"Ghost frames" while playing on medium-heavy titles

[rickythewoof]

Description

Hello, as the title suggests i'm having some trouble with "ghost frames" of some sort. The issue is very weird, especially when going through a heavier load (like vrchat) I can see that "old frames get added between legitimate frames".
Oddly enough, I don't see any dropped packets in the statistics of alvr dashboard, and if i try to see the VR view it's absolutely fine. While trying to record the statistics of alvr I could weirdly see the exact same issue in the recording of it, which i'll include. The video shows basically exactly the same kind of problem I see while playing in vr through the headset.
I'm pretty sure it's not an issue of my rig being too weak, because Windows 10 works without issues of sort.

Here the video:
https://github.com/user-attachments/assets/f71a398a-bbf6-4177-a453-7cd9b74725a1

General Troubleshooting

• I carefully followed the instructions in the README and successfully completed the setup wizard
• I read the ALVR GitHub Wiki

Environment

Hardware

https://linux-hardware.org/?probe=038c333980

Headset:
Pico 4
CPU:
Ryzen 7 5700X3D
GPU:
Nvidia Geforce RTX 4070 Suer
GPU Driver Version:
565.77
Audio:
Pipewire

Installation

ALVR Version:
tested 20.12.1 until 20.11
ALVR Settings File:
session.json

SteamVR Version:
Latest stable, Steam installed through RPM, tested beta around a month ago with the same issues

Install Type:

• Packaged (exe, deb, rpm, etc)
• Portable (zip)
• Source
• Used Launcher to install the alvr dashboard

OS Name and Version:
both Fedora 41 Workstation and PopOS 22.04 (Wayland and X11) have this same issue, windows doesn't

[shinyquagsire23]

This miiiight be the same issue as #2636 ? Does it show up with streamer 20.11?

[rickythewoof]

From plyshkan on ALVR's DIscord server

this is basically what happens on steamvr on linux
it can't reproject under < half framerate at all
and even under more than 45 it fails to do so
valve did not provide linux steamvr with direct mode so we could just reproject on client instead, so there's that
only way to avoid this - stay above half framerate and enable legacy reprojection under per app video settings
but be wary this will significantly increase load on cpu/gpu
other way to avoid - to switch from alvr to wivrn, which doesn't use steamvr and own monado runtime instead

Using wiVRn completely fixes it for me. Unfortunately, it's not a viable option since I have multiple add-ons and (biggest of them) slimeVR which hasn't a way to connect directly the trackers to it.
Until we have some sort of reprojection only thing i can do is to heavily limit graphics and/or enable legacy reprojection

[The-personified-devil]

Potentially, but as Shinyquagsire said, we currently also have an actual bug with pretty much the symptoms you're describing, so just checking if it also occurs in the old version would be helpful to isolate whether it's that bug or steamvr reprojection.

[rickythewoof]

Does it show up with streamer 20.11?

As stated in my original post, I had tried the 20.11. I tried that version again right now, unfortunately it still gives me exactly the same issues. Also, enabling Legacy Reprojection doesn't work for me, it's a tad bit better but still it has the same issues.

[EpicGazel]

Potentially, but as Shinyquagsire said, we currently also have an actual bug with pretty much the symptoms you're describing, so just checking if it also occurs in the old version would be helpful to isolate whether it's that bug or steamvr reprojection.

This issue exists on Linux Mint as far back as v20.7.1 (Oldest 20. version I could run that would still connect to steamvr). Issue does not happen with WiVRn v0.22.
Quest 2 - 5700X3D - RX 6800XT

Non-comprehensive summary of attempted fixes:

• SteamVR beta & previous branch
• Proton Hotfix, GE-Proton9-23, GE-Proton9-22-rtsp17-1
• Software encoder, software decoder (black screen)
• ALVR Nightly, ALVR v20.7.1, v20.8.1
• Setting client framerate to 90 or 120 using sidequest
• Setting server framerate 72 to match client
• Disabling all other overlays and addons
• Reducing resolution to low values (effective in reducing GPU load and thus the issue, but quality obviously suffers)
• Reducing and increasing bitrate
• Wired connection
• Performance CPU governor
• gamemoderun
• VRChat --disable-amd-stutter-workaround
• AMD GPU Power profile "Virtual reality"
• DXVK_FRAME_RATE=90 (locking framerate)
• Disabling steam overlay
• PR (feat) Improve frame pacing, and only go framepaceless if the GPU is loaded #2642 both individually and cherry-picked onto master (did potentially help some hitching but not the ghosting)
• Changing maximum buffering, enforce server frame pacing, adapt to frame rate, UDP and TCP
• SteamVR Debug command (async toggle unlocks it from 45 fps and may help in some scenarios but isn't the fix)
• Bios tweaks (disable: FTPM, AMD Cool & Quiet, CPPC Preferred Core, High Precision Event Timer)
• Using https://github.com/GPUOpen-Drivers/AMDVLK for game (VRChat would boot when enabled in launch options)
• Variations of single monitor of varying refresh rates and ALVR varying refresh rates
• VRChat Specific: Disabling "Personal mirror", this has a notable impact on GPU headroom. It seems to especially effect culling efficiency (try looking at a wall). Also, disabling this more or less removes the "Display Error" (purple) lines from the SteamVR performance graph.
• "enableLinuxVulkanAsync" : false in steamvr.vrsettings
• SteamVR Legacy Reprojection in per application settings (no noticeable difference)

Upon deeper research, this may be an ongoing issue with SteamVR-For-Linux that may have Mesa implications. See:
ValveSoftware/SteamVR-for-Linux#613
ValveSoftware/SteamVR-for-Linux#631
ValveSoftware/SteamVR-for-Linux#685
ValveSoftware/SteamVR-for-Linux#230

ValveSoftware/SteamVR-for-Linux#633
Mesa (fixed?):
https://gitlab.freedesktop.org/mesa/mesa/-/issues/10101