Troubleshooting NVIDIA NVENC Lossless Mode

Agent-Side Troubleshooting

Lossless mode does not activate, resulting in the sessions not utilizing lossless encoding even when the required configuration and conditions are met.

Possible Causes and Solutions:

1. Registry Key Not Set or Incorrect Spelling, or Incorrect Location

   • Verification: Check the registry key as described in the Verification section
   • Solution: Set EncoderAlwaysLossless=1 as shown in the Configuration section

2. Incompatible GPU Hardware

   • Verification: Check if your GPU is from Pascal family or newer
   • Solution: Verify GPU model against NVIDIA’s Video Encode & Decode Support Matrix and if GPU doesn’t support HEVC 4:4:4, the system will automatically fall back to BlastCodec

3. Outdated Agent Display Driver

   • Verification: Check driver version and NVIDIA license
     • Windows: Run nvidia-smi or check Device Manager
     • Linux: Run nvidia-smi or cat /proc/driver/nvidia/version
   • Solution: Update to driver version to latest GRID driver supported in the hypervisor environment and provide NVIDIA licensing.

4. Resource Contention

   • Symptoms: Encoder fails under heavy load or with multiple sessions
   • Verification: Check blast worker logs for encoder initialization failures
   • Solution:
     • Monitor GPU utilization using nvidia-smi
     • Check for other applications using NVENC
     • Increase the vGPU profile to increase GPU resources allocated to the VM

Client-Side Troubleshooting

NVENC HEVC Lossless mode is not functioning on the client, preventing users from experiencing high-performance NVENC lossless display even when it is enabled and supported on the server side.

Possible Causes and Solutions:

1. HEVC-4:4:4 Decoding Not Enabled on the client side

   • Verification: Check client preferences.
   • Solution: Enable both “Allow HEVC Decoding” and “Allow High Definition Color” settings. See Enabling NVIDIA NVENC Lossless Mode

2. Client GPU does not support HEVC 4:4:4 (High-Definition Color)

   • Verification: Check codec probing log at %TEMP%\omnissa-[user]-####\horizon-mksprobe-[PID].log for a logline mentioning: “Hardware HEVC 4:4:4 8-bit: Available up to 7680x4320, supports: I601 H709 F709”
   • Solution:
     • Verify GPU supports HEVC 4:4:4 decoding
     • For NVIDIA: Ensure GPU is Turing family or newer
     • For Intel: Check Intel’s GPU support matrix

3. Resource or Software Constraints

   • Known Issue: Some decoder configurations fail with specific resolution/frame rate combinations
   • Example: Intel Iris GPU with Linux client may not enable lossless (Reference: VCART-10097, DPM-17695)
   • Verification: Check logs on horizon-protocol-###.log for decoder errors
   • Solution:
     • Try different resolution settings
     • Update client GPU drivers
     • Check for OS-specific graphics driver issues

Note: For both agent and client debugging, it is recommended to run nvidia-smi to ensure that the driver is loaded. This applies to both Windows and Linux agents. Additionally, on Windows, you can check the display adapter in Device Manager to ensure there are no errors.