MiSTer FPGA Forum

Heyas. I'm trying to track down the cause of very obvious ringing / fringing (what might be called sharpening artifacts) I observe on my MiSTer's analog i/o board component video output. The artifacts appear to the left of bright pixels in areas of dark->light contrast. Scroll down for photo examples.

I see the ringing on two consumer TVs (Sony, Toshiba) and a PVM.
Decreasing each display's "sharpness" setting to zero does not help. I have tried nearly all available menu and service menu settings on all three displays to resolve the ringing, to no effect.

Some consumer TVs perform unwanted signal processing, such as to increase picture "sharpness," and sometimes this can't be disabled. I think the fact that the exact same issue is occurring on the PVM rules that possibility out.

The PVM is interesting because it also accepts pure 15 kHz analog RGB. In RGB mode, with the same cable (the VGA to component RCA from MisterAddons), the picture is pristine; no ringing artifacts. Switch MiSTer and PVM to YPbPr and there they are again.

This past week I concluded the thin, slight-feeling MisterAddons cable was most likely at fault, asked around for a known-good one to try, and ordered it: a Monoprice VGA to BNC cable. I received it today and it exhibits the exact same artifacts. The Monoprice cable comes highly recommended by a CRT / video guru I know so I now doubt it is a cabling issue.

I reviewed all MiSTer .ini settings and none seem relevant. I disabled all post-processing filters in specific cores but to no effect.

What possibilities remain? So far I have:

• This is an inherent trait of MiSTer YPbPr, perhaps due to its 18-bit color output or whatever that oft-mentioned analog i/o board shortcoming is (seems unlikely).

• My analog i/o board is problematic somehow.

• My DE10-Nano is problematic somehow.

• My BlisSTer is problematic. Using BlisSTer instead of the usual MiSTer USB hub is the only unusual thing about my MiSTer setup, and BlisSTer is in fact a part of the AC power signal chain...

Image examples from Toshiba TV:

The opening text of River City Ransom (NES) readily shows the ringing / fringing to the left of bright pixels: Here's with the Toshiba's sharpening to max just to really bring out the artifacts lurking there: In this gameplay shot (pardon the CRT scanning) it's most apparent as the light vertical line to the left of the gray fence/bar: I can take photos from 240p Test Suite if anyone needs more convincing but trust me, the ringing is there. It just tends to be most obvious when the graphics are simplistic, such as in NES games and in MiSTer menu text.

I will be borrowing a friend's MiSTer to test with my displays / cables when I can. In the meantime, any other ideas? Thanks!

My money is on an issue with IO board.

EDIT: I have just realized that I can aslo use Component on my PVMs (Conversely to you & RGB), it's the same cable and same MiSTer after all. Never tried it before, but, after some tweaking of ini and removing EXT SYNC, it works:

As you can see these artifacts are not present.