enricobuehler
16a00563a8
Scaffolding for dmabuf zero-copy (plan §9), opt-in via LUMEN_ZEROCOPY:
- src/zerocopy/{cuda,egl}.rs: hand-rolled CUDA Driver-API FFI (no Rust crate
exposes the EGL-interop calls / CUeglFrame) with a shared process-wide
CUcontext + pitched device buffers; an EGL importer (GBM platform on the
NVIDIA render node) that turns a dmabuf into an EGLImage, registers it with
CUDA, and copies it device-to-device into an owned buffer. `zerocopy-probe`
subcommand validates the FFI/linking/GPU access — confirmed on the box
(driver 595, EGL_EXT_image_dma_buf_import + modifiers).
- CapturedFrame gains a FramePayload enum (Cpu(Vec<u8>) | Cuda(DeviceBuffer));
the encoder branches: CPU keeps the expand+upload path, CUDA wraps the device
buffer in an AV_PIX_FMT_CUDA frame fed straight to hevc_nvenc (sharing our
CUcontext via a hand-declared AVCUDADeviceContext, since ffmpeg-sys doesn't
bind hwcontext_cuda.h). open_video/the encoder take a `cuda` flag derived from
the first frame's payload.
The capture-side dmabuf negotiation (which produces the Cuda frames) is the
next step; the CPU path is unchanged and remains the default + fallback. Builds
clean, clippy clean, tests pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
359 lines
14 KiB
Rust
359 lines
14 KiB
Rust
//! NVENC encoder via `ffmpeg-next` (binds the system FFmpeg 7.x / libavcodec 61).
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//!
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//! Input is a packed RGB/BGR CPU frame; `*_nvenc` accepts `rgb0`/`bgr0`/`rgba`/`bgra`
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//! directly and does the RGB→YUV conversion on the GPU, so the host stays off the
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//! colour-conversion path. The portal commonly negotiates packed 24-bit `RGB`, which NVENC
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//! does *not* accept — we expand it to `rgb0` (one padding byte/pixel, no colour math).
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//! The encoder is opened *without* a global header so VPS/SPS/PPS are emitted in-band on
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//! every IDR — the output is both a playable raw Annex-B stream and self-contained AUs.
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use super::{Codec, EncodedFrame, Encoder};
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use crate::capture::{CapturedFrame, FramePayload, PixelFormat};
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use anyhow::{anyhow, bail, Context, Result};
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use ffmpeg::format::Pixel;
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use ffmpeg::util::frame::Video as VideoFrame;
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use ffmpeg::{codec, encoder, Dictionary, Packet, Rational};
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use ffmpeg_next as ffmpeg;
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use std::os::raw::c_int;
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use ffmpeg::ffi; // = ffmpeg_sys_next
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/// `AVCUDADeviceContext` (libavutil/hwcontext_cuda.h) — not in the ffmpeg-sys bindings (the
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/// crate doesn't allowlist that header), so mirror its stable 3-pointer layout. We set the
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/// first field to *our* `CUcontext` so NVENC shares the context the EGL importer maps into.
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#[repr(C)]
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struct AVCUDADeviceContext {
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cuda_ctx: *mut std::ffi::c_void, // CUcontext
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stream: *mut std::ffi::c_void, // CUstream (null = default)
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internal: *mut std::ffi::c_void, // filled by ctx_init
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}
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/// CUDA hardware-frame contexts that wrap our shared `CUcontext`, so `hevc_nvenc` reads the
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/// imported device buffer directly. Owns two `AVBufferRef`s, unref'd on drop.
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struct CudaHw {
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device_ref: *mut ffi::AVBufferRef,
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frames_ref: *mut ffi::AVBufferRef,
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}
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impl CudaHw {
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/// Build a CUDA hwdevice wrapping `cu_ctx` and a frames pool (`sw_format` = `pixel`).
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unsafe fn new(cu_ctx: *mut std::ffi::c_void, sw_format: Pixel, w: u32, h: u32) -> Result<Self> {
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let mut device_ref = ffi::av_hwdevice_ctx_alloc(ffi::AVHWDeviceType::AV_HWDEVICE_TYPE_CUDA);
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if device_ref.is_null() {
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bail!("av_hwdevice_ctx_alloc(CUDA) failed");
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}
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let dev_ctx = (*device_ref).data as *mut ffi::AVHWDeviceContext;
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let cu = (*dev_ctx).hwctx as *mut AVCUDADeviceContext;
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(*cu).cuda_ctx = cu_ctx; // share the importer's context
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let r = ffi::av_hwdevice_ctx_init(device_ref);
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if r < 0 {
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ffi::av_buffer_unref(&mut device_ref);
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bail!("av_hwdevice_ctx_init failed ({r})");
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}
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let mut frames_ref = ffi::av_hwframe_ctx_alloc(device_ref);
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if frames_ref.is_null() {
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ffi::av_buffer_unref(&mut device_ref);
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bail!("av_hwframe_ctx_alloc failed");
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}
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let fc = (*frames_ref).data as *mut ffi::AVHWFramesContext;
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(*fc).format = ffi::AVPixelFormat::AV_PIX_FMT_CUDA;
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(*fc).sw_format = pixel_to_av(sw_format);
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(*fc).width = w as c_int;
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(*fc).height = h as c_int;
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(*fc).initial_pool_size = 0; // we supply the device pointers
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let r = ffi::av_hwframe_ctx_init(frames_ref);
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if r < 0 {
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ffi::av_buffer_unref(&mut frames_ref);
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ffi::av_buffer_unref(&mut device_ref);
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bail!("av_hwframe_ctx_init failed ({r})");
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}
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Ok(CudaHw {
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device_ref,
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frames_ref,
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})
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}
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}
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impl Drop for CudaHw {
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fn drop(&mut self) {
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unsafe {
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ffi::av_buffer_unref(&mut self.frames_ref);
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ffi::av_buffer_unref(&mut self.device_ref);
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}
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}
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}
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/// `ffmpeg::format::Pixel` → raw `AVPixelFormat`.
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fn pixel_to_av(p: Pixel) -> ffi::AVPixelFormat {
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// `Pixel` is `#[repr(i32)]`-compatible with `AVPixelFormat` (the bindgen enum) via this
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// documented conversion in ffmpeg-next.
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ffi::AVPixelFormat::from(p)
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}
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/// Map a captured layout to the NVENC input pixel format, and whether a 3→4 byte expand is
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/// needed (packed RGB/BGR have no padding byte; the NVENC `*0` formats do).
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fn nvenc_input(format: PixelFormat) -> (Pixel, bool) {
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match format {
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PixelFormat::Bgrx => (Pixel::BGRZ, false), // bgr0
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PixelFormat::Rgbx => (Pixel::RGBZ, false), // rgb0
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PixelFormat::Bgra => (Pixel::BGRA, false),
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PixelFormat::Rgba => (Pixel::RGBA, false),
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PixelFormat::Rgb => (Pixel::RGBZ, true), // RGB -> rgb0
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PixelFormat::Bgr => (Pixel::BGRZ, true), // BGR -> bgr0
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}
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}
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pub struct NvencEncoder {
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enc: encoder::video::Encoder,
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/// Reusable 4-bpp CPU input frame (CPU path only; `None` for the zero-copy/CUDA path).
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/// Mutating it in place across frames is sound only because the encoder is opened with
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/// `delay=0`/`bf=0`/`max_b_frames=0` and the caller drains `poll()` after each `submit`,
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/// so libavcodec holds no reference to the previous frame's buffer when we overwrite it.
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frame: Option<VideoFrame>,
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/// Zero-copy path: CUDA hwdevice/hwframes contexts (the encoder takes `AV_PIX_FMT_CUDA`).
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cuda: Option<CudaHw>,
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src_format: PixelFormat,
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expand: bool,
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width: u32,
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height: u32,
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fps: u32,
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/// Monotonic presentation index, in `1/fps` time-base units.
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frame_idx: i64,
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/// Force the next submitted frame to be an IDR (set by [`request_keyframe`]).
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force_kf: bool,
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}
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// `CudaHw` holds raw `AVBufferRef`s; the encoder lives on a single thread. The CPU encoder is
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// already `Send` via ffmpeg-next; assert it for the CUDA fields too.
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unsafe impl Send for NvencEncoder {}
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impl NvencEncoder {
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pub fn open(
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codec: Codec,
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format: PixelFormat,
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width: u32,
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height: u32,
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fps: u32,
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bitrate_bps: u64,
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cuda: bool,
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) -> Result<Self> {
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ffmpeg::init().context("ffmpeg init")?;
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let name = codec.nvenc_name();
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let av_codec = encoder::find_by_name(name)
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.ok_or_else(|| anyhow!("{name} not built into libavcodec"))?;
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let (nvenc_pixel, expand) = nvenc_input(format);
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let mut video = codec::context::Context::new_with_codec(av_codec)
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.encoder()
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.video()
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.context("alloc video encoder")?;
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video.set_width(width);
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video.set_height(height);
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video.set_format(nvenc_pixel); // NVENC converts RGB→YUV internally
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video.set_time_base(Rational(1, fps as i32));
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video.set_frame_rate(Some(Rational(fps as i32, 1)));
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video.set_bit_rate(bitrate_bps as usize);
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video.set_max_bit_rate(bitrate_bps as usize);
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video.set_gop(fps.saturating_mul(2).max(1)); // ~2s keyframe interval
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video.set_max_b_frames(0);
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// For the zero-copy path, take CUDA surfaces: wrap the shared CUcontext in CUDA
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// hwdevice/hwframes contexts and set `pix_fmt = CUDA` on the raw encoder context
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// *before* open (NVENC derives the device from `hw_frames_ctx`).
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let cuda_hw = if cuda {
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let cu_ctx = crate::zerocopy::cuda::context().context("shared CUDA context")?;
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let hw = unsafe { CudaHw::new(cu_ctx, nvenc_pixel, width, height)? };
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unsafe {
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let raw = video.as_mut_ptr();
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(*raw).pix_fmt = ffi::AVPixelFormat::AV_PIX_FMT_CUDA;
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(*raw).hw_device_ctx = ffi::av_buffer_ref(hw.device_ref);
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(*raw).hw_frames_ctx = ffi::av_buffer_ref(hw.frames_ref);
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}
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Some(hw)
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} else {
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None
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};
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// Low-latency NVENC tuning (plan §7 / linux-setup doc).
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let mut opts = Dictionary::new();
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opts.set("preset", "p1"); // fastest
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opts.set("tune", "ull"); // ultra-low-latency
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opts.set("rc", "cbr");
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opts.set("bf", "0");
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opts.set("delay", "0");
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let enc = video
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.open_with(opts)
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.with_context(|| format!("open {name} ({width}x{height}@{fps}, {bitrate_bps} bps)"))?;
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let frame = if cuda {
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None
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} else {
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Some(VideoFrame::new(nvenc_pixel, width, height))
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};
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Ok(NvencEncoder {
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enc,
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frame,
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cuda: cuda_hw,
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src_format: format,
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expand,
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width,
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height,
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fps,
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frame_idx: 0,
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force_kf: false,
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})
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}
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}
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impl Encoder for NvencEncoder {
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fn submit(&mut self, captured: &CapturedFrame) -> Result<()> {
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anyhow::ensure!(
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captured.width == self.width && captured.height == self.height,
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"captured frame {}x{} != encoder {}x{}",
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captured.width,
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captured.height,
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self.width,
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self.height
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);
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let pts = self.frame_idx;
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self.frame_idx += 1;
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// Force an IDR when requested (client RFI); otherwise let NVENC pick (GOP/P-frame).
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let idr = self.force_kf;
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self.force_kf = false;
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match &captured.payload {
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FramePayload::Cuda(buf) => self.submit_cuda(buf, pts, idr),
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FramePayload::Cpu(bytes) => self.submit_cpu(bytes, captured.format, pts, idr),
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}
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}
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fn request_keyframe(&mut self) {
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self.force_kf = true;
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}
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fn poll(&mut self) -> Result<Option<EncodedFrame>> {
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let mut pkt = Packet::empty();
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match self.enc.receive_packet(&mut pkt) {
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Ok(()) => {
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let data = pkt.data().map(|d| d.to_vec()).unwrap_or_default();
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let pts = pkt.pts().unwrap_or(0).max(0) as u64;
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let pts_ns = pts * 1_000_000_000 / self.fps as u64;
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Ok(Some(EncodedFrame {
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data,
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pts_ns,
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keyframe: pkt.is_key(),
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}))
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}
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// No packet ready yet (need another input frame).
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Err(ffmpeg::Error::Other { errno })
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if errno == ffmpeg::util::error::EAGAIN
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|| errno == ffmpeg::util::error::EWOULDBLOCK =>
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{
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Ok(None)
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}
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// Fully drained after flush().
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Err(ffmpeg::Error::Eof) => Ok(None),
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Err(e) => Err(e).context("receive_packet"),
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}
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}
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fn flush(&mut self) -> Result<()> {
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self.enc.send_eof().context("send_eof")?;
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Ok(())
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}
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}
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impl NvencEncoder {
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/// CPU path: expand/copy the packed RGB/BGR bytes into the reusable 4-bpp frame, then send.
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fn submit_cpu(&mut self, bytes: &[u8], format: PixelFormat, pts: i64, idr: bool) -> Result<()> {
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anyhow::ensure!(
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format == self.src_format,
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"captured format {:?} != encoder source {:?}",
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format,
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self.src_format
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);
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let w = self.width as usize;
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let h = self.height as usize;
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let src_bpp = self.src_format.bytes_per_pixel();
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let src_row = w * src_bpp;
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anyhow::ensure!(
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bytes.len() >= src_row * h,
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"captured buffer {} bytes < required {}",
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bytes.len(),
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src_row * h
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);
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let frame = self
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.frame
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.as_mut()
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.context("CPU frame missing (encoder opened in CUDA mode)")?;
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let stride = frame.stride(0); // dst is 4-bpp, aligned
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let dst = frame.data_mut(0);
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if self.expand {
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// packed 3-bpp RGB/BGR → 4-bpp *0 (copy 3 bytes, zero the pad byte)
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for y in 0..h {
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let s = &bytes[y * src_row..y * src_row + src_row];
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let drow = &mut dst[y * stride..y * stride + w * 4];
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for x in 0..w {
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drow[x * 4..x * 4 + 3].copy_from_slice(&s[x * 3..x * 3 + 3]);
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drow[x * 4 + 3] = 0;
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}
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}
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} else {
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// 4-bpp → 4-bpp, honoring the (possibly larger) dst stride
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for y in 0..h {
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dst[y * stride..y * stride + src_row]
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.copy_from_slice(&bytes[y * src_row..y * src_row + src_row]);
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}
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}
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frame.set_pts(Some(pts));
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frame.set_kind(if idr {
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ffmpeg::picture::Type::I
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} else {
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ffmpeg::picture::Type::None
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});
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self.enc.send_frame(frame).context("send_frame")?;
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Ok(())
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}
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/// Zero-copy path: wrap the imported CUDA device buffer in an `AV_PIX_FMT_CUDA` frame and
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/// send it straight to NVENC (no CPU touch). `buf.ptr` aliases device memory we own, so
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/// `buf[0]` is left null (ffmpeg must not free it); the frame shell is freed after send.
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fn submit_cuda(
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&mut self,
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buf: &crate::zerocopy::DeviceBuffer,
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pts: i64,
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idr: bool,
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) -> Result<()> {
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let frames_ref = self
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.cuda
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.as_ref()
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.context("CUDA hw context missing (encoder opened in CPU mode)")?
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.frames_ref;
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unsafe {
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let mut f = ffi::av_frame_alloc();
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if f.is_null() {
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bail!("av_frame_alloc failed");
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}
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(*f).format = ffi::AVPixelFormat::AV_PIX_FMT_CUDA as c_int;
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(*f).width = self.width as c_int;
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(*f).height = self.height as c_int;
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(*f).hw_frames_ctx = ffi::av_buffer_ref(frames_ref);
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(*f).data[0] = buf.ptr as *mut u8;
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(*f).linesize[0] = buf.pitch as c_int;
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(*f).pts = pts;
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(*f).pict_type = if idr {
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ffi::AVPictureType::AV_PICTURE_TYPE_I
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} else {
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ffi::AVPictureType::AV_PICTURE_TYPE_NONE
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};
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let r = ffi::avcodec_send_frame(self.enc.as_mut_ptr(), f);
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ffi::av_frame_free(&mut f);
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if r < 0 {
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bail!("avcodec_send_frame(CUDA) failed ({r})");
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}
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}
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Ok(())
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}
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}
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