Stage 1.5: on Intel/AMD clients libavcodec's VAAPI hwaccel decodes on
the GPU; frames map to DRM-PRIME dmabufs (av_hwframe_map, zero copy)
and reach GTK as GdkDmabufTexture (BT.709 limited CICP color state —
GDK's dmabuf default is BT.601). Inside GtkGraphicsOffload that is the
decoder-to-subsurface path, direct-scanout eligible when fullscreen.
Fallback ladder, live-verified on the NVIDIA dev box: no VAAPI device
-> software decode at session start (logged reason); a mid-session
VAAPI error (e.g. broken nvidia-vaapi-driver) demotes to software and
the host's IDR/RFI recovery resynchronizes; a rejected dmabuf import
logs and the stream continues. PUNKTFUNK_DECODER=software|vaapi
overrides; the first-frame log now names the active path.
The hwaccel path is raw ffmpeg-sys FFI (ffmpeg-next wraps none of it):
hw device ctx + get_format pinned to AV_PIX_FMT_VAAPI (NONE on
mismatch so cpu-fallback never silently engages inside libavcodec),
thread_count=1, LOW_DELAY. Surface lifetime rides DrmFrameGuard into
the texture's release func — GDK runs it on both success and failure.
Needs an Intel/AMD client box (Steam Deck/Bazzite) to live-verify the
hardware path; the software path is unchanged and revalidated.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehler
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