[Linux] Intel Arc (DG2) VA-API encoders not detected due to lack of VAEntrypointEncSliceLP support

Description

This is a major complaint regarding ALVR on both a Linux Mint machine, and INTEL ARC GPU. I have tried ALVR last year, but I kept getting multiple issues with both ALVR and SteamVR.

On Linux, ALVR fails to detect any hardware encoders on Intel Arc GPUs (tested on DG2 / Arc A770). When launching ALVR with the Intel Media Driver (iHD), the logs report that H.264, HEVC, and AV1 profiles do not contain encoding entrypoints.

The root cause is that Intel DG2 / Alchemist hardware only exposes hardware encoding through VAEntrypointEncSliceLP (Low-Power / fixed-function hardware slices) rather than the legacy dual-mode VAEntrypointEncSlice. ALVR’s Linux VA-API detection logic currently checks strictly for VAEntrypointEncSlice, causing it to miss all valid hardware encoding profiles exposed by the driver.

General Troubleshooting

The only troubleshoot was switch to XE kernel driver, and installing the encoders, but ALVR told that there are no encoders whatsoever in XE, so I switched back to i915

Environment

X11 Cinnamon

Hardware

Note: for Linux, an upload to the hw-probe database is preferred: hw-probe -all -upload

PROBE URL: https://linux-hardware.org/?probe=8d0350e707

CPU: AMD RYZEN 7 5800X3D

GPU: INTEL ARC A770

GPU Driver Version: 0a:00.0 VGA compatible controller [0300]: Intel Corporation DG2 [Arc A770] [8086:56a0] (rev 08) Subsystem: Device [172f:4134] Kernel driver in use: i915 Kernel modules: i915, xe

Audio: N/A

Installation

ALVR Version: 20.14.1

ALVR Settings File: N/A

SteamVR Version: 2.17.9 (latest)

Install Type: Linux executable (x-executable)

OS Name and Version (winver on Windows or grep PRETTY_NAME /etc/os-release on most Linux distributions): LINUX MINT 22.3 (Ubuntu Noble 24.04)