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

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  • #41
    Originally posted by shmerl View Post

    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).


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

    So I guess that would mean:

    But then how to do that for only above adaptive sync range?
    that is more like fast-sync on nvidia, better known as triple buffer vsync. which is vsync where the back buffer is always being updated with a fresh image. it results in low latency for vsync, but still more than none. however since GPU controlls freesync, it shouldn't add extra latency, or any at all when used with adaptive sync. but I haven't seen any tests for that.

    as for turning of v-sync automatically. it's just kind of been a thing. you can test it yourself with strangle and opengl just limit below the vsync threshold and see if tearing happens. I think game engines control it.

    as a side note you should checkout latencyflex if you haven't already, it's pretty cool

    EDIT: with tripple buffering or VK mailbox, the added latency is just the screen refresh time. so effectively if the screen wasn't to tear, but without vsync delay. so ti should be fine 99% of the time


    • #42

      Originally posted by RejectModernity View Post
      From a usage perspective, this isn't actually Freesync. :-)

      It's more: Using the freesync capabilities of the hardware, create extra "virtual" video modes with fixed refresh rates that match common movie (video != video :-) ) modes. A movie player like KODI could then for example change video mode to exactly match the framerate of the movie for every movie. (And it says that the change should be flicker free).


      • #43
        Originally posted by RejectModernity View Post
        You're not supposed to put it in your mouth you silly goose, it's for monitors.
        You do not say big silly goose. You call him an asshole like a normal kid.


        • #44
          I don't get it. Is this parameter to be passed to the kernel by the bootloader? I still included it in 20-amdgpu.conf a long time ago and haven't seen any other manuals.


          • #45
            So is this feature limited to specific GPUs or are all Freesync capable GPUs included? I'm still not able to turn on Freesync on my Vega (2400G).

            I don't consider syncless (tearing) to be better because you only get one half of the picture displayed without delay and the next half with one full frame of delay.
            In contrast classic Vsync gets you anything between full frame to no delay depending on when the frame is ready.
            With Freesync you get the full picture with minimal possible delay because you don't need to wait for your next Monitor refresh cycle.

            Whats more of a problem is that the GPU takes different time to compute each frame (depends on complexity) resulting in stutter (varing time between physical state of engine and frame display) that you can't mittigate with any of the above methods. Its purely an engine/gamedev problem to ensure that each frame takes the same compute time. Vsync amplifies that problem and therefor everyone thinks the other methods reduce stutter, no they just don't amplify it.

            On consoles they allready try to get constant compute times mostly by delaying fast frames but it would be better to know the complexity of an upcomming frame and reduce it with shortcuts like lower resolution or coarse shaders (wich also is beeing used on consoles).
            Atleast for me a few frames beeing off is more disturbing than a constant delay to wich one can adjust.


            • #46
              How is this different from 5.13? Didn't 5.13 bring Freesync over HDMI?


              • #47
                this is great but the bigger question is, will gnome finally support freesync in wayland by the time 5.18 comes out?