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feat(host): native AMF SDK encoder for Windows AMD — drop libavcodec

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Direct-SDK AMF encoder (encode/windows/amf.rs), the AMD analogue of the
direct-NVENC path, replacing the libavcodec *_amf dispatch. C-vtable FFI
pinned to AMF headers v1.4.36, runtime-loaded from the driver's amfrt64.dll
(no build feature, no new dependency) exactly as NVENC loads its DLL.

- AVC/HEVC (SDR NV12 + 10-bit HDR P010) and AV1 (RDNA3+, probed); a bounded
  poll retires the libavcodec ~2-frame output hold; native in-place reset().
- Intra-refresh wave (PUNKTFUNK_INTRA_REFRESH), in-band HDR mastering/CLL
  metadata (*InHDRMetadata -> HEVC SEI / AV1 OBU), and a native codec probe
  feeding the GameStream advertisement (windows_backend_is_ffmpeg ->
  windows_backend_is_probed).
- AMD dispatch / advertisement / 4:4:4 are native-only; the libavcodec AMF
  fallback and the PUNKTFUNK_AMF_FFMPEG hatch are removed. FFmpeg serves QSV
  only (its AMF path retained solely as the latency A/B comparator).
- Overload back-pressure: submit bounds in-flight surfaces below the input
  ring, draining finished AUs (buffered for poll, FIFO-preserved) to free a
  slot and retry on AMF_INPUT_FULL instead of tearing the encoder down and
  forcing an IDR; this also closes a latent ring-overwrite corruption seen
  under load on-glass.

Validated on the lab Ryzen iGPU (AMF runtime 1.4.37): HEVC/AVC across a
native reset, HEVC Main10 mastering+CLL SEIs byte-verified, intra-refresh
accepted, a backpressure burst FIFO-clean, and end-to-end via the macOS
client. Measured §5.2 latency A/B: native encode_us p50 ~5 ms (0.31 frame
periods) vs libavcodec ~17 ms (1.01). 4:4:4 stays unsupported (VCN hardware
limit). Live-gated tests skip cleanly on non-AMD boxes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-07-06 17:32:30 +02:00
parent 19388f3412
commit 6f47abab8c
4 changed files with 2741 additions and 53 deletions
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crates/punktfunk-host/src/encode/windows/ffmpeg_win.rs
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//! AMD **AMF** and Intel **QSV** hardware encode on Windows via `ffmpeg-next` — the Windows
//! analogue of the Linux [`super::vaapi`] backend (one libavcodec backend per vendor, selected by
//! encoder name: `*_amf` / `*_qsv`). This is the sibling of the direct-SDK [`super::nvenc`] path
//! behind the shared [`Encoder`] trait, selected in [`super::open_video`] (NVIDIA → NVENC,
//! AMD → AMF, Intel → QSV).
//! Intel **QSV** (and, retained-but-no-longer-dispatched, AMD **AMF**) hardware encode on Windows
//! via `ffmpeg-next` — the Windows analogue of the Linux [`super::vaapi`] backend (one libavcodec
//! backend per vendor, selected by encoder name: `*_qsv` / `*_amf`). Sibling of the direct-SDK
//! [`super::nvenc`] path behind the shared [`Encoder`] trait.
//!
//! **Dispatch (design/native-amf-encoder.md Phase 3):** [`super::open_video`] routes AMD to the
//! direct-SDK [`super::amf`] encoder, not this module — the libavcodec AMF wrapper's ~2-frame
//! output hold and its silent-wedge failure mode are exactly why the native path exists. So in
//! production this file serves **QSV only**. The `WinVendor::Amf` machinery is kept (not deleted)
//! because it is the comparator in the native-vs-libavcodec latency A/B (`amf::tests::
//! amf_latency_ab_bench`), and excising it would churn the shared, Intel-unvalidated QSV code for
//! no production benefit. Treat every `WinVendor::Amf` arm below as benchmark-only.
//!
//! The capturer hands a `FramePayload::D3d11` texture (NV12/P010 from the D3D11 video processor, or
//! BGRA/Rgb10a2 as a fallback) on the capturer's own `ID3D11Device`. Two input paths, chosen lazily