Horizontal shift: am I doing it wrong?

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    Hi there!

    I’m experiencing a very odd occurrence, with the OSSC and my Japanese Mega Drive 2 + Mega CD 2 (it probably happens with all my other systems, but I’ll explain in a bit why I clearly notice it on the MD). It’s very minimal, so what I’m looking for is more like an explanation than a proper fix.

    Basically: as you may already know, many MD games came out with a colored overscan area (see this picture, in case).
    With the OSSC settings, without too much fiddling (as in, I don’t touch stuff like Sampling Phase or Sync Lenght, but only H-Backporch, H-Active and V/H-Mask), I’m able to crop the overscan out completely, in an apparently perfect and symmetric way (the mask covers up the very last rows of horizontal pixels top and bottom, and the very last columns left and right).
    Then I save my profile.

    Problem is: *sometimes* it happens that I turn everything on (I turn on the monitor > turn on the OSSC > leave it there if the last used profile is the one I need/if not I load it > set AV1 > turn on the console) and the image is shifted of one single pixel to the left. I can see – for example with Sonic itself – a 1-pixel pillar of blue pixels coming out of the mask. Some other times it’s fine at the boot-up, but it shifts if I load another profile and then come back to the Mega Drive-specific one.
    As I mentioned before, it probably does the same thing with all my systems, but I don’t notice it because usually the overscan area is black, so I don’t need to mask anything to begin with.

    It seems odd that it does that only on the H axis. V seems perfectly stable.
    I believe it’s the OSSC and not the display because I experience this little issue with both my monitors, an Asus VW246H (TN, 24″ and 1080p) and an LG 27MU67 (IPS, 27″ and 4K).

    Just for curiosity’s sake, I tried to touch up Sample Rate, Analog sync LPF… It may fix it the very moment I fiddle with them, but then – even after I save the profile with everything looking pixel perfect – it seems quite random whether or not it will still look like that next time I turn everything on again.

    Hope I explained myself well enough!
    Thanks in advance ^_-


    Maybe this is caused by the digitizer PLL2x bug because the symptoms are the same. Try to set ‘Allow TVP HPLL2x’ to off or use 320×240 optimized mode.

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