NVIDIA 940MX: No VA-API Profile Found

by Alex Johnson 38 views

If you're diving into the world of video acceleration on Linux, especially with a dual-graphics setup involving an Intel iGPU and an NVIDIA GeForce 940MX, you might run into a puzzling issue: the absence of VA-API profiles. This article aims to shed light on this situation, explore the possible reasons, and guide you through troubleshooting steps. We'll be focusing on the NVIDIA 940MX VA-API profile problem, ensuring you have the knowledge to tackle it head-on.

Understanding VA-API and Its Importance

First off, let's quickly recap what VA-API (Video Acceleration API) is all about. In simple terms, it's a Linux API that allows applications to utilize hardware-accelerated video decoding and encoding. This is a huge deal for performance. Instead of relying solely on your CPU, which can quickly become a bottleneck, VA-API offloads these demanding tasks to specialized hardware components within your graphics card. This means smoother video playback, faster video editing, and more efficient video conferencing, all while consuming less power. The NVIDIA 940MX VA-API driver is the bridge that enables this acceleration for NVIDIA cards.

When we talk about VA-API profiles, we're referring to specific sets of features and capabilities that a video codec (like H.264, HEVC, VP9, etc.) supports. For instance, H.264 has various profiles, such as High, Main, and Baseline, each with different levels of compression efficiency, quality, and complexity. Hardware decoders and encoders are designed to support a subset of these profiles. When an application needs to encode or decode a video, it checks which profiles the VA-API driver supports and then selects one that matches the video's requirements. If the driver doesn't report any supported profiles, the application falls back to software decoding/encoding, which, as we've established, isn't ideal.

The Case of the Missing NVIDIA 940MX VA-API Profiles

The core of the problem, as highlighted in the provided logs, is that even when the NVIDIA driver and VA-API seem to load correctly, the output from vainfo doesn't list any supported profiles. This is perplexing because the NVIDIA 940MX VA-API hardware should support several common profiles, particularly for H.264, as indicated by NVIDIA's own documentation. Let's break down the provided information to see what's happening.

We see that the nvidia_drv.so Xorg driver is loaded, and the nvidia_drv_video.so is found in the dri directory. The lspci command confirms the presence of the NVIDIA Corporation GM107 [GeForce 940MX]. The nvidia-smi output also shows the GPU is recognized and operating, albeit at a low power state, which is expected when not under heavy load.

Crucially, the vainfo command, when run with LIBVA_DRIVER_NAME=nvidia and NVD_BACKEND=egl (or direct), does initialize the NVIDIA VA-API driver. The logs show messages like Initialising NVIDIA VA-API Driver, Got DRM FD: 1 3, and Selecting EGL backend or Selecting Direct backend. This indicates that the VA-API driver is attempting to interface with the hardware. However, the subsequent output shows "Supported profile and entrypoints" followed by nothing, and then the driver terminates cleanly.

Investigating the Logs: EGL vs. Direct Backend

It's interesting to note the two different outputs from vainfo based on the NVD_BACKEND environment variable. When NVD_BACKEND=egl is used, the log indicates Selecting EGL backend and messages related to EGL devices. When NVD_BACKEND=egl is not set (or if it defaults to 'direct' in this context, as seen in the second vainfo run), it logs Selecting Direct backend and mentions the NVIDIA kernel driver version. Both scenarios lead to the same outcome: no listed profiles.

EGL Backend Analysis:

The EGL backend is typically used when you're running applications that leverage EGL for rendering, often in conjunction with Wayland or certain OpenGL applications. The logs show that the driver correctly identifies the DRM device and EGL devices. It even finds a GPU index based on the DRM device. However, after this, it seems to fail in enumerating or reporting the supported profiles.

Direct Backend Analysis:

The direct backend is a more traditional approach, interacting more directly with the kernel driver. The logs here show the NVIDIA kernel driver version (535.274.02) being successfully identified. This suggests a good level of communication between the VA-API driver and the kernel module. Yet, again, the vainfo output is empty regarding profiles.

Possible Causes for Missing VA-API Profiles

Given that the driver initializes but doesn't report profiles, we can narrow down the potential causes:

  1. Driver Bug or Incompatibility: This is a common culprit. It's possible there's a bug within the specific version of the nvidia-vaapi-driver or the NVIDIA proprietary driver that prevents it from correctly enumerating the supported profiles on this particular GPU model or chipset combination (Intel HD 620 iGPU + NVIDIA 940MX).
  2. Kernel Module Issues: While nvidia-smi works, there might be subtle issues with how the NVIDIA kernel module (nvidia.ko) interacts with the VA-API driver, especially concerning DRM device handling.
  3. Configuration Problems: Although the logs indicate successful loading, there might be an underlying configuration issue that prevents the driver from accessing or correctly interpreting the hardware capabilities. This could be related to how DRM devices are exposed or permissions.
  4. Hardware Limitations (Less Likely): While NVIDIA's documentation suggests support for H.264 profiles, it's remotely possible that the specific implementation on the 940MX has quirks that aren't fully exposed or supported by the driver in this Linux environment. However, given it's a common mobile GPU, this is less probable than a software issue.
  5. User-space Library Conflicts: Less likely, but worth considering, are conflicts between different versions of libva or related libraries that the nvidia-vaapi-driver depends on.

Troubleshooting Steps

Let's systematically try to resolve this NVIDIA 940MX VA-API profile issue:

  1. Update Everything: Ensure your system is fully updated. This includes the kernel, NVIDIA proprietary drivers, libva, libva-utils, and the nvidia-vaapi-driver package itself. Sometimes, these issues are resolved in newer releases.
    # For Debian/Ubuntu based systems
sudo apt update && sudo apt upgrade
# For Fedora based systems
sudo dnf upgrade
# Check for specific driver package updates
  2. Try Different Driver Versions: If you're using the latest NVIDIA driver, try rolling back to a slightly older, stable version. Conversely, if you're on an older driver, try updating. The same applies to the nvidia-vaapi-driver if it's a separate package.
  3. Verify DRM Device Access: Ensure your user has the necessary permissions to access the DRM device (/dev/dri/renderD128). Usually, users are part of the video or render group. Check with groups $(whoami) and add yourself if necessary: sudo usermod -aG video $(whoami) (log out and back in after).
  4. Explicitly Set LIBVA_DRIVERS_PATH (Advanced): Sometimes, libva might not find the driver correctly. You can try explicitly telling it where to look. Find the nvidia_drv_video.so path (e.g., /usr/lib/x86_64-linux-gnu/dri/) and set the environment variable:
    export LIBVA_DRIVERS_PATH=/usr/lib/x86_64-linux-gnu/dri/
vainfo
  5. Check Xorg Configuration: While less likely to affect VA-API directly, ensure your Xorg configuration isn't inadvertently causing issues. Usually, for dual-graphics setups, nvidia-xconfig might create a configuration that needs review, although modern systems often handle this automatically.
  6. Test with a Different Application: Try using a video player known to support VA-API, like mpv or vlc. Configure them to specifically use the VA-API backend and see if they report errors or fall back to software decoding. For mpv, you might try:
    mpv --hwdec=vaapi your_video_file.mp4
    Check the terminal output for mpv for any VA-API related errors.
  7. Consult NVIDIA Developer Forums: The official NVIDIA developer forums are an excellent resource. Post your vainfo output, system details, and driver versions. Other users or NVIDIA engineers might have encountered and solved similar issues. You can find them here: NVIDIA Developer Forums.
  8. Check VA-API Support Matrix: As you noted, the NVIDIA Video Encode and Decode Support Matrix is the definitive source for hardware capabilities. Double-check that the profiles listed there are indeed expected for your specific 940MX variant and driver generation. Sometimes, mobile versions have slightly different support.

Conclusion

The absence of VA-API profiles on a system with an NVIDIA 940MX, despite the driver initializing, points towards a potential software or configuration glitch rather than a fundamental hardware limitation. By systematically working through the troubleshooting steps, updating your system, verifying permissions, and seeking community support, you increase your chances of enabling hardware video acceleration. Remember, smooth video playback and efficient encoding are achievable, and understanding the NVIDIA 940MX VA-API nuances is key to unlocking that potential.

For further assistance and to connect with experts, the NVIDIA Developer Forums are a valuable resource. Additionally, for broader Linux graphics discussions, the LinuxQuestions.org Hardware Section can also provide insights.