Describe the bug
Steam Link VR's video encoder is hard-capped at approximately 40 FPS on Linux, regardless of HMD refresh rate, render resolution, encode resolution, or any other setting. This causes 100-250ms of perceived stream latency, making VR not enjoyable. The same hardware works perfectly on Windows with no encode bottleneck.
The 40 FPS cap does NOT change when:
HMD refresh rate is changed (90Hz and 120Hz tested)
Render resolution is changed (150%, 100%, 20% tested)
Encode resolution is reduced (1536 or 2048 width)
10-bit encoding is disabled
Monitor refresh rate is changed (tested 60Hz, 120Hz, 240Hz)
GSP firmware is disabled (proprietary nvidia module with NVreg_EnableGpuFirmware=0)
KWin compositor is disabled
Process RT scheduling priorities are set (FIFO 90 for vrcompositor)
asyncSend and asyncStartEncode are enabled in driver_vrlink settings
The SteamVR Remote Detailed Debug overlay confirms: HMD target is 91 (or 120), LGPRX matches, but ENC stays locked at ~40 FPS. The dThrottle counter increments continuously, and the Enc bar dominates the latency graph.
To Reproduce
Connect Meta Quest 3 via Steam Link to a Linux PC with NVIDIA GPU
Launch SteamVR
Open SteamVR Remote Detailed Debug
Observe ENC FPS locked at ~40 regardless of HMD refresh rate or any other setting change
Expected behavior
Encoder FPS should match or exceed the HMD refresh rate (90/120 FPS), as it does on Windows with the same hardware.
vrcompositor log shows Async support disabled by user setting despite disableAsync being false in steamvr.vrsettings. This may contribute to the issue.
nvidia-smi reports 0% encoder utilization during streaming, which may indicate Vulkan Video Encode is not properly utilizing NVENC hardware, or that nvidia-smi doesn't track Vulkan Video Encode sessions.
The issue persists whether using nvidia-open (GSP enabled) or proprietary nvidia (GSP disabled).
Describe the bug
Steam Link VR's video encoder is hard-capped at approximately 40 FPS on Linux, regardless of HMD refresh rate, render resolution, encode resolution, or any other setting. This causes 100-250ms of perceived stream latency, making VR not enjoyable. The same hardware works perfectly on Windows with no encode bottleneck.
The 40 FPS cap does NOT change when:
The SteamVR Remote Detailed Debug overlay confirms: HMD target is 91 (or 120), LGPRX matches, but ENC stays locked at ~40 FPS. The
dThrottlecounter increments continuously, and the Enc bar dominates the latency graph.To Reproduce
Expected behavior
Encoder FPS should match or exceed the HMD refresh rate (90/120 FPS), as it does on Windows with the same hardware.
System Information:
Performance Data:
Screenshots
Additional context
Async support disabled by user settingdespitedisableAsyncbeingfalseinsteamvr.vrsettings. This may contribute to the issue.nvidia-smireports 0% encoder utilization during streaming, which may indicate Vulkan Video Encode is not properly utilizing NVENC hardware, or thatnvidia-smidoesn't track Vulkan Video Encode sessions.