Trying to understand various custom resolutions esp. reduced blanking - XL2540

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Trying to understand various custom resolutions esp. reduced blanking - XL2540

Post by Felicity » 25 Feb 2020, 17:16

Hello there blur buddies,

after being recommended CVT Reduced Blanking as an option to clear up the display and, by extension, more easily distinguish input latency and display latency since my eyes only seem to get worse over time and fast motion gets harder to distinguish, I am trying to understand exactly what I am doing when I am changing these settings, and what their benefits can be for gaming (in particular, fast games with lots of turning like Overwatch and potentially Project A upcoming).

For the sake of frametimes, I will be asking regarding 1280x720- not 1920x1080, which does not seem capable of easy setting of reduced blanking. Running the game at 720p not only helps my frametime stability (not really an issue on 1080p either, but any bit can be even stabler) but makes this easier, so we will use that for now.

Using NVCP and not CRU (Since it has default values for reduced blanking and I cannot really understand what I am changing in CRU exampli grati this thread), the automatic values are this, at 240hz on a 2540 using 441.41 nvidia drivers on windows 8.1. AMA on premium, instant mode on.

Automatic defaults

CVT Reduced Blank

Now, I can of course read numbers, and can see the difference in total pixels. I can assume less pixels especially since the active pixels in reduced blank match the resolution *exactly* is probably already an improvement. What I want to understand is what exactly changes with the other options. I have done some surface level research, but found little on the specifics of differences. Additionally, I'm aware that when using blur reduction, you want a larger vertical total, and not a smaller one. To clarify, I am not using blur reduction or gsync compatible/freesync. I have tested it, but sometimes it is hard for me to tell placebo or not.

What confuses me is, specifically: how does blanking affect game rendering? Is reducing it worthwhile or does it cause problems?

Active pixels go from 1024 vertical to 720.

the front porch and sync width are significantly less. What does that incur? What benefits does it have? I am sure I could do some more research on the differences in these values and their pros/cons, but sometimes the technical knowledge goes over my head.

Total pixels are significantly less (I guess reduced means reduced). I assume this is a result of a formula considering the other values are changed.

In particular, though, the polarity is swapped. What does that mean? With a reduced vertical active pixel total, does that mean the vertical polarity should be negative rather than the horizontal? Am I incidentally adding input lag by swapping these, or not having them on ++, or perhaps missing out this entire time on +/- being better?

What defines the need for these polarities?

If there are good sources for the answers to these questions, forward me there. Otherwise I would be very happy if someone could explain these differences to me and what they result in, whether I am actually hurting myself by using reduced blank or if I should have been using it this entire time on a slightly lower resolution.

Thank you,

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