Snes screen distortion on top of the screen

[WasherFace]

I’m not sure if this is the dreaded SNES Jitter issue that’s already been documented on this forum, because I haven’t been able to find a video of it in action. This video shows that the top-middle of the screen jitters noticeable on the top letters the most and it does not show up on my CRT tv. No other console that I have has this issue on the OSSC Pro so really I’m not sure what to do. The SNES is being plugged in directly with the HDRetrovision Component cable to the OSSC Pro but I also plugged in using the SCART cable and the same thing happened. It can be remedied by using optimized sampling and adjusting the phase but that doesn’t help in 512 wide games.

here’s the video

[Zacabeb]

The recommendations on the OSSC wiki suggest that reducing H-PLL post-coast to 1 can help the H-PLL recover faster to remove the jitter. If it needs to be set higher and the display doesn’t like the output, using scaler mode and turning off framelock can help.

https://junkerhq.net/xrgb/index.php?title=Super_NES

[marqs]

SNES jitter is indeed the root cause, but you can increase H-PLL Loop gain to compensate:

https://junkerhq.net//xrgb/index.php?title=OSSC_Pro#H-PLL_Loop_Gain

[Zacabeb]

@marqs It seems the info about the SNES on the wiki contains an error, suggesting to adjust coasting rather than loop gain (I had a feeling there was something off.)

[marqs]

The coast instruction is valid for original OSSC from which wiki the snippet is from. It can help with Pro too but loop gain adjustment is more effective. The chip in original OSSC uses analog PLL where loop characteristics are largely defined by the external components on the PCB.

[WasherFace]

Thanks you guys this solved my issue!

[lyrical]

It seems the info about the SNES on the wiki contains an error, suggesting to adjust coasting rather than loop gain (I had a feeling there was something off.)

I suspect there to be this mistake too.

The text quoted below describes exactly what happens when I increase Loop Gain. Post-Coast set to 1 would be a decrease from its default value on the OSSC Pro (4). A Loop Gain of higher than 1 indeed breaks compatibility with my capture card, while Post-Coast even at 4 does not. (And Post-Coast is supposed to be decreased to zero in the OSSC instructions.)

PLL bandwidth can be increased via “AV1-3 sync opt -> H-PLL Post-Coast“. Usually value 1 is enough to clear the jitter while preserving display compatibility. With higher values framelock may need to be disabled to ensure display can sync with the signal.

• This reply was modified 4 months, 2 weeks ago by lyrical.

[marqs]

Yeah, there was an error in wiki but it’s now fixed. Post-coast reduction should not be necessary with Pro and will just break compatibility with some other sources (Taito F3, certain Amigas etc.).

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