Pumping brightness/colors in 640×400@70Hz

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  • #13458

    So… this happens when I’m using the OSSC to process 640×400@70Hz VGA signals from my DOS PC:


    The picture is generally too dark; brightness and colors change depending on what’s displayed.

    This only happens when 384p processing is set to “Passthru”; in “Line2x” mode it doesn’t (unfortunately, not every monitor is compatible to “Line2x” mode). Likewise, it doesn’t happen if I’m forcing “Passthru” mode to output 1280×400 pixels by doubling “H. samplerate” and “H. active”.

    Other observations/thoughts:

    – The pumping isn’t in the VGA signal (otherwise “Line2x” mode wouldn’t help; also the pumping’s absent if I connect my PC and monitor directly).
    – The pumping can be observed on different monitors.
    – I’m positive this problem wasn’t there before. Everything that changed from my point of view was the OSSC’s firmware (0.77), so I tried downgrading to 0.76 and even 0.75. The problem persisted.

    What’s going on here?


    That’s probably caused by unsuitable clamp/ALC position or width for the mode.

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