QuestLHSync

Lighthouse trackers, controllers and base stations aligned to a Quest's or a Steam Frame's own tracking, with nothing mounted on the headset. The headset's tracking cameras see the laser flashes of SteamVR base stations, and QuestLHSync uses them to keep the lighthouse space lined up with the headset's while you play. No SpaceCalibrator, no tracker strapped to your head.

It has two parts: a headset part, which serves what the cameras see on your local network (a Magisk module on a Quest, a user service and a small SteamVR driver on a Steam Frame), and a SteamVR driver for the PC, which solves the alignment, applies it to every lighthouse device and adds a page to the SteamVR dashboard.

Steam Frame support is by @NotZoeyDev.

• A Quest Pro, Quest 3 or Quest 3S, rooted with Magisk.
• Or a Steam Frame. No root, no developer password: everything installs as your user.
• SteamVR base stations, 1.0 or 2.0.
• Windows with SteamVR, with the headset streamed by anything: Steam Link, Link, Air Link, Virtual Desktop, ALVR, CreoleCast...
• The PC and the headset on the same local network.
• At least one lighthouse device switched on (a tracker or an Index controller). SteamVR only shows base stations while one is on.

Each device has its own file in Releases.

1. Headset:

   • Quest: install QuestLHSync-quest-module-<version>.zip in the Magisk app (Modules > Install from storage) and reboot. Or over adb:

     adb push QuestLHSync-quest-module-<version>.zip /sdcard/Download/
     adb shell su -c "magisk --install-module /sdcard/Download/QuestLHSync-quest-module-<version>.zip"
     adb reboot
     

   • Steam Frame: in Desktop Mode, open QuestLHSync-frame-installer.flatpak in Discover, then start QuestLHSync Installer and click Install. Or copy QuestLHSync-frame-module-<version>.tar.gz to the Frame and, in a terminal on it or over ssh:

     tar xzf QuestLHSync-frame-module-<version>.tar.gz
     QuestLHSync-frame/install.sh
     

     Either way, SteamVR on the headset restarts once to load its driver.

2. PC: run QuestLHSync-steamvr-installer.exe. It downloads the latest release, installs the driver to %LOCALAPPDATA%\QuestLHSync\questlhsync, registers it with SteamVR (in place of a copy you registered by hand) and offers an update whenever a newer release is out. It closes SteamVR if it's running.

   Or by hand: extract the questlhsync folder from QuestLHSync-steamvr-<version>.zip somewhere permanent and, with SteamVR closed, register it:

   "C:\Program Files (x86)\Steam\steamapps\common\SteamVR\bin\win64\vrpathreg.exe" adddriver "C:\path\to\questlhsync"
   

3. Turn off SpaceCalibrator, OpenVR-SpaceSync or anything else that moves lighthouse devices. Two tools correcting the same devices fight each other.

Start SteamVR as usual. QuestLHSync finds the headset by itself. Its page is in the SteamVR dashboard, with a copy on the desktop.

The first time, look around so the cameras catch both base stations (the Frame uses only its two upper cameras: the lower pair looks at the floor, not at the base stations). It locks within about half a minute, and after that starts from the saved alignment. Wear a tracker or hold a controller meanwhile: when two base stations could be either way round, the devices you wear or hold decide.

With three base stations, glance at the third one too. QuestLHSync's reference frame keeps whatever tilt SteamVR's lighthouse space had when it was first seen, and with two base stations in view a tilt of 1.5° puts trackers on the floor 15 cm to the side. Once the cameras have seen three base stations well enough to tell, QuestLHSync levels the reference frame with the headset's gravity and keeps the level in stations.json. With two, the lighthouse controllers' and trackers' accelerometers level it as they move about.

• Pause corrections holds lighthouse devices where they are.
• Record session saves what the driver receives to a file, for bug reports.
• Force recalibrate drops everything learned about the alignment and starts over, for when it sits stuck on a wrong fit. It clears the sightings, the fit, the headset's saved alignment and pose timing, and an automatic reference frame (stations.json: pinned again from SteamVR's base stations, its level found again). Lighthouse devices go back to SteamVR's own places until the cameras have found the base stations again. A reference frame you measured yourself stays.

What a headset's cameras have seen is kept per headset, in %LOCALAPPDATA%\QuestLHSync\headsets\<model>-<id>\state.json (the id is a hash of its serial number), so switching between headsets doesn't seed one with the other's alignment or pose timing. The state.json of earlier versions moves to the first headset that connects. stations.json, the reference frame of your base stations, is shared by all headsets.

Optional, in steamvr.vrsettings under "driver_questlhsync":

With a wired headset (SteamVR's headset is a lighthouse one, or tracked by a driver that isn't a streamer's: Index, Vive, Windows Mixed Reality, ...), QuestLHSync switches itself off: no corrections, no levelling, no base station averaging, and the dashboard closes. anyHmd keeps it on for a headset it wouldn't otherwise accept (never a lighthouse one).

• "Looking for the headset": the headset must be awake and on the same network. If your router drops broadcasts, set host.
• "No camera frames": the cameras only run while the headset tracks. Put it on. If it stays there, check %LOCALAPPDATA%\QuestLHSync\questlhsync.log: a no camera buffers found line means the headset part doesn't know this headset or OS build yet. Please open an issue with that line. On the Frame, a "questlhsync_frame SteamVR driver isn't running" line means SteamVR on the headset hasn't restarted since the install: systemctl --user restart steamvr.service.
• "Waiting for base stations": switch on a tracker or controller.
• "Finding the base stations" for a long time: face each base station for a few seconds.

The PC side writes only to %LOCALAPPDATA%\QuestLHSync and only talks to the headset. The headset part answers anyone on the local network without authentication. It sends bright-spot positions (never images), the camera calibration, and the headset's serial number, model and firmware. Use it on a network you trust. It only reads the cameras while a PC is connected, and patches nothing on disk. On the Frame, lhsyncd logs to the user journal (journalctl --user -u questlhsync).

• Quest: remove the module in the Magisk app and reboot.
• Steam Frame: click Uninstall in QuestLHSync Installer, or run QuestLHSync-frame/uninstall.sh on the headset.
• PC: with SteamVR closed, click Uninstall in the installer, or run vrpathreg removedriver "C:\path\to\questlhsync" and delete %LOCALAPPDATA%\QuestLHSync.

Visual Studio 2022 with C++, the Android NDK, Zig and Python 3:

build.bat                        SteamVR driver + dashboard app (SteamVR closed) + out\QuestLHSync-Installer.exe
build.bat installer              only the installer
python magisk\build_module.py    Quest module (Magisk), into out\
python frame\build.py            Steam Frame package, into out\
python release.py                the release files, into out\release-<version>\
python install.py                register driver\questlhsync with SteamVR
python install.py headset        install the module over adb, no reboot

Zig cross-compiles the Steam Frame package (zig on PATH, or ZIG set to it). On the Frame itself or any arm64 Linux, frame/build.py uses cc and c++ instead.

The Steam Frame's installer app is a Flatpak, built on Linux for the machine's own architecture (so on the Frame, or any arm64 Linux) with python3 frame/installer/build.py, into out/QuestLHSync-frame-installer-<version>.flatpak. It needs flatpak-builder and the GNOME SDK: flatpak install --user flathub org.flatpak.Builder org.gnome.Sdk//50. release.py adds it to the release files as QuestLHSync-frame-installer.flatpak when it's in out/.

lhsyncd's core (src/headset/lhsyncd.c) is shared by both headsets; each adds its own side behind src/headset/headset.h (magisk/src/quest.c, frame/src/frame.c).

MIT, see LICENSE. Third-party code is listed in THIRD_PARTY_NOTICES.md.

QuestLHSync is not affiliated with Meta or Valve. Meta Quest is a trademark of Meta Platforms, Inc.; Steam Frame and SteamVR are trademarks of Valve Corporation. Rooting a headset and running code inside its system services is at your own risk.