OSSC problem black empty output from C64 svideo signal via Sony S-RGB transcoder

[Nrg]

Hello,

I have Commodore 64 svideo output connected to Sony S-RGB transcoder, and the RGB SCART output from Sony transcoder connected to OSSC AV1 SCART input. The problem is OSSC detects the input signal, but output is totally black/empty. Any idea what might be causing this? Connecting the Sony transcoder directly to TV using RGB SCART works OK, so the problem is related to OSSC..

Bad: C64 svideo -> Sony S-RGB SCART -> OSSC -> TV.
Good: C64 svideo -> Sony S-RGB SCART -> TV.

OSSC reports the following information about the signal from C64 via Sony S-RGB transcoder:

AV1: RGBS 311p
15.63kHz 50.27Hz
VMod: 288p
LO: 624 VSM: 0

Svideo -> RGB SCART Transcoder is Sony S-RGB YR-3000.

I’ve tried setting the OSSC H-PLL pre/post values to 4, and Analog Sync LPF to 2.5MHz (as instructed on http://junkerhq.net/xrgb/index.php/C64), which made the OSSC LED turn from red to green, but still the OSSC DVI output is totally black/empty.

Samsung TV detects the OSSC DVI output as 720×576 @ 50 Hz, but like said the image is totally black/empty. Dell PC monitor (U2311) also detects the OSSC output as 720×576 @ 50 Hz, with the same symptoms, screen is all black/empty.

I also tried connecting OSSC DVI output to Extron scaler, which reports the OSSC signal as “576p @ 50.12Hz”, which is a bit weird, considering OSSC says 50.27Hz.. video is all black/empty in this case aswell. So it seems OSSC is really sending empty signal for some reason..

Any ideas? Currently OSSC in question is running v0.69 firmware.

[afangus]

Does the led of the ossc is red when C64 is plugged in?
Do you use X2 or X3 line mode ?

[Nrg]

Yes, after changing the H-PLL values the led changes to green.

I’ve tried both X2 and X3 line modes, but the end result is the same with both; output is all black/empty.

[paulb_nl]

Does another console work through the transcoder?

[Nrg]

I don’t unfortunately have other “consoles” atm here. But like said, if I connect the transcoder directly to TV using RGB SCART, it all works fine!

[paulb_nl]

If you test another device with the transcoder then at least we know if the C64 or the transcoder is causing this issue with the OSSC.

[Nrg]

Thinking more about it.. actually I do have an Amiga here. So I connected Amiga composite video output to the Sony S-RGB transcoder, and the Sony RGB SCART output to OSSC. Same problem, OSSC detects the signal correctly (49.92Hz refresh rate etc), but the video output is all black/empty..

And if I connect the Sony transcoder directly to TV using RGB SCART, the TV displays the video just fine, no problems there..

So it seems OSSC is somehow incompatible with the Sony S-RGB transcoder.. because it fails with both the C64 and Amiga signals. Any idea what might cause that?

[paulb_nl]

I am guessing that you get a black screen because there is no signal on the RGB pins. Are you sure the TV is displaying a RGB signal and not just composite/svideo through the SCART connector?

[Nrg]

That got me thinking.. and that was spot on. I have multiple SCART cables, and I was accidentally using the one which doesn’t have RGB pins wired up.. so the TV was displaying composite video, and OSSC was only getting the sync signal, no RGB video.. aargh, I feel so stupid right now 😀

So mystery solved.. after changing to proper RGB SCART cable and I can now see the actual video thru OSSC, in both X2 and X3 modes!

Thanks a lot and sorry for being stupid. Sometimes the solution is too obvious..

[BuckoA51]

While we’re here, can you try a C64 title that has a bright white screen? I’m having problems in my setup with this, which is using exactly the same transcoder as you.

[Nrg]

Yeah, it seems I have the same problem. After all-white screen on the C64 signal OSSC display shows really weird values for a while until it stabilizes again.. I assume the Sony transcoder gets confused for some reason..

[BuckoA51]

Getting flashbacks to the XRGB3 here!

[Nrg]

I wonder if those “white-issues” are related to the fact that C64 is known to have “too high” analog levels in the svideo output? That’s why one needs to have extra resistor in the circuit.. so even more attenuation is needed perhaps?

[marqs]

Does that happen if you plug composite video to Y-input of OSSC component connector?

[Nrg]

I just tested that (plugged composite video from C64 to Y-input of OSSC), and that works fine. The all-white scenes don’t cause any kind of trouble.. so that means it’s the Sony transcoder that gets messed up ?

If someone else wants to test aswell: I used a demo called Comaland (by Censor Design and Oxyron) for C64 (http://csdb.dk/release/?id=133940). You can see the issue after around 2 mins when running the first floppy of that demo (image1.d64).. there’s the scroller with all-white background, which totally messes up the sync/signal when using the Sony Transcoder with OSSC (OSSC display shows all kinds of weird signal infos during that time period and you lose the video).

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