"WARNING Desync detected. Attempting recovery." With OpenVR "simple controller" example driver and Phone VR app.

[KelvinGuy1]

I am developing drivers based on valves simple controller driver. When attempting to run this driver with ALVR and Phone VR, I get a long repeat list of "WARNING Desync detected. Attempting recovery." This problem does not occur with the drivers disabled. From testing, it appears this issue can in VERY rare cases just not happen with no ability to reproduce (restart alvr and steam vr with the same settings), and won't happen restarting the phone vr app until a couple seconds after starting. When it desyns, the headset will overestimate motion and wobble like crazy to an unusable degree. Here's a demonstration of the issue.

General Troubleshooting

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

Environment

Wayland

Hardware

https://linux-hardware.org/?probe=270423ce6c

CPU: AMD Ryzen 3 3100 4-Core Processor

GPU: Nvidia GeForce GTX 1660 Ti

GPU Driver Version: 570.133.07

Audio: Pipewire

Installation

ALVR Version: 20.13.0, 20.11.0

ALVR Settings File:
https://pastebin.com/jemPuav5

SteamVR Version: beta 2.10.2

Install Type:

• Packaged (exe, deb, rpm, etc)
• Portable (zip)
• ALVR dashboard from ALVR launcher

OS Name and Version (winver on Windows or grep PRETTY_NAME /etc/os-release on most Linux distributions): Fedora Linux 41 (KDE Plasma)

[KelvinGuy1]

So the solution is vaguely similar to the one proposed for slime trackers, wait for the headset to be connected before you start slime vr.

There isn't a super elegant solution to recreate this on a driver that has no UI. There is a hacky workaround however where you can just set poseIsValid based on if the headset pose is valid and connected.

Here's the code to check those two params:

bool IsHMDTracking()
{
    vr::TrackedDevicePose_t hmd_pose{};
    vr::VRServerDriverHost()->GetRawTrackedDevicePoses(0.0f, &hmd_pose, 1);

    // Check if the HMD pose is valid
    return hmd_pose.bPoseIsValid && hmd_pose.bDeviceIsConnected;
}

And you can put this in the 'vr::DriverPose_t GetPose()'

// Assumes vr::DriverPose_t pose;
pose.poseIsValid = IsHMDTracking() && whateverOtherParams;

I'll be phasing this code out for my own controller mounting stuff since it's more of a placeholder for my purposes, but virtual controller tracking with no UI like what valves controller driver demonstrates here will have to implement this code if they want to work with alvr.

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