Crate denise_video 

Hardware video decode onto a DRM plane.

A kiosk playing a promo loop is a set-top box with a different sticker, and this crate does what a set-top box does: compressed bytes go to the SoC’s decoder over V4L2 memory-to-memory, decoded frames come back as dmabufs, and each dmabuf is imported as a DRM framebuffer and flipped onto a video plane the display controller composites during scanout. The frame never passes through denise-render at all; the UI keeps painting its own buffer and the plane sits in the stack with it. Zero copies end to end, no ffmpeg, no GStreamer, no C library — the same single-static-binary discipline as denise-drm.

The format menu

Two elementary streams, chosen so every Raspberry Pi hardware-plays at least one: H.264 (Constrained Baseline/Main, Annex-B, .h264) for Pi Zero through 4 and most other embedded SoCs, and HEVC (Main, .h265) for Pi 4 and 5. Both yuv420, at most 1080p30. The board picks: Decoders::detect asks the hardware, Decoders::pick applies the rule, and a kiosk ships both files — two ffmpeg lines at build time instead of one.

No container, no demuxer, no seeking: play, loop and stop, which is what a promo loop is. Audio is a different subsystem and deliberately absent.

What runs where

Everything that talks to /dev is Linux-only and cfg-gated to nothing elsewhere. The Annex-B access-unit logic in annexb is pure and compiled — and tested — everywhere.

Status

The stateful decode path (H.264 via bcm2835-codec on the Pi, and its equivalents on i.MX, Rockchip and Amlogic), verified end to end on a Pi 3A+: access units in, dmabuf out, imported as a DRM framebuffer and flipped onto a plane at a paced 29.5 fps over a live UI surface.

The stateless HEVC path for rpivid — what the Pi 5 needs, and an order of magnitude more work: slice parsing, reference management, the media request API — is #36. Decoders::detect already reports it where the hardware offers it, so a board with rpivid and no bcm2835-codec will say so and then decline to play, which is the honest answer until #36 lands.

Modules

annexb

Annex-B elementary streams, split into what a decoder wants fed.

Structs

Asset

One decodable asset an application offers: a codec and the file that holds its elementary stream.

DecodedFrame

One decoded picture, ready for scanout.

Decoder

A stateful V4L2 decode session on one device node.

DecoderInfo

One decoder node and what it accepts.

Decoders

The board’s decoders, enumerated once.

Player

An elementary stream playing onto a plane.

VideoPlane

A video plane on the surface’s CRTC, fed dmabuf frames.

Enums

VideoError

Video errors: enumeration, negotiation, streaming, scanout.