[Bananmos]

Ah, of course… I forgot about the half-scanline in interlaced mode. Silly of me!

In theory, I suppose the OSSC *could* buffer half a scanline and have the output frame rate be 265.5/262 of the original, in order to support higher scaling for interlaced… sort of how the Hidef-NES manages to compensate for the original signal’s line rate being different to the output. But that would be a lot to ask for a mode that’s going to look pretty rubbish no matter what… 🙂

Unfortunately, changing H-PLL 2x setting didn’t help either. But I’m now pretty convinced it must the shorter scanline causing all this, and will patiently wait for Marq’s hardware mod to be available.

But thanks for all the advice Paul!

[Bananmos]

Hi, and thanks for your response.

The H-PLL Pre-Coast/Post-Coast are set to 1 & 0, and I’ve tried to increase Analog sync Vth until it loses sync, with no noticeable improvement in picture loss.

> Does the OSSC lose sync though when you lose the picture?

Hmm, doesn’t look like it. The main menu keeps displaying “AV1 RGBS 262p / 15.74kHz 60.08Hz” even when the picture disappears.

I tried your recommendation of 480i, but actually made Super Mario World run in interlaced mode on my SNES Powerpak, using the game genie codes from http://www.hdretrovision.com/blog/2016/12/29/super-mario-world-in-480i

But I’m a little bit unsure of what settings the OSSC should use for this kind of test? To start with, there doesn’t seem to be any way to keep the 5x scaling when running SMW with those Game Genie codes. Instead, the OSSC will automatically switch to a 480 mode, which is dependent on the “480i/576i proc” setting.

And I get the following results for the different settings
“Passthru”: Picture is stable, and my HDTV says it is “480i”. I get no loss of picture
“Line2x (bob)” Picture is looking very flickery and shimmering, but I guess that’s as expected from an interlaced signal? HDTV says it is “480p”. I get no loss of picture.
“Line3x (laced)”: HDTV won’t accept it – Just says “out of range”
“Line4x (bob)”: HDTV won’t accept it – Just says “out of range”

So I guess I’ve done the supposed test then? But I am a little bit surprised that the OSSC forces a line-doubling mode here, rather than staying at the 5x setting I chose for 240p. But I guess it’s as designed.

[Bananmos]

So according to marqs (the mod board author in the thread at https://shmups.system11.org/viewtopic.php?uid=11668&f=6&t=61285&start=0), there is one difference with the SNES compared to the NES:
“The short scanline actually occurs deeper in vblank”

But it seems odd that this would be the cause of the SNES@60Hz not working on my TV while the NES works perfectly. So I’m still not convinced this is the problem in my case.

Nevertheless, another thought I had regarding the odd/even frames problem… as the OSSC does a bit of buffering already, shouldn’t it be possible for it to buffer just enough to be able to smooth out the odd/even frames into frames with consistent timing? If the OSSC can generate output sync at 2x the pixel clock rate of the NES/SNES PPU, a frame_clocks+2,frame_clocks,frame_clocks+2,… sequence at the input should just equal frame_clocks+1 at the output.

I know this might complicate the FPGA code in order to support just two very quirky systems and may not be top of the priority list for new OSSC firmware. But if possible, it seems like a better alternative than asking people to do yet another complicated hardware mod to their SNES/NES consoles…

[Bananmos]

Doh! Nevermind… tested it today and it looks like it was just my small CRT’s SCART input being a bit glitchy. Silly of me not to check. But good news is my SuperCIC mod seems to work perfectly! 🙂

Less good news is that the SuperCIC mod did not fix the video dropouts in 60Hz that my TV was showing with the OSSC on old quick’n’dirty 60Hz-enabled 2chip console. As the 2chip was outputting 59.53Hz in NTSC rather than 60.08Hz, I was blaming the dropouts on this. But it looks like something else must be causing them…

[Bananmos]

Careful! If you attach an original PAL region SNES PSU to a Japanese or American console you will fry it, since these PSUs output AC rather than DC.

Yes, I’ve read about the Famicom and SFC not being compatible due to expecting DC. But it is news to me that an american SNES would be problematic too. Are you sure about this? It surprises me, because to my knowledge PAL NES power supplies and PAL SNES power supplies have been interchangeable between my PAL NES and PAL SNES units, and have also worked fine on NTSC NES consoles.

But looking closer,the french adapter (with the slightly different form factor which does fit the 1chip console) does have slightly different ratings:
MODEL NO NES-002ED
INPUT AC 220V 50Hz 17W
OUTPUT AC 9V 1.3A

Whereas my other NES adapters (that I have been using for loads of years with both NTSC and PAL NES consoles, and with my 2chip SNES console) says:
AC ADAPTER: NES-PAL-002
INPUT: AC 220V-230V/50Hz
OUTPUT: 9.8V 1.3A

And finally, an authentic US NES power supply I own (which I’ve never actually plugged in to anything) says:
MODEL NO : NES-002
INPUT AC 120V 60Hz 17W
OUTPUT AC 9V 1.3A

…so assuming there’s no rounding error in the printed specs, I guess the french NES power supply outputs a slightly lower voltage than the standard?

I also found a photo of an official UK SNES power supply. Interestingly, the console-side-plug has the same blue colour that the french power supply with the alternate form factor also has, but is rated at 9V output like my other power supplies:
http://www.ebay.co.uk/itm/Official-NES-SNES-Super-Nintendo-Console-UK-Mains-AC-Power-Supply-PSU/202112457157?hash=item2f0ed759c5:g:Gg0AAOSwxixaH–1

I am considering getting an RGB amp just for completion. But I am wondering whether I will actually gain anything from it, and it doesn’t look like a trivial mod. The cheap RGB cable makes my assessment somewhat limited, but I’m not so keen on ordering a proper packapunch cable for PAL, if it is not at all usable if the RGB amp mod is done. Is there any way to adapt the RGB amp to a cable wired for PAL?

Anyway, the 1chip SuperCIC parts still seems to be out-of-stock. Any idea on when they will be available again?

Cheers,
Michel

[Bananmos]

So my 1chip arrived! It was a console without a power supply, and initially I was quite frustrated when realising that a very slight increase in the AC adapter socket made it incompatible with all my NES/SNES AC adapters… except for the one I bought with my french NES, which plugged in just fine due to being just slightly thicker (works with the usual NES/SNES consoles too, but wiggles a little). This minor difference in the AC adapter pins sure is a curious thing.

Anyway, the picture from the OSSC now looks pretty amazing! It is quite bright, so would benefit from the brightness fix I suppose – but at the moment I’m not too bothered by the brightness, just being impressed with the pixel-perfect 5x image coming out of the OSSC. The colours do have that ugly composite checkerboard patterns – but this should all go away once I replace my cheap RGB cable with a packapunch one.

But given how great the picture already looks with the OSSC, I’ve started wondering whether I actually need the RGB amp, or if I’d be fine just with the SuperCIC mod itself.

Looking at the picture that explain the advantage of the RGB bypass amp, it seems that the main advantage is getting rid of a pixel blur of the 1chip. A blur that looks way less severe than on a 2chip, but is still present.

And I can definitely see how it would improve the picture in the standard 4:3 mode, given that the amount of samples the OSSC takes would likely be capturing part of this lowpass curve between pixels.

But assuming that the 256×240 optim mode is enabled, the signal should be sampled at the centers of the PPU pixels – provided that the sampling phase has been adjusted accordingly, and because the blur is not as severe, perhaps the RGB bypass amp is just overkill if using the OSSC?

I’ve read that the RGB bypass amp should also help with the bright vertical line in the middle of the screen… and I remember this ugly vertical line from my youth when playing the SNES with just an RF cable. But I cannot see it at all from the output of the OSSC when trying it out this one-chip with SMW or any other games… it could be that the composite colour artifacts are hiding it a bit. But even when fading between black and white screens, I cannot observe any bright vertical line no matter how hard I look…

So if I intend to use the SNES with OSSC set to the 256×240 optim mode, is there actually any advantage to the RGB amp that I’ve missed?

Or am I better off just getting a SuperCIC board, and a decent (PAL) sync-on-luma RGB cable?

[Bananmos]

BuckoA51:
Cool, thanks for letting me know that’s a complete list of parts. And had totally missed that PAL minis don’t even exist – oops 🙂

Well, the reverse LPF does “work” on my console, in the sense that it does something. There are just no settings that will actually improve the picture overall. A work colleague of mine who just got an OSSC seems to have had a lot more success with his 2chip SNES though, so I guess different 2chips must be slightly different. I’ve updated my “SNES issues” thread with the comparisons: https://videogameperfection.com/forums/topic/snes-issues/#post-17543

Anyway, have just bought a newly listed 1chip for just under £60 now, so with a bit of patience and modding I should be able to enjoy a crisp SNES video output on my OSSC soon enough. 🙂

[Bananmos]

So a bit of an update on part of my questions: A work colleague of mine with a 2chip PAL SNES got an OSSC, and tried the reverse LPF (in Line4X mode), and the result wasn’t perfect but looks kind of ok: https://photos.app.goo.gl/NHTarHUVkSCV0ibf1

I then borrowed his Packapunch sync-on-luma RGB cable to test the theory of whether my cheap cable could be making the reverse LPF perform worse than expected. And while there was a noticeable improvement in video quality (solid colours instead of checkerboard patterns) the reverse LPF seems to behave the same as before, with no settings being able to make it look much better. Here’s some close-ups in Line5X:
90 degrees sample phase: https://photos.app.goo.gl/ZEA1r5BhIwlzm5e73
180 degrees sample phase: https://photos.app.goo.gl/s0NVeR9mnZcVKOfJ3

So I am now fairly convinced that there must be quite a variation of the amount of blurriness applied for different 2chip consoles.

[Bananmos]

t raising the “Analog sync vth” value found under “Sync opt.” worked out for me. I set it to 169 mV and the sync stayed stable.

I brought it up to 270mV (higher values would drop the picture completely) and it would still lose sync. The sync loss behaviour is a bit intermittent though. Often when I boot my SNES powerpak up, it won’t even stay for more than a few seconds. But more commonly, it’ll lose sync every minute or so. But if you got a real Super Famicom rather than a PAL console with a 60Hz switch, I think you’d be fine with my 40″ TV – it works well in 50Hz mode after all.

The photos of 256×240 with reverse LPF look like you didn’t tweak the sample phase perfectly. Set reverse LPF to 4 and tweak sample phase some more.

I have tried lots of combinations of LPF and sample phase, but no setting seems to do it. (although some do make 256×240 optim mode look a bit more pleasant) Here’s an LPF setting of 4 and two different values for the sampling phase:
90 degrees: https://photos.app.goo.gl/9RgUVY8Rg5nCtMCw1
258 degrees: https://photos.app.goo.gl/r54qL723Irm3edAL2

I am a bit surprised why some people report such success with the LPF filter though… looking at the forums, I see screenshots that seem to completely remove the blur. So I am wondering whether my lack of success is just a case of different 2chip models having different amounts of blur?

Or could it be the cable interference making the problem worse? (increasing LPF to max did sharpen the intensity of the composite checkerboard pattern in solid colours as well)

Or yet another setting I haven’t considered? I did try the various settings mentioned in the firmware update thread… but the reverse LPF would still not give great results… just a dimming of the blur at lower settings, and a brighter edge after it at higher settings.

// Michel

[Bananmos]

Can you post a closeup picture of the bright edges that you see? It might be fixable. Did you try it on every lineX mode?

I only tried it in 5x mode, but when trying other modes now I’ve come to the conclusion that the latest firmware update caused the OSSC to have fewer modes working on my 40″ SONY TV… 🙁

Trying in 50Hz:
In Generic 4:3, only 2x and 5x work
In 256×240 optim, only 5x works

…though don’t take this firmware-gone-worse-claim at face value – it might very well be some other change I missed, although I did do “reset settings” before trying the various modes. I’ll try to find some time to in the weekend to go through all the steps and/or firmware comparisons and see if I can confirm exactly what went wrong.

For now – since the filter only makes sense in 256×240 optim mode AFAIU – I’ve taken 3 closeups at 5x in 256×240 optim mode, with a reverse LPF setting of 0, 15 and 31

0: https://photos.app.goo.gl/NbkIhM0TElosD1fX2
15: https://photos.app.goo.gl/wzWF22JoMeulM7hP2
31: https://photos.app.goo.gl/i2acsD0kLSRTgyVl2

What kind of RGB cable are you using? Composite video sync, luma or sync stripper?

The straight answer is I don’t really know 🙂 – But I did read up quickly on this, and think I get the difference. Given that my colours have a very distinct checkerboard pattern to them, and that the cable inside is just a bunch of wires and some resistors ( https://photos.app.goo.gl/wzFd2iMnKDL0rlSC3 ), it sounds to me like it’s a composite video sync one rather than the cleaner sync-on-luma and sync-stripper variants you mentioned?

I noticed there were two cables sold on retrogamingcables.co.uk, which I assume are sync-on-luma and sync-stripper, from the description?
https://www.retrogamingcables.co.uk/super-nintendo-pal-rgb-av-scart-cable-lead-cord-for-sale
https://www.retrogamingcables.co.uk/SUPER-NINTENDO-SNES-PAL-RGB-SCART-COMPOSITE-SYNC-CSYNC

From a quick skim-through, it sounds to me like the more expensive sync-stripper one should have has better compatibility with more displays and would be worth paying extra for? But is there any downside to it? It does sound like a wise thing to invest in one of these cables… although I am starting to worry if there’s yet more model differences I’d need to consider here, depending on if I get a replacement 1-chip NTSC/PAL SNES of a particular model? (as this has already opened up a rabbit hole of SNES tech stuff… which is kind of fun to learn, as long as there’s luminance at the end of the video tunnel… 🙂

Thank you very much for the link, I’ll be on the lookout for those serial numbers… My own 2-chip is “UP10895189”, which predates any others in the PAL chart. Although I’m not sure how useful that would be to add to the spreadsheet anyway, as it clearly predates all the other confirmed 2-chip SNES consoles…

// Michel

[Bananmos]

Thanks for that link Harrumph! Looks like another one of Chris’s great pages that I somehow missed 🙂

So that page pretty much tells me there’s no way the OSSC could get a pixel-perfect video signal for the 2-chip SNES, given that the blurry falloff is about a pixel large.

I do understand that the sample period needs to be delicately aligned to sample at a stable point. It’s just that I was convinced the OSSC was having problems with the shorter scanline, which seems to have been a red herring.

I did just try the new LPF feature, and it doesn’t seem to help at all with my SNES. Just gives me bright edges instead (as someone else has already reported). Guess it only works on less blurrier models…

Out of interest, I note that Chris’s page only checked the output from the cable. But I assume it’s been confirmed that the slow colour change is a property of the internal PPU circuitry, and not due to any discrete components on the board which could be replaced?

Anyway, I guess getting a 1-chip SNES is the only way to really use the OSSC with a SNES at this point. 1chip consoles do seem quite a bit pricier than the standard (unidentified) ones going for sale. The brightness fix seems like a trivial mod though, so that shouldn’t be a problem. And it looks like the ghosting just needs replacing a surface-mounted resistor as well?

Is there any web store that sells ready-made SuperCIC 1chip SNESes? eBay.co.uk does seems to have loads of SuperCIC-ready SNES models for sale, but they don’t mention whether it’s a 1chip, so I’d assume not.

Is there any definite verdict about which SNES/Famicom is better? The 1-chip version with the original look, or the Mini/Famicom Jr variants?

BuckoA51: Is that a mod for the 2-chip SNES? Any possibility to say anything more about it at this stage, or a possible announcement date? 🙂

And thanks for your input people, it’s really appreciated! I know way too many technical details about the NES, but my SNES knowledge is very limited so far. I was so close to ordering a Famicom on eBay, which would likely have been just another console with blurry output…

// Michel

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