Switched to pictures only (cover box and screenshot). Turned OMX back on. Thanks for the explanation.
Cheers

And it occurs to me that having separate core configs per content folder won't solve the Atari 8 bit problems, because this script modifies both the core options and the core's own config file in order to get to all the settings. hmm.

@dankcushions Yes I think that is what it looks like. But it's much easier to see in motion.
It's not related to the resolution (I tried several).

Report the issue here:
https://github.com/libretro/snes9x2010

Ok, I tried turning off dithering, and it didn't seem to make any difference.

I'm still getting artifacts, like echo-type sounds, sounds that go on longer than they should etc.

I have listened carefully to games that I am very familiar with on other systems, and this definitely only seems to affect Hatari.