AMD Enabling FreeSync Video Mode By Default With Linux 5.18, Merging AMDKFD CRIU

[Quackdoc]

Not sure what you are talking about, so pay attention please.

I'm comparing classic vsync (no adaptive sync) and adaptive sync. First one introduces latency to prevent tearing. That is clear I hope? I don't want to repeat the same thing needlessly.

there are three cases cases. this also assumes you are playing a relatively new game that turns of vsync when below fps. or are using vendor vsync (adaptive vsync on nvidia)

1. GPU can easily run the game past native speed / sync range
vsync limits refresh rate and introduces lots of lag
freesync does nothing no extra latency but it does nothing. you get screen tearing
freesync + frame cap minimal extra latency always works.

2. GPU can barely run the game at native speed / sync range
vsync will limit the game fps when possible (ads latency), or frame rate will dip below vsync and does nothing, you get screen tearing
freesync will work when in range (no latency), but will turn off out of range you get screen tearing
freesync + frame cap, will limit fps always works assuming stays within range

3. GPU cannot run the game at native speed / sync range
vsync nothing, no extra latency you get screen tearing
freesync does nothing, you get screen tearing without LFC
freesync + frame cap does nothing you get screen tearing without LFC

in none of these cases does freesync actively lower input lag. it does however when paired with a framerate cap, add far less input lag than vsync does. as seen in this video

https://www.youtube.com/watch?v=rs0PYCpBJjc

[shmerl]

Lag reduction by tearing vs. VRR is just miniscule, as is by shorter refresh interval when being well above 120fps. If game has idiotic CPU prerender of 3 frames (which many have), this is still ~12ms of additional lag even at 240fps. ~138fps with Reflex have lower total lag than uncapped 240fps with sh*t prerender. That's what those tests show.

Yeah, I'm not familiar with pre-render, so haven't compared that. I mean simply a scenario when the game tries to render as soon as it can but would wait if something is capped.

[shmerl]

...
2. GPU can barely run the game at native speed / sync range
...
in none of these cases does freesync actively lower input lag.

In case 2 with fixed refresh rate, vsync will force the frame to be displayed more than one refresh cycle, which still adds latency (the same frame will be displayed for two periods for example). Adaptive sync will change refresh rate itself to match the framerate. So the frame will still be displayed immediately when it's ready, just the period will be longer (i.e. refresh rate is lower). So the new frame will still appear sooner, because even that longer period is still shorter than two fixed periods.

[Quackdoc]

In case 2 with fixed refresh rate, vsync will force the frame to be displayed more than one refresh cycle, which still adds latency (the same frame will be displayed for two periods for example). Adaptive sync will change refresh rate itself to match the framerate. So the frame will still be displayed immediately when it's ready, just the period will be longer (i.e. refresh rate is lower). So the new frame will still appear sooner, because even that longer period is still shorter than two fixed periods.

older vsync implentations will, but most modern ones will just turn off when the refresh rate dips below that of vsync, so you will either get LFC kicking in if possible, or just plan old screen tearing

[shmerl]

older vsync implentations will, but most modern ones will just turn off when the refresh rate dips below that of vsync, so you will either get LFC kicking in if possible, or just plan old screen tearing

Yeah, that's what I'm comparing it to, that's why I sad it reduces lag. In comparison with classic vsync.

[Quackdoc]

Yeah, that's what I'm comparing it to, that's why I sad it reduces lag. In comparison with classic vsync.

I don't think anything has actually used that for a long time, any games from dx9+ are compatible with the new era of vsync so it's best just to use that, RIP OGL

[artivision]

Any actually useful information of how to use it with Mpv?

[shmerl]

I don't think anything has actually used that for a long time, any games from dx9+ are compatible with the new era of vsync so it's best just to use that, RIP OGL

Do you refer to something like enhanced sync by AMD? Never really tried it and I don't think it ever worked on Linux, so I think until I switched to adaptive sync monitor, all my vsynced games used the classic one. So I'm not sure what exactly do you mean by a long time in this sense.

https://www.amd.com/en/technologies/...e-enhancedsync



It would be nice to have that "enhanced sync" for range above adaptive sync though.

[Quackdoc]

Do you refer to something like enhanced sync by AMD? Never really tried it and I don't think it ever worked on Linux, so I think until I switched to adaptive sync monitor, all my vsynced games used the classic one. So I'm not sure what exactly do you mean by a long time in this sense.

https://www.amd.com/en/technologies/...e-enhancedsync

enhanced sync is just the new generation of vsync the abilty to automatically turn off vsync has been around for a while im not actually sure about OGL that joke was made in reference to enhanced sync though

[shmerl]

enhanced sync is just the new generation of vsync the abilty to automatically turn off vsync has been around for a while im not actually sure about OGL that joke was made in reference to enhanced sync though

OK, so how do you enable it? I always thought on Linux vsync is just the classic version of it (first in the diagram above).

UPDATE:

Looks like some suggest that using Vulkan mailbox presentation mode is equal to that "enhanced sync" logic.

So I guess that would mean:

MESA_VK_WSI_PRESENT_MODE=mailbox

But then how to do that for only above adaptive sync range?