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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
Download Patch File Download Diff File Expand all files Collapse all files
crates/punktfunk-host/src/encode.rs
+96 -44
View File
@@ -546,17 +546,40 @@ fn open_video_backend(
)
}
}
backend @ (WindowsBackend::Amf | WindowsBackend::Qsv) => {
// AMD AMF / Intel QSV via libavcodec (the Windows analogue of the Linux VAAPI path).
WindowsBackend::Amf => {
// AMD: the native AMF SDK encoder, unconditionally (design/native-amf-encoder.md
// Phase 3). The libavcodec AMF fallback and the `PUNKTFUNK_AMF_FFMPEG` hatch were
// removed once the native path was validated — two permanently-maintained AMF
// paths double the driver-matrix burden, and the one kept "for safety" is exactly
// the one with the wedge/latency pathology. No build feature: amfrt64.dll resolves
// at runtime like NVENC's DLL. A missing/ancient runtime fails HERE with the
// "install/update the AMD driver" message `AmfEncoder::open` raises (§6), rather
// than silently degrading — FFmpeg now serves QSV only.
amf::AmfEncoder::open(
codec,
format,
width,
height,
fps,
bitrate_bps,
bit_depth,
chroma,
)
.map(|e| Box::new(e) as Box<dyn Encoder>)
.map_err(|e| {
e.context(
"native AMF encode failed to open (update the AMD driver / amfrt64.dll \
runtime)",
)
})
}
WindowsBackend::Qsv => {
// Intel QSV via libavcodec (stays on FFmpeg — design/native-amf-encoder.md §2:
// async_depth=1 + low_power VDEnc is already near the hardware latency floor).
#[cfg(feature = "amf-qsv")]
{
let vendor = if matches!(backend, WindowsBackend::Amf) {
ffmpeg_win::WinVendor::Amf
} else {
ffmpeg_win::WinVendor::Qsv
};
ffmpeg_win::FfmpegWinEncoder::open(
vendor,
ffmpeg_win::WinVendor::Qsv,
codec,
format,
width,
@@ -570,11 +593,10 @@ fn open_video_backend(
}
#[cfg(not(feature = "amf-qsv"))]
{
let _ = backend;
anyhow::bail!(
"AMD/Intel (AMF/QSV) encode requested/detected but this host was built \
without it — rebuild with `--features amf-qsv` (needs ffmpeg-next + a \
FFMPEG_DIR with the AMF/QSV encoders at build time)"
"Intel (QSV) encode requested/detected but this host was built without \
it — rebuild with `--features amf-qsv` (needs ffmpeg-next + a FFMPEG_DIR \
with the QSV encoders at build time)"
)
}
}
@@ -785,14 +807,13 @@ pub fn can_encode_444(codec: Codec) -> bool {
false
}
}
WindowsBackend::Amf | WindowsBackend::Qsv => {
// AMD: native AMF never encodes 4:4:4 — VCN hardware limit, permanent, no probe
// needed (design/native-amf-encoder.md §3.5, Phase 3).
WindowsBackend::Amf => false,
WindowsBackend::Qsv => {
#[cfg(feature = "amf-qsv")]
{
let vendor = match windows_resolved_backend() {
WindowsBackend::Qsv => ffmpeg_win::WinVendor::Qsv,
_ => ffmpeg_win::WinVendor::Amf,
};
ffmpeg_win::probe_can_encode_444(vendor, codec)
ffmpeg_win::probe_can_encode_444(ffmpeg_win::WinVendor::Qsv, codec)
}
#[cfg(not(feature = "amf-qsv"))]
{
@@ -859,16 +880,18 @@ pub(crate) fn windows_resolved_backend() -> WindowsBackend {
}
}
/// True if the active Windows backend is the libavcodec AMF/QSV path (so the codec advertisement
/// consults a real GPU probe rather than the NVENC static superset). Always false when the
/// `amf-qsv` feature is off — there's then no ffmpeg backend to probe.
/// True if the active Windows backend's codec advertisement comes from a **real GPU probe**
/// ([`windows_codec_support`]) rather than the NVENC static superset. AMF always qualifies — the
/// native factory probe (`amf::probe_can_encode`) needs no build feature — while QSV still needs
/// the `amf-qsv` (libavcodec) build. Formerly `windows_backend_is_ffmpeg`, renamed when the
/// native AMF probe replaced the ffmpeg open-probe (design/native-amf-encoder.md §4, Phase 2).
#[cfg(target_os = "windows")]
pub fn windows_backend_is_ffmpeg() -> bool {
cfg!(feature = "amf-qsv")
&& matches!(
windows_resolved_backend(),
WindowsBackend::Amf | WindowsBackend::Qsv
)
pub fn windows_backend_is_probed() -> bool {
match windows_resolved_backend() {
WindowsBackend::Amf => true,
WindowsBackend::Qsv => cfg!(feature = "amf-qsv"),
WindowsBackend::Nvenc | WindowsBackend::Software => false,
}
}
/// Detect the encode-GPU vendor from the **selected render adapter** ([`crate::gpu::selected_gpu`]:
@@ -897,32 +920,55 @@ fn windows_gpu_vendor() -> Option<GpuVendor> {
})
}
/// Probe the active Windows AMF/QSV backend for its encodable codecs (opens a tiny encoder per
/// codec; cached **per (backend, selected GPU)** — a web-console preference change re-probes on the
/// newly selected adapter instead of serving the old GPU's answer for the process lifetime).
/// Mirrors [`vaapi_codec_support`]; called only when [`windows_backend_is_ffmpeg`] is true. AV1 is
/// narrow (AMD RDNA3+, Intel Arc/Xe2+), so it must be probed, not assumed.
#[cfg(all(target_os = "windows", feature = "amf-qsv"))]
/// Probe the active Windows AMF/QSV backend for its encodable codecs (cached **per (backend,
/// selected GPU)** — a web-console preference change re-probes on the newly selected adapter
/// instead of serving the old GPU's answer for the process lifetime). Mirrors
/// [`vaapi_codec_support`]; called only when [`windows_backend_is_probed`] is true. AV1 is narrow
/// (AMD RDNA3+, Intel Arc/Xe2+), so it must be probed, not assumed.
///
/// Mirrors the session dispatch (design/native-amf-encoder.md Phase 3): **AMD advertises from the
/// native AMF factory probe alone** (`amf::probe_can_encode`, on the selected adapter — the same
/// path the session opens, so the advertisement can never claim a codec the session can't emit);
/// **Intel/QSV uses the libavcodec probe** (all-`false` without the `amf-qsv` feature, matching a
/// build that cannot open QSV at all).
#[cfg(target_os = "windows")]
pub fn windows_codec_support() -> CodecSupport {
use std::collections::HashMap;
use std::sync::{Mutex, OnceLock};
static CACHE: OnceLock<Mutex<HashMap<String, CodecSupport>>> = OnceLock::new();
let vendor = match windows_resolved_backend() {
WindowsBackend::Qsv => ffmpeg_win::WinVendor::Qsv,
_ => ffmpeg_win::WinVendor::Amf,
};
let key = format!("{vendor:?}:{}", crate::gpu::selection_key());
let backend = windows_resolved_backend();
let key = format!("{backend:?}:{}", crate::gpu::selection_key());
let cache = CACHE.get_or_init(|| Mutex::new(HashMap::new()));
if let Some(c) = cache.lock().unwrap().get(&key) {
return *c;
}
let probe_one = |codec: Codec| -> bool {
match backend {
// AMD: the native factory probe is authoritative — it opens exactly the component the
// session will, so the advertisement matches what the encoder can emit by construction.
WindowsBackend::Amf => amf::probe_can_encode(codec),
WindowsBackend::Qsv => {
#[cfg(feature = "amf-qsv")]
{
ffmpeg_win::probe_can_encode(ffmpeg_win::WinVendor::Qsv, codec)
}
#[cfg(not(feature = "amf-qsv"))]
{
false
}
}
// Callers gate on `windows_backend_is_probed` — defensively answer "nothing probed"
// (the advertisement then falls back to the static superset).
WindowsBackend::Nvenc | WindowsBackend::Software => false,
}
};
let caps = CodecSupport {
h264: ffmpeg_win::probe_can_encode(vendor, Codec::H264),
h265: ffmpeg_win::probe_can_encode(vendor, Codec::H265),
av1: ffmpeg_win::probe_can_encode(vendor, Codec::Av1),
h264: probe_one(Codec::H264),
h265: probe_one(Codec::H265),
av1: probe_one(Codec::Av1),
};
tracing::info!(
backend = ?vendor,
?backend,
h264 = caps.h264,
h265 = caps.h265,
av1 = caps.av1,
@@ -933,8 +979,14 @@ pub fn windows_codec_support() -> CodecSupport {
caps
}
// Goal-1 stage 6: GPU/CPU encoders confined to `encode/windows/` (NVENC, AMF/QSV ffmpeg, software) and
// `encode/linux/` (NVENC/CUDA + VAAPI); `#[path]` keeps the `crate::encode::*` module names flat.
// Goal-1 stage 6: GPU/CPU encoders confined to `encode/windows/` (NVENC, native AMF, AMF/QSV
// ffmpeg, software) and `encode/linux/` (NVENC/CUDA + VAAPI); `#[path]` keeps the
// `crate::encode::*` module names flat.
// Native AMF (direct SDK, design/native-amf-encoder.md): compiled unconditionally on Windows —
// no build feature, the driver-installed amfrt64.dll resolves at runtime like NVENC's DLL.
#[cfg(target_os = "windows")]
#[path = "encode/windows/amf.rs"]
mod amf;
#[cfg(all(target_os = "windows", feature = "amf-qsv"))]
#[path = "encode/windows/ffmpeg_win.rs"]
mod ffmpeg_win;