CiREdrol]

Does anyone else lose sync with the OSSC they run the 240 lag test on the SNES? All the tests work fine except that one, I get a big NO SYNC on the OSSC LCD.

Setting the LPF to 10mhz seems to have taken care of the problem. It also fixes some other random sync issues in some games I've tested.

I have noticed some issues with SNES as well in the very short time I have had to toy with it since recentely obtaining my OSSC (I'll explain below). I will have to check my settings for LPF, Auto must be the default option then? This might explain all the buzz I hear of people also having issues with the SNES. Doesn't the SNES run at its own unique framerate or something?

The issues I noticed are random intervals of dropped sync in game, lasting for about 1-2 seconds. I will try and film it soon; i'm sure there is already a work around, like the above mention that I am just late to the party on and implementing.

I get the same thing. Just received my OSSC and recently hooked it up from my gscart. The Genesis runs sweet, however I get the same loss of sync at the display you describe above. (The OSSC LCD panel stays synced)

Apparently this is a known issue with SNES..

Hopefully this bug can be eventually squashed. SNES is a favorite system!

[jarp]

Wait, did I understand how these 240p/288p modes and line-doubling really works, perhaps somebody could enlighten me?

E.g. let's say source puts out 704x288p signal which is meant to be displayed in 4:3 CRT. First of all, pixels in this resolution are not meant to be square, rather they are twice as tall as their width is. But this is no problem since developers knew this and designed graphics accordingly. Now, when this mode is line doubled then the OSSC will sample 704 dots out of each horizontal line and will output each line twice which results in 704x576p resolution which is pretty much pixel perfect (provided timing settings are set up properly), right? Then we may have mode like 352x288p and in this mode pixels actually are meant to be square. The OSSC will again sample 704 dots out of each line effectively doubling the dots. Then it also doubles the lines which again results into 704x576p resolution which are again pixel perfect. Did I understood this correctly?

So then we have lineX3 mode and this is when I started to have troubles. If I understood correctly, it actually cannot be pixel perfect if one want's to keep correct aspect ratio? I.e. when 704x288p signal is tripled then each line is tripled but then the OSSC needs to sample each pixels 1.5 times which no longer produces pixel-perfect results but smooths the picture a bit horizontally. Right? So actually only lineX2 mode and perhaps in the future lineX4 mode can be used to produce pixel-perfect results?

Aaaaand then we have Amiga and 1440x288p mode. How in earth this was meant to be displayed back in good old days? Using 4:3 CRT pixels would be 5x as tall as their width is, no? Not sure if this mode was ever usable at all. However with the OSSC this gives interesting opportunity. In lineX3 mode one can get pretty usable "wide screen" output even though technically speaking aspect ratio is wrong compared to 4:3 CRT. But it actually looks quite nice! Edit: Haha actually I was able to dial in settings for 1440x288p mode in lineX2 mode, it just took very long time to increase sampling rate from 800 to 1816 It looks SUPERB. Who knew Amiga can do ultra wide screen modes???

Sorry about stupid questions, but I really would like to understand how these modes and line doubling/tripling works Million thanks in advance!

Edit: Ah, I was stupid enough to forget how CRT really works. Of course modes like 288p do have square pixels not 1:2 pixels. CRT beam just draws 288 lines (or so) to 4:3 monitor and that's that. Hence the "scanlines". When lines are doubled and shown in TFT panel user sees 1:2 pixels but that's only due to line doubling and scanline emulation is there for making it look more authentic. Doh, how I did forget all the basics...

- Jarp

[Unseen]

Aaaaand then we have Amiga and 1440x288p mode. How in earth this was meant to be displayed back in good old days? Using 4:3 CRT pixels would be 5x as tall as their width is, no?

CRTs do not care about horizontal pixel size at all. A CRT just sweeps the electron beam from left to right in the time between two horizontal syncs and modulate the strength of that beam by the video signal it receives. Depending on the CRT the range of horizontal sweep speeds it can generate (aka the allowed range of time between two horizontal syncs) varies, which part of the reason why some monitors accept only TV-like signals (15kHz horizontal syncs, or about 64 microseconds per line) and others accept higher-resolution modes like 480p, 1080i or the usual range of PC resolutions.

What actually defines a pixel is the (smallest) amount of time during which the video source outputs a constant color value. If the source can change the color quickly, it outputs more pixels in a line than a source that must hold the color value for a longer time before it is able to change it. If you built an analog circuit that generates a steadily rising voltage during the duration of a single line to create a color ramp, you could even output a video signal that does not have pixels at all (or inifinitely many of them) and a CRT monitor would have no problems displaying it.

Discrete horizontal pixels are just an artifact of digital video generation/processing - but there is no technical reason for them to be square, since their horizontal size is only determined by their duration. The shift to square pixels is relatively recent (IIRC VGA's 640x480 was the first square-pixel resolution on the PC) and a big reason for it is probably convenience - e.g. to rotate an image by 90° in a non-square-pixel system, it must also be scaled to ensure it still looks the same.

In summary, a 1440x288p workbench screen on the Amiga does indeed look quite squashed on a 4:3 monitor - but it still is a 4:3 image and personally I don't know anyone who used it.

[paulb_nl]

So then we have lineX3 mode and this is when I started to have troubles. If I understood correctly, it actually cannot be pixel perfect if one want's to keep correct aspect ratio? I.e. when 704x288p signal is tripled then each line is tripled but then the OSSC needs to sample each pixels 1.5 times which no longer produces pixel-perfect results but smooths the picture a bit horizontally. Right? So actually only lineX2 mode and perhaps in the future lineX4 mode can be used to produce pixel-perfect results?

Yea with 704x288p you can't keep the aspect ratio with pixel perfect linetriple but your monitor has to scale it anyway. You could output 704x864 or 1408x864 and let your monitor scale it to 4:3.

[jarp]

CRTs do not care about horizontal pixel size at all. A CRT just sweeps the electron beam from left to right in the time between two horizontal syncs and modulate the strength of that beam by the video signal it receives. Depending on the CRT the range of horizontal sweep speeds it can generate (aka the allowed range of time between two horizontal syncs) varies, which part of the reason why some monitors accept only TV-like signals (15kHz horizontal syncs, or about 64 microseconds per line) and others accept higher-resolution modes like 480p, 1080i or the usual range of PC resolutions.

What actually defines a pixel is the (smallest) amount of time during which the video source outputs a constant color value. If the source can change the color quickly, it outputs more pixels in a line than a source that must hold the color value for a longer time before it is able to change it. If you built an analog circuit that generates a steadily rising voltage during the duration of a single line to create a color ramp, you could even output a video signal that does not have pixels at all (or inifinitely many of them) and a CRT monitor would have no problems displaying it.

Discrete horizontal pixels are just an artifact of digital video generation/processing - but there is no technical reason for them to be square, since their horizontal size is only determined by their duration. The shift to square pixels is relatively recent (IIRC VGA's 640x480 was the first square-pixel resolution on the PC) and a big reason for it is probably convenience - e.g. to rotate an image by 90° in a non-square-pixel system, it must also be scaled to ensure it still looks the same.

In summary, a 1440x288p workbench screen on the Amiga does indeed look quite squashed on a 4:3 monitor - but it still is a 4:3 image and personally I don't know anyone who used it.

Thanks, of course - I forgot the basics, doh! Interesting thing I found out about 1440x288p, since Workbench programs do not probably take aspect ratio into account ant all, if 1440x288p resolution is displayed in PC monitor using 1440x576p mode it quite usable. I mean technically speaking resulting picture speaking has wrong aspect ratio compared to displaying the image using 4:3 CRT, but programs do not know it and they happily draw what they draw and end result is equivalent of having dual monitor Amiga setup:

[NJRoadfan]

Maybe Commodore was thinking ahead when they implemented those modes. Whats with the Workbench 1.x color theme?

[jarp]

Maybe Commodore was thinking ahead when they implemented those modes. Whats with the Workbench 1.x color theme?

Technically speaking I just adjusted palette of the WB3.1 to match WB1.x colors and then adjusted all the color settings until I got WB1.x feeling into my WB3.1. Only problem was that WB3.1 does not allow changing which palette "slot" text will use so WB1.x colors are on wrong "slots" thus I also had to edit every single icon and reverse their palette. ClassicWB would've done that for me but I wanted to keep WB3.1 as close as stock as possible.

Sentimentally speaking my mind was blown first time in my life as a kid when I saw Amiga 500 running WB1.x and of course some games. Nothing ever since have impressed me so much and probably nothing ever will (not even VR, which also an experience which caught me totally unguarded).

[Guspaz]

Forgive my ignorance, but what in particular was so revalatory about it? It looks significantly less impressive than similar machines from the same era, such as the earlier Mac II.

Then again, Amiga was never a thing here, so I never saw one in person back in the day.

[orange808]

Forgive my ignorance, but what in particular was so revalatory about it? It looks significantly less impressive than similar machines from the same era, such as the earlier Mac II.

Then again, Amiga was never a thing here, so I never saw one in person back in the day.

It's a Commodore. Mac had no sprites. Mac had no game dev support. (They still don't.)

Commodore never bothered pretending that monochrome displays were appealing. Mac had to battle a reputation for monochrome displays and word processing.

Mac didn't support multitasking; while limited, the Amiga did.

Amiga combined gaming, productivity, and a good GUI into one package. (Amiga had plenty of shortcomings that doomed the brand, but I focused on sharing what made them great.)

[Harrumph]

Forgive my ignorance, but what in particular was so revalatory about it? It looks significantly less impressive than similar machines from the same era, such as the earlier Mac II.

Then again, Amiga was never a thing here, so I never saw one in person back in the day.

It was much much much cheaper than a Mac. And people were coming off of the C64, with its rudimentary interface and game graphics.

[neorichieb1971]

The Amiga was amazing.

The "State of the art" demo fit on a 512k disc. amazing what a 7mhz processor can do with a few graphics tricks.

https://www.youtube.com/watch?v=89wq5EoXy-0

The anti lemming demo - https://www.youtube.com/watch?v=N5N2R5JME3o

Anyway, back on topic.

[jarp]

Forgive my ignorance, but what in particular was so revalatory about it? It looks significantly less impressive than similar machines from the same era, such as the earlier Mac II.

Then again, Amiga was never a thing here, so I never saw one in person back in the day.

Since you asked me I will give an answer even though I would appreciate this thread will not degenerate to fighting over which retro platform was the best Answer is extremely simple; somebody actually had an Amiga (and Atari ST of course) - nobody I knew had an Apple. Also as a kid games were the biggest thing - no kid cares about productivity stuff. I am too young to actually understand how market was back then but I think Apple was pretty much for professional use only, while Amiga was primarily a gaming platform (which had some use in some professional work also just like Atari ST saw some professional use)? At least in the Europe, I think Amiga was not that popular in the Northern America and thus your curiosity is natural? So it's quite logical I was a) exposed to an Amiga and b) was impressed by it's gaming capabilities.

If I would be 30 years older things probably would be a bit different but since you asked why *I* was impressed, that does not matter. But to be honest, I *still* am impressed what Commodore actually was able to achieve back then but for different reasons. Amiga OS is actually pretty cool considered the time it was released. Of course back then I did not understand it but now I do. It had some much unused potential as the platform was so much skewed to the gaming. It is super interesting question actually; should Commodore had not failed so hard as it did, could Amiga have successfully competed with the Apple? PC no, but perhaps Apple?

But this is too much off-topic already I think?

Edit: Also, I has to check, Amiga 500 was USD 699 at 1987, Apple Macintosh II was USD 5500 at 1987 and more than USD 10k with all the bells and whistles. That's a lot of money. Explains why Apple was so rare back then.

[BuckoA51]

Forgive my ignorance, but what in particular was so revalatory about it? It looks significantly less impressive than similar machines from the same era, such as the earlier Mac II.

Earlier Mac 2? He's emulating the look and feel of Workbench 1.3, Workbench 1 came out in 1985 with the Amiga 1000. A year after the first Mac.

The machines multitasking capabilities really blew the Mac out of the water too, in fact I was still using my heavily expanded Amiga system right up until 2000. It really wasn't until Windows XP that the PC felt like it'd closed the gap significantly.

could Amiga have successfully competed with the Apple? PC no, but perhaps Apple?

Apple thought initially in 1985 the Amiga would blow them out of the water, but Commodore were more interested in quick fixes and selling the machine as some sort of C64 on rocket fuel. The machines whole life was one big missed opportunity really.

[jarp]

I also wonder if there's any Amiga HW documentation that lists all relevant parameters (especially dots per line) for various screen modes. EDIT: just saw your post on VGP forums. Keep it up!

Btw. I found out utitlity which dumps out (and allows modifying) highly technical detatils about Amiga's screenmodes. If there's any need, I can go through all modes and dump settings for you. Just let me know if there is.

It dumps out values in nS though, e.g. for HighGFX mode (which looks very cool BTW) it output values like this:

HScanFreq: 21.89 kHz
VScanFreq: 54.19 Hz
ColColock: 281.94 ns
Scanline: 45.67 us
HBlank: 8.18 us
HSync: 2.54 us
VBlank: 913.48 us
VSync: 274.04 us
CSDelay: 264.04 us

-J

[marqs]

Riddle me this..

My original xbox is connected via component to the OSSC.

Default 480p is fairly dark.. e.g dark areas in Halo are too dark to see a damn thing.. and I have to adjust my TV gamma.. Turning on the 2x mode for 480 works (yay!), it's a bit rougher because line doubling yadda yadda.. but the gamma is noticeably improved. To the point where I don't have to touch my tv settings..

Any idea why?

I recall that Xbox used NTSC-M black level (7.5 IRE) in 60Hz RGB mode, but don't remember whether that applied to component too. However, that resulted to washed out picture on a CRT instead of being too dark. Maybe your issue is that the display you have is set to limited range RGB instead of full which ossc is outputting.

Btw. I found out utitlity which dumps out (and allows modifying) highly technical detatils about Amiga's screenmodes. If there's any need, I can go through all modes and dump settings for you. Just let me know if there is.

It dumps out values in nS though, e.g. for HighGFX mode (which looks very cool BTW) it output values like this:

HScanFreq: 21.89 kHz
VScanFreq: 54.19 Hz
ColColock: 281.94 nS
Scanline: 45.67 uS
HBlank: 8.18 uS
HSync: 2.54 uS
VBlank: 913.48 uS
VSync: 274.04 uS
CSDelay: 264.04 uS

These details reveal number of scanlines outputted (21.89 kHz/54.19 Hz = 404), but lack pixel clock frequency which would be needed for calculating optimal H.samplerate. I guess there's a limited set of possible pixel clocks these special modes may use instead of a fully-programmable clock like in GPUs.

[jarp]

These details reveal number of scanlines outputted (21.89 kHz/54.19 Hz = 404), but lack pixel clock frequency which would be needed for calculating optimal H.samplerate. I guess there's a limited set of possible pixel clocks these special modes may use instead of a fully-programmable clock like in GPUs.

Not sure if pixel clock can be found from the user adjustable settings, there are sliders for "Total Clocks" and "Total Rows" in addition to sync and porch settings, but their values are integers which probably do not tell much unless you know how the monitor drivers do work? But does that even matter? When I output checkerboard pattern and fiddle with H. samplerate it is obvious for everybody which value is the correct. If it's off even by one, you get very noticeable vertical banding whilst when it's spot on then every single pixel is sharp as razor.