[Question] Is Adaptive Sync possible over HDMI, or is it a DisplayPort thing only?

[vanfanel]

Hi there,

I'm using latest labwc stable version (0.7.1) on latest MESA on Alder Lake N100 (Minix 100-0Db, which has two HDMI 2.1 outputs available), with an Adaptive Sync / VRR / FreeSync compatible monitor attached via HDMI-A-1, identified by wlr-randr as:

HDMI-A-1 "ViewSonic Corporation XG2431 WEE233400018 (HDMI-A-1)"
  Make: ViewSonic Corporation
  Model: XG2431
  Serial: WEE233400018
  Physical size: 530x300 mm
  Enabled: yes

In labwc's rc.xml, I have this on the <core> section:

<core>                                                                                                                                   
    <reuseOutputMode>yes</reuseOutputMode>                                                                                           
    <adaptiveSync>yes</adaptiveSync>                                                                                                 
</core>

So labwc is trying to enable Adaptive Sync, but it fails to do so.
Looking at the labwc debug logs, I see this:

00:00:00.352 [backend/drm/drm.c:729] connector HDMI-A-1: Failed to enable adaptive sync: connector doesn't support VRR
00:00:00.352 [../src/output.c:930] failed to enable adaptive sync for output HDMI-A-1

I have been reading pages upon pages about Adaptive Sync, and I can't quite understand why is it failing to be activated here: it seems to require HDMI 2.1, but does it work on Wayland/WLRoots/labwc over HDMI, or is it a DisplayPort thing only for now? (I don't have anything with a DisplayPort connector to test and rule out the monitor...)

[johanmalm]

@Ph42oN - any thoughts?

[Ph42oN]

It works with HDMI too on my MSI G273QFW, i think it is older than 2.1 as refresh rate is limited to 144hz with HDMI. GPU is RX 6800, i don't really know much about intel GPU drivers.

Have you checked if its detected as vrr_capable on xrandr? (Must run on xorg, it will not show this on xwayland)

[vanfanel]

@Ph42oN is there antything I can do to test that on Wayland, please? I have no GNU/Linux sistems with X11 anymore, they are all self-configured with only Wayland libs etc

[Consolatis]

drm_info might provide further clues but I am not sure if its just giving the current state or is also showing VRR capability in general.

[droc12345]

For full 2.1, the adapter needs to support it, the monitor needs to support it and the cable needs to support it. If the cable doesn't pass the whole 2.1 bandwidth, then you won't get 2.1.

I don't know if that's your problem but an area to also check.
And on my monitor, I can do something like select the version of display port it uses.
You might check monitor settings.