Design + decision record for replacing the libavcodec *_amf path with a
direct AMF SDK encoder (encode/windows/amf.rs, the AMD analogue of the direct
NVENC path). Motivation is measured, not speculative: the libavcodec wrapper
structurally holds ~2 frames (36 ms p50 at 720p60 on VCN, un-tunable), driver
wedges surface as forever-EAGAIN instead of typed AMF_RESULTs, and
intra-refresh / in-band HDR SEI are inexpressible through it. Covers the C
vtable FFI strategy (amfrt64.dll runtime-load, FFmpeg amfenc.c and OBS
texture-amf.cpp as references), bounded-poll retrieval, the property table,
watchdog/reset interplay, exact dispatch seams, a lab-iGPU validation plan
with today's zero-copy baselines, and three phases ending with the ffmpeg-AMF
arm deleted (FFmpeg stays QSV-only).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
