enricobuehlerandClaude Fable 5 40030e90c8 fix(client): vendor-aware Windows decode order — D3D11VA first on Intel ...

Intel's Windows driver advertises Vulkan Video (Arc drivers since 2023), so
the capability gate alone no longer keeps Intel off FFmpeg-Vulkan — and that
combination is broken in the field (B580 report: strobing + 7.2 ms p50
decodes at 4K120) and on glass (Arc Pro iGPU: 29-33 ms p50 decodes at 4K60
where D3D11VA does 2.5 ms on the SAME GPU). Mirror the Linux vendor order on
Windows: NVIDIA/AMD keep Vulkan Video first, Intel/unknown take D3D11VA
first; vulkan stays reachable by explicit preference and as auto's fallback.

Also:
- Vulkan→D3D11VA mid-session demotion rung (the Windows analog of Linux's
  Vulkan→VAAPI rung) — a failing Vulkan backend lands on hardware, not on
  software, which cannot survive 4K120.
- The demotion streak now needs 1 s of age as well as 3 consecutive errors:
  a startup loss burst produced 3 errors in 20 ms and stranded the session
  on software decode (one-way) before the IDR requested on the first error
  could possibly arrive — live-hit on the Intel iGPU leg.
- Stale "Intel's Windows driver has no Vulkan Video" comments corrected,
  docs updated to the per-vendor order, vendor-order test extended with
  discrete/iGPU Arc cases.

Verified on an Arc Pro iGPU + RTX 3500 Ada laptop against a CachyOS/NVENC
host: auto now picks d3d11va on Intel (60 fps, 2.5-2.8 ms decode, e2e 26 ms
vs 50 ms before) and still picks vulkan on NVIDIA. 27/27 pf-client-core
tests, clippy clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

2026-07-19 14:04:32 +02:00

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docs

fix(client): vendor-aware Windows decode order — D3D11VA first on Intel

2026-07-19 14:04:32 +02:00