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Fourier — initial dossier + plan

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Umbrella for HW-assisted video decode across fresnel/ohm/boltzmann/ampere.
Captures Path A (mainline V4L2 stateless) vs Path B (Rockchip MPP vendor),
rkvdec mainline status as of 2026-04-24 (VDPU381/383 landed Feb 2026;
VDPU346 for RK356x still pending), the 2023 working recipe from
clehaxze.tw, plan for ohm as first priority, and working-agreement
reminders (ReCAP, commit-per-experiment, ask-before-flash/reboot,
off-machine backups).
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Markus Fritsche
2026-04-24 18:46:07 +00:00
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# 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.
## 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.
## 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)