Screen artifacts on 50Hz modeline

RetroArch General
#1

When I play PAL optimized games under a 50Hz modeline I get strange artifacts (not so on near 60Hz modelines). Not core related, I do get them on bsnes-balanced (Asterix, Tintin in Tibet) or Genesis Plus GX (Flink, Alien Soldier).

I was testing with a 50Hz modeline first, then for Sega Genesis I created a new 49.701 modeline. I revisited the 50Hz modeline to conform to LCD standard (CRU preset) but I get these artifacts on blinking sprites or big flat areas (resembles macroblocks, or unresolved h264 bframes). To be sure I disabled the shader and still get it so I recorded a video (link). The modeline works fine with other emulators like PCSX2, but this one is not full exclusive. So any hint on how to resolve it is welcome.

Shader artifacts on PAL refresh rates
#2

I just tested alien solider PAL and get the exact same effect in the same menu, and that’s on my gsync LCD monitor. It might just be the game.

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#3

I should test with an external emulator aside retroarch to check the issue on this game. I get another set of issues on 50Hz but are shader related mostly (reported here). I will do more tests tomorrow on that too.

#4

Ok, I tested with blastem stand alone and it also shows the issue, I also did some tests in retroarch for the shaders and it seems it all boils down to the modeline. When recording a video there are no issues.