Module encode 

Thin VA-API H.264 encoder built on the vendored libva binding.

Reuses the backend-agnostic bitstream layer (crate::codec::h264) from discord/cros-codecs (BSD-3-Clause) for SPS/PPS/slice synthesis, and drives libva directly for surface upload + slice submission, rather than vendoring cros-codecs’s generic multi-backend encoder framework. The per-frame VA buffer population is ported from cros-codecs’s encoder/stateless/h264/vaapi.rs.

Low-latency only: IPPP (no B-frames), one reference frame, matching the VideoToolbox / Media Foundation / NVENC backends in moq-video.

Three ways in, cheapest first:

• Encoder::encode_dmabuf with an NV12 DMA-BUF at the encoder’s size encodes the producer’s memory in place.
• Encoder::encode_dmabuf with any other importable DMA-BUF (packed RGB from a screen capture, YUYV from a camera, NV12 at another size) converts and scales it into the encoder’s own surface with the video processor, on the GPU.
• Encoder::encode_nv12 uploads CPU pixels.

Checked on Intel Meteor Lake with the iHD driver by decoding with ffmpeg’s software decoder: CPU and DMA-BUF input come back above 35 dB luma PSNR, and BGRX converts to BT.601 and BT.709 with every channel within 6 code values of the reference. The low-power entrypoint is untested, since that device exposes the full one.

Structs

Config

H.264 encoder configuration. Dimensions must be even (4:2:0 chroma).

Encoder

A VA-API H.264 encoder. Built once, fed NV12 frames, emits Annex-B H.264.

Enums

IsReference

Whether a frame is used as a reference, and for how long. (Vendored from discord/cros-codecs, BSD-3-Clause; used by the slice synthesizer.)

Constants

RATE_CONTROL_WINDOW_MS

Window over which libva’s rate controller targets the configured bitrate.

Functions

probe

Checks that display’s driver can encode H.264, which is what Encoder::new needs of a render node.