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feat(linux): zero-copy 4:4:4 — the EGL worker converts to planar YUV444 on the GPU

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A 4:4:4 session no longer falls to the CPU path (SHM capture + swscale
RGB→YUV444P + re-upload — the fps-ceiling triple tax). The zero-copy worker
grows a Yuv444Blit: three full-res R8 GL passes (the proven BT.709
coefficients; studio or full range per PUNKTFUNK_444_FULLRANGE, read by both
processes so pixels and VUI flip together) into ONE stacked 3-plane pitched
CUDA allocation — which keeps the worker↔host wire and IPC single-plane. The
encoder copies the planes into ffmpeg's yuv444p CUDA surface and hevc_nvenc
emits Range-Extensions 4:4:4 natively.

ImportKind::Tiled444 is APPENDED to the worker protocol (a worker outliving a
replaced host binary must keep the old tags stable; an old worker just errors
the import, which the fail machinery already handles). A 4:4:4 session on a
LINEAR/gamescope capture — no convert wired there — fails with a clear message
instead of letting hevc_nvenc silently subsample. caps().chroma_444 now keys
off the session (it missed the GPU path when keyed off the swscale's
existence).

Live-verified on the CachyOS VM (RTX 5070 Ti): per-frame "imported to CUDA
yuv444=true", stream Rext/yuv444p/bt709 in both tv and pc range, no CPU-path
warning.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-07-10 18:08:41 +02:00
parent 5f687a7083
commit 0dacb37088
13 changed files with 532 additions and 73 deletions
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crates/punktfunk-host/src/capture.rs
+13 -5
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@@ -37,12 +37,19 @@ pub enum PixelFormat {
/// `P010` (DXGI `P010`): 10-bit BT.2020 PQ limited-range YUV 4:2:0. HDR analogue of [`Nv12`]:
/// video-processor output for HEVC Main10 / HDR10, handed to NVENC as `YUV420_10BIT`.
P010,
/// Planar 8-bit YUV **4:4:4** (BT.709; range per `PUNKTFUNK_444_FULLRANGE`). Produced by the
/// Linux zero-copy worker's GPU convert for a 4:4:4 session ([`FramePayload::Cuda`] with
/// `DeviceBuffer::yuv444` — three full-res planes stacked in one allocation); NVENC encodes
/// it natively under the Range-Extensions profile. Never a CPU payload.
Yuv444,
}
impl PixelFormat {
pub fn bytes_per_pixel(self) -> usize {
match self {
PixelFormat::Rgb | PixelFormat::Bgr => 3,
// Three full-res 1-byte planes (GPU-resident only; no CPU payload carries this).
PixelFormat::Yuv444 => 3,
_ => 4,
}
}
@@ -381,11 +388,12 @@ pub fn capture_virtual_output(
_capture: crate::session_plan::CaptureBackend,
) -> Result<Box<dyn Capturer>> {
// The Linux host stays 8-bit (HDR is blocked upstream) and the portal negotiates its own pixel
// format, so only `want.gpu` is honored here: it gates GPU zero-copy capture (the capture backend
// is always the portal — the `CaptureBackend` arg is a Windows-only dispatch). `gpu = false`
// (a 4:4:4 NVENC session) forces the CPU mmap path so the encoder gets CPU-resident RGB to swscale
// into YUV444P — otherwise it would receive CUDA frames and bail.
linux::PortalCapturer::from_virtual_output(vout, want.gpu)
// format, so `want.gpu` gates GPU zero-copy capture (the capture backend is always the portal —
// the `CaptureBackend` arg is a Windows-only dispatch) and `want.chroma_444` selects the
// worker's planar-YUV444 GPU convert for tiled dmabufs (the 4:4:4 zero-copy path). `gpu =
// false` (4:4:4 without zero-copy) forces the CPU mmap path so the encoder gets CPU-resident
// RGB to swscale into YUV444P.
linux::PortalCapturer::from_virtual_output(vout, want.gpu, want.chroma_444)
.map(|c| Box::new(c) as Box<dyn Capturer>)
}