Pierre Rouanet 9cfd24e49f Build the robot's GStreamer plugins natively, from pinned sources

Two plugins the micro duck robot needs and no archive provides:
`libgstrockchipmpp.so` for hardware H.264 through Rockchip MPP, and
`libgstrswebrtc.so`/`libgstrsrtp.so` for webrtcsink. Debian ships no Rockchip
encoder in any suite, Radxa's prebuilt plugin is decode-only (measured on a
Zero 3W: mppvideodec and mppjpegdec, nothing else — 1.14.4 predates the
encoders), and gstreamer1.0-plugins-rs exists in no Debian suite at all.
`webrtcbin` is deliberately absent: Debian has it.

Native arm64 in a debian:trixie container, which is the point. The daemon
cross-compiles with cargo-zigbuild and its one C dependency is already the
documented cost of that; GStreamer would be a far larger second one, and both
routes — x86 multiarch or a sysroot with a meson cross file — link against an
approximation of the target rather than the target. Here nothing is
approximated.

Public because arm64 runners are free on public repositories, and more
importantly because a release asset is fetched by the updater's preinstall
hook, which runs with a cleared environment and no token. That is the same
arrangement the daemon already relies on for ONNX Runtime.

Pins are commits or tags, never branches, in one file both the build and the
release manifest read — a plugin whose version nobody can name is what makes a
media bug unreproducible, which is exactly what the third-party debs we
rejected could not answer. gst-plugins-rs is pinned at 0.15.3 rather than the
0.14.5 the reachy_mini SDK documents: 0.14.5 is the floor that matters, since
the tags below it miss a webrtcsink deadlock fix between remote description and
ICE handling, and both series declare a GStreamer v1_22 floor against a robot
running 1.26.2.

Two guards written from reading the trees rather than hoping.
`gst/rockchipmpp/meson.build` ends in `if not mpp_dep.found() → subdir_done()`,
so a missing librockchip-mpp-dev makes meson skip the plugin and *succeed*;
pkg-config is checked first and the .so checked for after. And the Radxa debs
are installed as one closure, because dpkg -i resolves nothing for direct
downloads — learning that one package at a time cost three rounds on a board.

Building also drops rkximage and kmssrc, the X11 and KMS sinks in the same
tree, which a headless robot has no use for and which are why the prebuilt deb
depends on libx11-6.

Assisted-by: Claude:claude-opus-5[1m] shellcheck

2026-08-24 16:02:47 +02:00

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microduck-gst-plugins

Prebuilt aarch64 GStreamer plugins for the micro duck robot, built in CI from pinned upstream sources and attached to a release.

Two plugins, for two unrelated reasons. Neither is packaged anywhere we can install from.

plugin	provides	why it is here
`libgstrockchipmpp.so`	`mpph264enc`, `mpph265enc`, `mppjpegenc`, `mppvp8enc`, `mppvideodec`, `mppjpegdec`	Debian ships no Rockchip encoder in any suite, and Radxa's `gstreamer1.0-rockchip1_1.14-4` is decode-only — measured on a Zero 3W: `mppvideodec` and `mppjpegdec`, nothing else. 1.14.4 predates the encoders.
`libgstrswebrtc.so`, `libgstrsrtp.so`	`webrtcsink`, `webrtcsrc`, `rsrtp*`	`gstreamer1.0-plugins-rs` does not exist in any Debian suite — not trixie, backports, sid or experimental.

webrtcbin is not here: it comes from gstreamer1.0-plugins-bad in Debian and needs no build.

Why a repository of its own

The robot's daemon is cross-compiled from a developer's machine with cargo-zigbuild, and its one C dependency is already the documented cost of doing that. GStreamer would be a much larger second one — a cross sysroot or x86 multiarch, either of which links against an approximation of the target.

So these are built natively on an arm64 runner, in a debian:trixie container, which is the robot's own userland. Nothing is cross-compiled and nothing is approximated. arm64 runners are free on public repositories, which is one reason this repository is public.

The other reason matters more: a release asset here is fetched by a robot during provisioning and by the updater's preinstall hook, and that hook runs with a cleared environment and no token. A private repository would break it. This is the same arrangement the daemon already relies on for ONNX Runtime, which comes from a public microsoft/onnxruntime release.

Building rather than taking a third-party binary also buys one concrete thing beyond provenance: rkximage and kmssrc, the X11 and KMS sinks in the same source tree, are disabled. A headless robot has no use for either, and they are why the prebuilt Radxa deb depends on libx11-6.

Consuming a release

tar -xzf microduck-gst-plugins-<version>-aarch64.tar.gz

Put the .so files anywhere and point GST_PLUGIN_PATH at it — /usr/local/lib/gstreamer-1.0 on a robot, which is deliberately not the distro's plugin directory, so an apt operation can never quietly replace or remove them.

GST_PLUGIN_PATH=/usr/local/lib/gstreamer-1.0 gst-inspect-1.0 mpph264enc

Verify the tarball against the .sha256 beside it before unpacking. Pin a version; do not follow "latest". Two provisioning runs a day apart that produce different plugins, with nothing recording which, is an unreproducible media bug waiting to happen.

Runtime dependencies

The plugins link against libraries a robot needs installed:

librockchip-mpp1 and librga2 — from Radxa's pool, at the versions in pins.env. Not in Debian.
libgstreamer1.0-0, libgstreamer-plugins-base1.0-0, libglib2.0-0, libdrm2 — Debian.

mpph264enc also needs read/write access to /dev/mpp_service, which arrives as 0600 root:root. The failure that causes is silent in two different ways: mpi_enc_test writes an empty file and exits 0, and this plugin registers its decoders while omitting the encoders, because registration probes MPP. A non-root process needs a udev rule giving the node a group.

Bumping a pin

Edit pins.env, commit, tag vN, push the tag. The release workflow builds and attaches the tarball, with the manifest as the release notes so a release always says which upstream commits it came from.

workflow_dispatch builds without cutting a release — worth using, because a workflow that only ever runs on a tag is one you discover is broken at the moment you need it.

Licences and source

These are binaries built from other people's source, so where that source is matters:

gstreamer-rockchip is LGPL. Built from JeffyCN/mirrors on the gstreamer-rockchip branch, at the commit in pins.env and recorded in every release's MANIFEST. rockchip-linux/gstreamer-rockchip, which every published deb names as its homepage, is a 404; JeffyCN/mirrors is the live mirror under the same maintainer.
gst-plugins-rs is MPL-2.0. Built from the upstream repository at the tag in pins.env.

Nothing here is modified — no patches, no forks. Each release's MANIFEST names the repository and the exact ref per plugin, which is both the licence answer and the reason a media bug found on a robot can be traced to a specific build.

This repository's own build scripts are Apache-2.0, matching the daemon.

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