Custom Resolution Utility (CRU)

[ToastyX]

(05-13-2023 01:52 AM)XAGMNINETY Wrote:  Hi Toasty,

Been around here before, and you were very helpful. I ended up donating to this project at that time, as it's instrumental for the PCs that I have.

I've recently gotten HDMI 2.1 working on my LG OLED - previously, I only used it in HDMI 2.0 (with a 3080 Ti) as it was ran through an HDMI 2.0 Yamaha receiver. As a note, I used your application to remove all traces of the evil 4096x2160 - including one in the "HDMI Support" block that kept reappearing no matter what.

I wanted to make a quick note about this before my main question - in the "HDMI Support" block under the CTA-861 Extension block, the fourth entry by default on an HDMI 2.1 screen is a 4096x2160p @ 24 Hz. No matter how many times I removed it, this resolution would always re-appear after what seems to be an internal driver reset - perhaps the driver needs to see exactly 4 resolutions in this space at all times. What I did was "spoof" the 4th entry into a duplicate 3840x2160 30 Hz block, and that stuck. I was then able to load my proper DLDSR resolutions through the NV Control Panel. Not sure if that's a bug, but I figured I'd report it.

Anyway, I'm here to ask about refresh rate timings and how it relates to VSync stutter. Recently, I've been seeing games that are capped by the screen's refresh rate via VSYNC have a small but noticeable amount of motion and camera stutter - notably Left 4 Dead and Halo, two games notable for having very reliable frame time graphs. At first, I thought it was a driver issue, but I think it may come down to the timings I'm using for my custom resolutions. I've been using this tool (in a Chromium browser, Firefox is borked): https://www.vsynctester.com, and the frame time spikes it spit out, particularly on my laptop, have given me pause. I'd say every ~30 seconds or so in the best case scenario (OLED 120 Hz) and about every ~10 seconds or so in the worst case (Laptop 120 Hz), I get a big ol' frame time spike, large enough to span the entire graph of this test. These are results from either using the "Automatic" or "Native" options for PC, on 3 different machines.

Generally, I've used the "Automatic PC" or "Native PC" options, to try and find the right timings for the exact refresh. Early on, I tried to use the "Manual" timings to lock in the refresh exactly, but that seems to cause very frequent VSYNC stutter no matter what, so I quickly binned that idea and went with the Automatic or Native PC options. From what I can tell, "Native" is specifically tailored for 60 Hz intervals - that's why all 60 Hz options have identical values for both Native PC and Automatic PC. However, this is not the case for multiples of 60 Hz, as there is some variation. Is it wiser to use the "Native" option only for intervals of 60, or just 60 itself? I'm not really sure.

I've read the readme for the installation on the first page many times, as well as the "Timing Parameters Explained' page that details how the timings work, and I still am not really sure what the modus operandi is to find the most VSYNC stutter-free timings. I am well aware that each screen is (very) different and there's no silver bullet for any refresh rate, but I'd like to get as close as possible. It's not a huge deal on my OLED, as I have the BlurBusters GSYNC optimal settings enabled most of the time. But, as I mentioned, I do have a 240 Hz laptop that doesn't have a GSYNC screen that exhibits issues, and GSYNC is not a magic bullet for many games, particularly older ones, that weren't designed to run at arbitrary refresh rates. So this is something that will come up fairly often.

I am looking for high-level pointers, and nothing else, so that I can do these myself - I have 3 panels (1 OLED and 2 IPS) that all have different characteristics and there's no way I want to burden you or anyone else with any part of figuring this issue out. I'm also not looking for 100% perfection, either - especially considering a number of these refresh rates (90 and 75 Hz for example) are not direct divisors for the IPS Monitors I use them on (165 Hz and 240 Hz respectively). I'm essentially looking to minimize the stutter as much as I can.

Thanks for any advice you may have, and thanks again for developing this integral application. No rush on a reply, as it's by no means an emergency.

X

Timing parameters have nothing to do with stutter. Stutter happens entirely on the PC's end and has nothing to do with the monitor. Vsync is just a way to synchronize with the refresh rate, so the only way vsync can stutter is if some frames are missing the next refresh because they are taking too long to process.

One cause of vsync stutter is frame rate caps. Vsync already acts as a frame rate cap, so adding another frame rate cap can cause stuttering because it won't be synchronized with the refresh rate. I remember Doom 3 having this problem because it forced 60 FPS which caused nasty stuttering at 60 Hz with vsync on.

For games without frame rate caps, you'd probably get the smoothest result using a refresh rate that's below your average frame rate so the frame times are more consistent.

If something in the background is using up the CPU or causing disk access, that can cause frame time spikes.