a9a839f274
webrtcsink's codec discovery builds its encoding chain with no output caps, so `force_profile` is
true and it inserts a capsfilter demanding `profile=constrained-baseline` — WebRTC's interoperable
floor. h264parse strips `alignment`, `stream-format` and `parsed` from a caps query but not
`profile`, so that demand reaches mpph264enc's src pad, whose template listed only
`{ baseline, main, high }`. Empty intersection, GstVideoEncoder's sink getcaps returns nothing,
and the failure surfaces upstream as videorate reporting it "could not transform NV12 ... in
anything we support". Discovery then drops H.264 with a warning nobody was reading, VP8 wins by
default, and the session dies in rtpvp8pay.
The element could always produce constrained-baseline; only its static template denied it.
Measured on an RK3566: `mpph264enc profile=baseline ! h264parse` negotiates
`profile=(string)constrained-baseline` on the parser's src pad, because baseline mode turns CABAC
and 8x8 transform off and MPP emits no FMO, ASO or redundant slices. So this widens the template
by one word rather than claiming something new.
Patches now live in a directory per upstream, applied by an `apply_patches` helper and recorded in
the MANIFEST as `patch <project>/<file>`. Two reasons: a patch aimed at the wrong tree failed the
same way a stale one does, and the MANIFEST's flat `patch <file>` line landed next to whichever
.so happened to precede it, which read as provenance for the wrong plugin.
Assisted-by: Claude:claude-opus-5[1m]
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. Radxa's own gstreamer1.0-rockchip1_1.14-4 does contain them, so this build is about the pin, dropping libx11-6, and riding along with the plugin below — see below. Patched; see patches/. |
libgstrswebrtc.so, libgstrsrtp.so |
webrtcsink, webrtcsrc, rsrtp* |
gstreamer1.0-plugins-rs does not exist in any Debian suite — not trixie, backports, sid or experimental. Patched; see patches/. |
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.
The permission trap that hid all of this
/dev/mpp_service arrives as 0600 root:root, and an MPP GStreamer plugin registers its
decoders unconditionally but probes MPP before registering its encoders. With the node
unreadable the probe fails and the encoders are silently omitted — no error, no log line.
That one cause produced four separate misleading results while this was being worked out:
mpi_enc_testwrote an empty file and exited 0.- Radxa's
1.14-4looked decode-only. It is not;stringson its.solists every encoder. - A third-party
1.14-8deb installed cleanly and still showed nompph264enc. - This repository's own CI build shows only
mppjpegdecandmppvideodec, because a container has no/dev/mpp_serviceeither. That is expected, not a failed build.
So: a plugin that lists only decoders is evidence about the device node, not about the plugin. A
non-root process needs a udev rule giving the node a group — mode 0660, group video — and only
then does gst-inspect-1.0 mpph264enc mean anything.
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-mpp1andlibrga2— from Radxa's pool, at the versions inpins.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 — see
the permission trap, which is the single most
misleading thing about this stack.
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-rockchipis LGPL. Built fromJeffyCN/mirrorson thegstreamer-rockchipbranch, at the commit inpins.envand recorded in every release'sMANIFEST.rockchip-linux/gstreamer-rockchip, which every published deb names as its homepage, is a 404;JeffyCN/mirrorsis the live mirror under the same maintainer.gst-plugins-rsis MPL-2.0. Built from the upstream repository at the tag inpins.env.
Both upstreams are patched, and that matters for more than tidiness. MPL-2.0 asks that
modifications be identifiable, so they are stated here, listed in patches/ with what
each one buys and how it ends, and recorded in every release's MANIFEST — a release names each
upstream ref and every patch applied over it.
Two patches today, both about getting hardware H.264 to a browser:
gst-plugins-rs—webrtcsinkinserts a softwarevideoconvert ! videoscalein front of any encoder it does not recognise, andmpph264encconverts on the SoC's 2D accelerator instead, so a CPU pass over every frame is added to work the hardware was going to do anyway, on cores the robot's control loop shares.gstreamer-rockchip—mpph264enc's pad template omittedconstrained-baselinefrom its profile list, which is the one profile WebRTC asks for. Without this,webrtcsinkcannot offer H.264 on an RK3566 at all, and the only trace is avideoratecomplaining about NV12.
patches/README.md has the reasoning for each, the trade-off it accepts, and
the route upstream that would delete it.
Together the ref and the patch list are 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.