# Fourier — Hardware-Assisted Video Decoding on the Rockchip Fleet

One umbrella project to bring up working HW video decode on all four Rockchip
devices in Markus' fleet. Named 2026-04-24.

## Target fleet

| Host      | SoC    | Role                      | Parent umbrella |
|-----------|--------|---------------------------|-----------------|
| fresnel   | RK3399 | Pinebook Pro fleet laptop | —               |
| ohm       | RK3566 | PineTab2 tablet           | —               |
| boltzmann | RK3588 | Rock 5 ITX+ (always on)   | Volta           |
| ampere    | RK3588 | CoolPi GenBook laptop     | Coulomb         |

Current priority: **ohm**. The other three follow in the order of easiest-win
(fresnel, mature mainline) → incremental (ampere, RK3588 landed Feb 2026) →
hardest (boltzmann, currently on vendor kernel).

## Related Rockchip projects

Fourier touches hardware that already has its own umbrellas. Keep display/boot
concerns in those projects; keep video decode in Fourier.

- **Coulomb** — ampere / CoolPi GenBook stack. Subprojects:
  - **Bin** — u-boot, display bringup (eDP + keyboard)
  - **MegabitChip** — DDR init blob matching-decomp / HIL
  - **RockHard** — mainline kernel (Collabora TF-A, LP5-3200 OC)
- **Volta** — boltzmann / Rock 5 ITX+ stack. Subprojects:
  - **Quark** — edk2-rk3588 UEFI firmware
  - **Neutron** — mainline / vendor kernel, UEFI-booted
- **fresnel** — Pinebook Pro, custom overclocked kernel package (no umbrella)
- **ohm** — PineTab2, DanctNIX base, UART capture rig for ampere DDR work

Cross-cutting notes in `/home/mfritsche/.claude/projects/-home-mfritsche-claude/memory/`
— see `MEMORY.md` for the index.

## Meet His

When Fourier needs infra muscle (wake a sleeping host, reach a VPN peer, bump
DHCP on the Fritz, find the right lmcp token, set up distcc for a kernel
build), summon **His** — the Home Infrastructure Specialist.

- As a subagent: `Agent(subagent_type: "his", prompt: "...")` — takes over a
  task end-to-end and returns a report.
- As a skill: `Skill(skill: "his")` — loads the runbook cheatsheet into the
  current session.

His knows the distcc workers (tesla, CT108, dcc1), the Fritz!DECT plug blast
radii (careful with Himbeere + Office), the `/opt/herding/` layout on hertz,
the lmcp endpoint token map, and the VPN naming (`<host>.vpn` via shannon's
dnsmasq). Canonical runbook: `/home/mfritsche/claude/CLAUDE.md` on noether.

For Fourier specifically, expect to lean on His for: waking ohm over LAN +
VPN, confirming ampere is at .vpn (not the stale .88.x LAN IP), setting up
cross-builds of patched ffmpeg via distcc, and nudging kernel packages into
the marfrit repo.

## Two kernel paths

Rockchip hardware decode has **two incompatible kernel driver families**.
Userspace config diverges accordingly — don't mix flags.

### Path A — mainline V4L2 stateless

- Kernel: `rkvdec` / `rkvdec2` stateless V4L2 drivers (mainline or out-of-tree
  patch series).
- /dev node: V4L2 m2m `/dev/videoN` with compressed H.264/HEVC/VP9 queues +
  uncompressed output queue.
- FFmpeg: `ffmpeg-v4l2-request-git` from AUR (Jernej's patchset). Upstream
  v2 patchset posted on ffmpeg-devel 2024-08, **not yet merged** as of
  2026-04-24.
- GStreamer: `v4l2codecs` plugin in gst-plugins-bad. 1.26 added Rockchip
  buffer formats; 1.28 added the new HEVC UAPI controls.
- mpv: `mpv --hwdec=drm --vo=gpu-next` (wayland compositor) or
  `--vo=dmabuf-wayland` (wlroots).
- Kodi: native V4L2-request API support, independent of FFmpeg.
- VA-API: `libva-v4l2-request` bridge for Firefox / Chromium paths.

### Path B — Rockchip MPP vendor

- Kernel: `mpp_rkvdec` / `mpp_rkvdec2` from Rockchip BSP (the rkr* kernel
  series).
- /dev node: `/dev/mpp_service` chardev, not V4L2.
- FFmpeg: build with `--enable-rkmpp` against `librockchip-mpp`.
- GStreamer: Rockchip-specific plugins (`rkximagesink`, `mppvideodec`, …).
- Present today on **boltzmann** (kernel 6.1.75-rkr3).

## rkvdec mainline status (2026-04-24)

| SoC     | Block              | Mainline status              | Codecs (mainline)                                    |
|---------|--------------------|------------------------------|------------------------------------------------------|
| RK3399  | Hantro G1/G2       | mature                       | MPEG-2, VP8, H.264, HEVC, VP9                        |
| RK3566  | rkvdec2 (VDPU346)  | **not yet** (Collabora TODO) | rkvdec1: MPEG-2/VP8/H.264; HEVC/VP9 need out-of-tree |
| RK3588  | VDPU381            | **merged 2026-02-27**        | H.264, H.265 (no VP9/AV1 upstream yet)               |
| RK3576  | VDPU383            | merged 2026-02-27            | H.264, H.265                                         |

The RK3588 / RK3576 landing was the Feb 2026 Collabora drop. VDPU346 for the
RK356x family is on the roadmap but not merged; ohm depends on DanctNIX
carrying out-of-tree rkvdec2 patches if we want HEVC/VP9.

## ohm — first priority, known recipe

From Martin Chang's blog (clehaxze.tw, 2023, still mirrored by DanctNIX):

```sh
sudo pacman -S mpv
yay -S ffmpeg-v4l2-request-git
mpv --hwdec=drm --vo=gpu-next --wayland-disable-vsync=yes input.mp4
# wlroots compositor variant:
mpv --hwdec=drm --vo=dmabuf-wayland input.mp4
```

2023 coverage: **MPEG-2, VP8, H.264**. 1080p60 H.264 hit ~80% of one CPU core
— decode was on the hardware; the CPU was in the compositor path.

**Open question**: does the current linux-pinetab2 6.15-danctnix2 carry
out-of-tree rkvdec2 patches for HEVC/VP9, and if so, does the 2023 recipe
still work verbatim? Next live recon on ohm answers this.

### Plan (tasks #18–24 in the noether task list)

1. **Live recon** — kernel, `/dev/video*`, `v4l2-ctl --list-devices`, dmesg
   rkvdec, `/lib/firmware/rockchip/`, installed ffmpeg/gstreamer/mpv/kodi
2. **SW baseline** — 1080p H.264 / HEVC / VP9 benchmark with ffmpeg and mpv
   hwdec=no, record CPU% + fps
3. **Driver binding** — confirm V4L2 stateless decode node exposed; if not,
   diagnose kconfig / DT / firmware
4. **GStreamer v4l2codecs** — cleanest proof; `v4l2slh264dec` pipeline with
   `fakesink`, then with display sink
5. **FFmpeg v4l2-request** — install `ffmpeg-v4l2-request-git` (AUR) or
   verify a DanctNIX-shipped ffmpeg with v4l2-request enabled
6. **Kodi + mpv validation** — 1080p HEVC at <30% of one core target
7. **Document** — freeze the final recipe in this README

**Current blocker**: ohm offline. Last known VPN state — only `nc` connected;
LAN gives "No route to host" for `ohm.fritz.box` (192.168.88.168). Ask
Markus to wake / reach out when ready.

### Acceptance criterion

**1080p @ 30 fps, no dropped frames.** Applies to every device and every
codec we claim support for. Same bar everywhere — don't grade RK3566 on a
curve vs RK3588. Dropped-frame count comes from `mpv --msg-level=all=info`
or `ffmpeg -f null -`; "no dropped frames" means zero across a 60 s clip.

### Test corpus

**Big Buck Bunny** is the canonical open test clip (Blender Foundation 2008,
CC-BY), ubiquitous in HW-decode testing across a decade of embedded
silicon. Various encodes readily available at
[peach.blender.org](https://peach.blender.org/download/) and mirrors.

Plan: park a fixed set on doppler under `/moviedata/fourier-test/` so Gerbera
re-indexes it and every fleet device on LAN + VPN streams identical bits.
Canonical encodes:

| File                          | Codec  | Res   | Notes                        |
|-------------------------------|--------|-------|------------------------------|
| bbb_1080p30_h264.mp4          | H.264  | 1080p | covers all four devices      |
| bbb_1080p30_hevc.mp4          | HEVC   | 1080p | ampere/boltzmann full; ohm pending rkvdec2 |
| bbb_1080p30_vp9.webm          | VP9    | 1080p | ohm pending; RK3588 pending upstream |
| bbb_1080p30_mpeg2.ts          | MPEG-2 | 1080p | Path A fresnel + rkvdec1 baseline |
| bbb_1080p30_vp8.webm          | VP8    | 1080p | fresnel + RK356x rkvdec1 baseline |
| bbb_2160p60_hevc.mp4          | HEVC   | 4K60  | RK3588 stretch goal (ampere/boltzmann only) |

Stretch: add **Tears of Steel** (2012, also CC-BY) for HDR / high-bitrate
HEVC once the stretch goal is viable.

## After ohm

- **ampere** (RK3588) — once RockHard kernel tracks a tree with VDPU381
  merged (>= Linux 6.14-ish with the Feb 2026 backport), add `v4l2codecs` and
  `ffmpeg-v4l2-request` packaging to RockHard's output. Should be a small
  step.
- **boltzmann** (RK3588) — dual-path decision. Short-term: use Path B with
  rkmpp (the kernel already exposes it). Long-term: migrate Neutron to a
  mainline kernel with VDPU381 and move to Path A for symmetry with ampere.
- **fresnel** (RK3399) — Hantro is mature upstream; likely only needs
  userspace install + recipe validation. Endeavour OS package names TBD.

Patches upstreamed along the way (v4l2-request to FFmpeg, VDPU346 to
linux-media) count double — they benefit the whole fleet.

## Known gotchas / watch-for

Sign-posting only — details in linked sources. If you hit one of these,
expand the bullet with your specific find.

- **IOMMU faults.** Collabora's Feb 2026 VDPU381 landing included specific
  IOMMU fixes. If dmesg shows rockchip-iommu faults during decode, check
  you're on a kernel that carries the fixes, not just the driver.
  ([Collabora post](https://www.collabora.com/news-and-blog/news-and-events/rk3588-and-rk3576-video-decoders-support-merged-in-the-upstream-linux-kernel.html))
- **Firmware blob.** rkvdec / rkvdec2 need a firmware file under
  `/lib/firmware/rockchip/` (varies by SoC). Missing blob → driver probe
  fails silently (no /dev/videoN). Check linux-firmware package currency.
- **HEVC UAPI version gating.** New explicit RPS controls arrived with
  the Feb 2026 landing; GStreamer 1.28 + FFmpeg-preliminary honour them.
  Older userspace on a newer kernel (or vice versa) fails in unintuitive
  ways. Pin both sides when diagnosing.
- **Compositor-bound ≠ decode-bound.** The 2023 clehaxze result saw 80%
  CPU at 1080p60 H.264 — that was the compositor + dmabuf path, not
  decode. Always attribute CPU with `perf top` / `top -H` before calling
  decode slow. Use `mpv --vo=null` to isolate the decode path.
- **VOP2 cfg_done (RK3588).** Decoded frames appear via VP0/VP1/VP2; if
  the shadow-register latch dance is wrong, frames don't show. See
  `feedback_rk3588_cfg_done.md` + `project_bin_vp0_theory.md` in noether
  memory. Touches Coulomb / Bin territory — if it gets there, ask.
- **Multi-core VDPU381 on RK3588.** Silicon has two decoder cores;
  upstream multi-core support is still landing. Until then, ampere /
  boltzmann run on one core and under-deliver vs headline specs.

## Build infrastructure

Fourier touches two kinds of builds: userspace (FFmpeg + patches, GStreamer,
libva-v4l2-request) and kernel (DT + module compiles if we carry out-of-tree
rkvdec2 / VDPU346). Both benefit from distcc — CT108 (14-core aarch64 on
data, wake via `wake-data` on hertz) plus always-on tesla on hertz.

Zeroconf is broken in containers — hand-wire `DISTCC_HOSTS`.

### Kernel / DT modules (cross-build from x86 host)

```sh
DISTCC_HOSTS="localhost/4 192.168.88.208:3632/14,lzo,cpp tesla.lxd:3632/4,lzo,cpp" \
  pump make -j80 O=build/ ARCH=arm64 \
  CROSS_COMPILE='distcc aarch64-linux-gnu-' HOSTCC='ccache gcc'
```

Pump mode sometimes misbehaves on aarch64 cross builds — fall back to plain
`make -j80` without `pump` if include-server throws.

### FFmpeg / userspace (native aarch64 host — ohm, ampere, fermi build CT)

```sh
export DISTCC_HOSTS="localhost/4 192.168.88.208:3632/14,lzo,cpp tesla.lxd:3632/4,lzo,cpp"
export MAKEFLAGS="-j80"
makepkg -s                    # AUR / marfrit-packages workflow
# or, from raw tree:
./configure && pump make -j80
```

`makepkg` honours `MAKEFLAGS` but not `DISTCC_HOSTS` for all build hooks —
put `DISTCC_HOSTS` in `/etc/makepkg.conf` or export before invocation. CC/CXX
wrappers: `/usr/lib/distcc/` symlinks on native aarch64 (NOT
`/usr/lib/distcc/bin/`).

Remember to re-run `wake-data` if CT108 is asleep — see `his` skill or the
`project_distcc_infra.md` memory for the full recipe. When that memory and
this README diverge, fix both.

## Packaging — marfrit-packages

New fleet hosts should get Fourier userspace via `pacman -S` / `apt install`,
not per-device AUR rebuilds. Mirror plan in `marfrit-packages` (layout:
`arch/<pkg>/PKGBUILD`, `debian/<pkg>/build-deb.sh + debian/`):

| Package                      | Source                                  | CI runner | Target  |
|------------------------------|-----------------------------------------|-----------|---------|
| `ffmpeg-v4l2-request-git`    | fork of AUR (Jernej's patchset on ffmpeg tip) | **fermi** (Arch ARM aarch64) | Path A: ohm, fresnel, ampere |
| `ffmpeg-v4l2-request`        | same patches against Debian ffmpeg src  | **feynman** (Debian aarch64) | Path A Debian hosts |
| `gst-plugins-bad-fourier`    | only if stock distro package is <1.28   | fermi / feynman | 1.28 HEVC UAPI uplift |
| `libva-v4l2-request`         | upstream tag                            | fermi / feynman | VA-API bridge |

The Arch package is the priority (ohm + fresnel are Arch-based). Debian
package comes second (relevant if a fleet host ever runs Debian — kepler or
similar). Both are `provides=(ffmpeg) conflicts=(ffmpeg)`, so install
deliberately replaces the distro ffmpeg on a given host.

CI trigger on each push. Artifacts land in packages.reauktion.de
(`reference_marfrit_repo_bootstrap.md` in noether memory has the client
bootstrap).

Out of scope: rkmpp-based FFmpeg (Path B). Boltzmann stays on rkr* until
Neutron migrates; that host doesn't need a marfrit-packages entry until
migration.

## Upstreaming policy

**Default: upstream-first.** Anything generic (FFmpeg v4l2-request polish,
GStreamer fixes, linux-media DT nodes for rkvdec2 / VDPU346 on RK356x,
kernel compatible-string additions) goes to the relevant maintainer list
(`ffmpeg-devel`, `linux-media`, `linux-rockchip`, `gstreamer-devel`,
gitlab.fd.o) — not to marfrit-packages as a downstream carrier.

**Fallback: when upstream ideology blocks success**, stop fighting the
review. Mark the patch `# NOT FOR UPSTREAM`, carry it in marfrit-packages,
and document it in this README under a "fleet-local patches" section. The
stance then becomes: *Markus has the only devices in the world which are
hardware-decoding-capable, and whoever wants to follow should get a Claude
plan*. Fleet keeps working; replication path is reproducible; no energy
burnt arguing with maintainers who won't merge.

The bar for switching: a concrete rejection on ideological grounds (licensing
stance, design-religion, NIH), not a normal review cycle. Normal review
friction — respin until it lands.

Known RockHard precedent for downstream-only: the `GCC_PLUGINS` patch
(`project_linux_rk3588.md`). Tag new carrier-only patches the same way for
consistency.

## Working agreements

Standing rules for how we run this project — inherited from the broader
collaboration canon (`feedback_*` / `project_*` in noether's memory system),
captured here so a cold-start Fourier session doesn't re-learn them.

### ReCAP — ReContextualization After Pruning

Claude's context gets compacted when long sessions hit the window limit, and
any live-session state not in durable storage vanishes. Our counter:

- Memory files (`/home/mfritsche/.claude/projects/-home-mfritsche-claude/memory/`,
  `MEMORY.md` is the index) are the long-term substrate. Don't keep
  load-bearing facts only in conversation.
- Project READMEs (this file) carry the research dossier + current plan.
  Update them when state changes, not later.
- Task list on noether carries active work. Status transitions are cheap —
  mark in_progress when starting, completed when done.
- After a `/compact`, re-read relevant memory files + README + recent git log
  before reasoning. Don't infer from conversation alone.

See `project_recap.md` in memory for the full protocol.

### Commit per experiment

Every experiment that touches the tree — a kconfig change, a DT tweak, a
ffmpeg build flag, a test clip benchmark — gets its own commit on a WIP
branch, with a short message naming what changed and what was observed.

- Dirty trees are tech debt. If the tree is dirty for >30 min, commit.
- Include benchmark numbers / dmesg excerpts / observation in the commit
  body, not just the code diff.
- Rebase / squash later if a clean series matters; don't delay the commit
  waiting for it.

See `feedback_commit_cadence.md` in memory.

### Ask before flash / reboot

This project spans fleet laptops and always-on hosts. We have **real blast
radius**.

- Never flash anything without a verified, tested backup. Fritz!Box 7490 was
  bricked by flashing with an empty backup on 2026-04-12 — we don't repeat
  that class of mistake. See `feedback_flash_critical.md`.
- Shared hardware reboots pause the user's other work. Ask before rebooting
  data (Proxmox), hertz (home-LAN spine), boltzmann (always-on build host).
  See `feedback_no_bulldoze_reboots.md`.
- For kernel / u-boot / firmware changes: simulate first where possible
  (QEMU, module-style load) before flashing silicon. See
  `feedback_simulate_first.md`.
- **Never** run `update-initramfs` or equivalent on a remote host that boots
  from a non-standard root (ZFS, btrfs-with-subvols). See
  `feedback_initramfs.md`.

### Off-machine backups

Fleet laptops back up to data via backintime (Anacron mode, daily attempts,
VPN-guarded, 30-day staleness alert by email). Hertz backs up to data
weekly / quarterly via `backup-hertz.sh` (vitruvius dashboard shows
progress). Data itself lives on ZFS RAIDZ2 + snapshots.

- Before any invasive change on a fleet laptop, confirm its last successful
  backintime snapshot in `/opt/herding/var/backintime-status/<host>` on
  hertz.
- New per-device state (kernel patch series, ffmpeg build tree) lives in a
  Gitea repo + gets backed up with the rest of the working tree — don't
  leave unique work on a single disk.
- External photos / family data on hertz is mirrored via the hertz backup to
  data. Restore recipe is in the two-step `restore-hertz-step1-sd.sh` /
  `restore-hertz-step2-lxd.sh` on data.

### See also — broader feedback canon

- **Test the observer first** (`feedback_observer_first.md`) — before
  drawing decode-performance conclusions, confirm the rig (v4l2-ctl reports
  sensible caps? ffmpeg actually routing through v4l2request?).
- **Three strikes then verify** (`feedback_three_strikes.md`) — after two
  failed fixes, stop guessing; verify the binary / wire / protocol.
- **TRM or nothing** (`feedback_trm_or_nothing.md`) — register writes need
  documentation backing. Relevant for any DT or driver patches we ship.
- **Trust Markus' eyes** (`feedback_trust_user_eyes.md`) — if he reports
  "it plays smoothly", that's primary evidence. Don't over-qualify.
- **No budget framing** (`feedback_no_budget_framing.md`) — don't pre-shrink
  scope citing "session cost"; Markus sets pace.

## References

### Mainline kernel state
- [Rockchip RK3588 / RK3576 H.264 and H.265 video decoders gain mainline Linux support (CNX Software, 2026-02-27)](https://www.cnx-software.com/2026/02/27/rockchip-rk3588-rk3576-h-264-and-h-265-video-decoders-mainline-linux/)
- [RK3588 and RK3576 video decoders support merged in the upstream Linux Kernel (Collabora)](https://www.collabora.com/news-and-blog/news-and-events/rk3588-and-rk3576-video-decoders-support-merged-in-the-upstream-linux-kernel.html)
- [Upstream support for Rockchip's RK3588: Progress and future plans (Collabora)](https://www.collabora.com/news-and-blog/news-and-events/rockchip-rk3588-upstream-support-progress-future-plans.html)
- [media: rkvdec: Add support for VDPU381 and VDPU383 (LWN)](https://lwn.net/Articles/1053556/)
- [RKVDEC2 Driver Posted For Accelerated Video Decoding On Newer Rockchip SoCs (Phoronix)](https://www.phoronix.com/news/RKVDEC2-Rockchip-Video-Decode)

### FFmpeg V4L2 request API
- [PATCH v2 0/8 Add V4L2 Request API hwaccels for MPEG2, H.264 and HEVC (ffmpeg-devel, 2024-08)](https://ffmpeg.org/pipermail/ffmpeg-devel/2024-August/332034.html)
- [Miouyouyou/FFmpeg-V4L2-Request (build script)](https://github.com/Miouyouyou/FFmpeg-V4L2-Request)
- [ffmpeg v4l2 requests 4.4.3 patchset (artemis.sh, 2023-03)](https://artemis.sh/2023/03/06/ffmpeg-v4l2-requests-4.4.3.html)

### GStreamer v4l2codecs
- [GStreamer v4l2codecs plugin docs](https://gstreamer.freedesktop.org/documentation/v4l2codecs/index.html)
- [Adding VP9 and MPEG2 stateless support in v4l2codecs for GStreamer (Collabora, 2021)](https://www.collabora.com/news-and-blog/blog/2021/06/23/adding-vp9-and-mpeg2-stateless-support-in-v4l2codecs-for-gstreamer/)
- [GStreamer 1.26 — improved hardware efficiency (Collabora)](https://www.collabora.com/news-and-blog/news-and-events/gstreamer-126-improved-hardware-efficiency.html)

### PineTab2 specific
- [Hardware accelerated playback on PineTab 2 (clehaxze.tw, 2023-09)](https://clehaxze.tw/gemlog/2023/09-17-hardware-accelerated-playback-on-pinetab2.gmi)
- [PINE64 Mainline Hardware Decoding wiki](https://wiki.pine64.org/wiki/Mainline_Hardware_Decoding)
- [dreemurrs-embedded/linux-pinetab2 releases (6.15.2-danctnix2 latest)](https://github.com/dreemurrs-embedded/linux-pinetab2/releases)