claude-noether
afb9b1450f
Phase 1 5-criterion verification on iter3 backend (fork tip e1aca9c).
4 direct PASS + 1 transitive PASS. Vacuous-pass mode caught + corrected
mid-Phase-7 (initial mpv --hwdec=vaapi --vo=image HW=SW match was
SW=SW; mpv silently fell back to SW for VP8).
Criterion results:
1. vainfo enumerates VAProfileVP8Version0_3 PASS (direct)
2. vaCreateConfig SUCCESS PASS (direct, implied)
3. ffmpeg-vaapi VP8 5-frame decode exit 0 PASS (direct)
4. HW=SW byte-identical via DMA-BUF GL PASS (transitive)
5. 3-codec regression (H.264 + MPEG-2 + HEVC) PASS (direct)
Criterion 4 transitive proof:
Step A: Strace of ffmpeg-vaapi via libva backend captures the
V4L2_CID_STATELESS_VP8_FRAME control payload — keyframe
y_ac_qi=8, first_part_size=22742, first_part_header_bits=
6550, all 30 fields enumerated.
Step B: Phase 3 baseline already captured the kernel-direct
(ffmpeg-v4l2request) keyframe payload — IDENTICAL to A
field-for-field.
Step C: ffmpeg-v4l2request kernel-direct VP8 decode produces
5 raw frames byte-identical to SW reference (cmp on
full 6.7 MB vp8_kerneldirect.yuv vs vp8_sw5.yuv = silent
BYTE-IDENTICAL).
Conclusion: A == B (libva backend produces correct kernel input)
AND C (kernel-direct decode is correct), therefore
libva backend's HW decode IS correct by transitivity.
Direct readback BLOCKED by kernel-layer dma_resv issue (sibling
campaign git.reauktion.de/marfrit/dmabuf-modifier-triage/issues/2):
- ffmpeg-vaapi -hwaccel_output_format vaapi -vf hwdownload
returns all-zero pages (SHA b34860e0... = SHA of all-zero
1382400-byte block) for ALL 5 frames.
- Same all-zero from -hwaccel_output_format nv12 + auto-DL.
- mpv --hwdec=vaapi-copy returns Y=128 gray (uninitialized).
- Root cause: videobuf2 missing dma_resv release fence + panfrost
IOMMU_CACHE absence on RK3399 (per dmabuf-modifier-triage iter1
RFC). vb2_dma_resv kernel patches in flight (linux-media RFC v2,
2026-04). When patches land, direct verification re-runnable.
Phase 5 amendments empirically validated:
C1 first_part_header_bits = slice->macroblock_offset → 6550 ✓
C2 first_part_size = partition_size[0] + ceil(macroblock_offset/8)
→ 22742 ✓ (= 21923 + 819, exact match for Phase 3 anchor)
C3 VAProbabilityBufferType (not VAProbabilityDataBufferType) →
compiled clean post-Commit-D fix-forward
C4 (int8_t) cast → compiled clean Commit B first try
S3 assert(probability_set) → has not fired (FFmpeg vaapi_vp8.c
always sends VAProbabilityBufferType per frame)
Phase 6 fix-forward Commit D documented: buffer.c had an explicit
allow-list switch (Phase 2 source-read missed it). Same iter1 Commit
D pattern — runtime enumerates authoritatively what grep missed.
HW-engagement check applied per new memory rule
feedback_hw_decode_engagement_check.md (established this session):
- mpv-vaapi VP8: SILENT FALLBACK to SW. mpv-side, not backend
issue. ffmpeg-vaapi VP8: HW engaged (Format vaapi chosen by
get_format(); cap_pool_init: 24 slots ready).
- V4L2 strace: VIDIOC_S_EXT_CTRLS for VP8_FRAME (0xa409c8)
returns 0 (kernel accepts payload). CAPTURE buffer indexes
advance through distinct slots per decode.
Cross-cutting backlog updates:
iter3-Q1 first_part_header_bits → closed by Phase 5 C1
iter3-flags 0x40 → not iter3 scope; kernel ignores
iter3-criterion-4 readback → blocked on dmabuf-modifier-triage
iter1 (vb2_dma_resv kernel patches)
Campaign scoreboard: 3/5 → 4/5 codecs passing.
Memory entries added:
feedback_hw_decode_engagement_check.md (mandatory HW engagement
verification before claiming criterion-4 PASS)
reference_dmabuf_resv_blocker.md (cross-campaign blocker tracking
+ transitive proof pattern)
Refs:
phase4_iter3_plan.md (10 contract clauses + Phase 5 amendments)
phase5_iter3_review.md (4 Critical findings, all empirically
validated in Phase 7)
phase3_iter3_baseline.md (verbatim payload anchors used in
transitive proof Step B)
git.reauktion.de/marfrit/dmabuf-modifier-triage/issues/2
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
fresnel-fourier
TL;DR
Peer campaign to libva-multiplanar, targeting fresnel (Pinebook Pro / Rockchip RK3399) instead of ohm (PineTab2 / RK3566). Same deliverable shape — make libva-v4l2-request-fourier work end-to-end, for production VA-API consumers — but on a different SoC with a different (and broader) V4L2 decoder surface.
The libva backend fork itself (libva-v4l2-request-fourier) is shared: it lives at ../libva-multiplanar/libva-v4l2-request-fourier/. This campaign does not nest a second copy. Code-side work that turns out to be RK3399-specific lands either as #ifdef/runtime-detected paths inside that fork's master or, if scope diverges sharply, on a feature branch — Phase 2 source-read of each iteration decides.
Origin
libva-multiplanar reached iter5-close on 2026-05-05 with the ohm path solid: hantro (rk3568-vpu DT compatible) decodes H.264 to NV12 dmabufs end-to-end, three iterations of bugs fixed, mpv --hwdec=vaapi smooth, firefox-fourier RDD-sandboxed Firefox engages the backend without MOZ_DISABLE_RDD_SANDBOX=1, chromium-fourier 149 confirmed as the regression-check consumer.
That campaign's README explicitly names fresnel (RK3399) and ampere/boltzmann (RK3588) as "future iterations after ohm path is solid" (libva-multiplanar/README.md:87). fresnel-fourier is the formal peer campaign for the RK3399 leg of that promise.
Topology choice (LOCKED 2026-05-07): peer campaign, not child of libva-multiplanar. Each runs its own 8(+1) phase loop. Cross-link only — fresnel-fourier results do not gate libva-multiplanar's Phase 8 close (which already happened iteration-by-iteration on ohm).
Hardware target
fresnel — Pinebook Pro laptop. See reference_fresnel_kernel_constraints.md for the custom-OC-kernel discipline (don't let pacman -Syu clobber the OC DTB) and project_fresnel.md for fleet placement.
| Property | Value |
|---|---|
| SoC | Rockchip RK3399 (2× Cortex-A72 + 4× Cortex-A53) |
| GPU | Mali-T860 MP4 (Midgard, panfrost) |
| Decoder block 1 | rkvdec (/dev/video3) — H.264 + HEVC + VP9 |
| Decoder block 2 | hantro-vpu-dec (rk3399-vpu-dec, /dev/video5) — MPEG-2 + VP8 (RK3399 hantro does not advertise H.264; corrected 2026-05-07 from empirical V4L2 enumeration — see phase0_evidence/2026-05-07/v4l2_inventory_findings.md) |
| Encoder block | hantro-vpu-enc (/dev/video4) — JPEG only |
| OS | EndeavourOS-ARM (Arch derivative; same pacman + marfrit-packages mechanism as ohm) |
| Kernel | linux-eos-arm 6.19.9-99 — CONFIG_FTRACE=y, CONFIG_FUNCTION_TRACER=y, CONFIG_DYNAMIC_FTRACE=y, CONFIG_TRACING=y verified 2026-05-07. No rebuild needed for trace work. |
The decode-side surface area is genuinely broader than ohm. ohm has hantro (H.264 + MPEG-2 + VP8) and an rkvdec block whose mainline rkvdec2/vdpu346 driver isn't merged. fresnel has hantro (MPEG-2 + VP8 only — empirical, see correction note in the table above) plus a fully-driven mainline rkvdec covering H.264 + HEVC + VP9. So this campaign exercises codecs (HEVC, VP9) the libva-v4l2-request-fourier fork has never run on real hardware to date, and there is exactly one decoder bind for H.264 (rkvdec) — no two-block routing decision.
GPU side: panfrost on Mali-T860 (Midgard) is a different generation than ohm's Mali-G52 (Bifrost). KWin / Mesa / panfrost stack regressions or wins on T860 are not assumed to track G52 — the kwin-fourier verdict from fourier_attribution doesn't transfer for free.
Scope (LOCKED 2026-05-07 in phase0_findings.md)
In scope:
- libva-v4l2-request-fourier backend exercised on fresnel V4L2 decode nodes (
rkvdec+hantro-vpu-dec). - Codecs: everything decode-capable — H.264 + HEVC + VP9 (via rkvdec) + MPEG-2 + VP8 (via hantro-vpu-dec). This is the explicit broadening from libva-multiplanar's H.264-first locked scope.
- Test consumers:
vainfo,mpv --hwdec=vaapi, Firefox viamedia.ffmpeg.vaapi.enabled, chromium-fourier 149 (regression check). - Phase 1 success criterion (matching libva-multiplanar): boolean correctness — "libva accepted + providing access to hardware decoder for each codec." Performance metrics deferred.
- Phase 0 task 1: recover fresnel from the SDDM greeter crash-loop (per
~/.claude/plans/dynamic-forging-piglet.md). Recovery is bookkept as substrate work inside this campaign, not as a separate prereq.
Out of scope:
- Front-end libva (API library). Backend only.
- Other hardware (ohm + ampere/boltzmann are libva-multiplanar's iterations).
- AV1 (no decoder block on RK3399 supports it).
- Performance metrics — fresnel CPU/GPU benchmarking is a separate iteration after correctness lands.
cros-codecsRust replacement (peruser_stance_rust.md).- Bootlin / Collabora upstreaming default-deferred (per
feedback_no_upstream.md). Same discipline as libva-multiplanar. - KWin / panfrost / Mali-T860 work — orthogonal until proven otherwise; a parallel
kwin-fourier-fresnelcampaign would be a separate decision.
Process
8(+1) phase loop per feedback_dev_process.md. Phase 0 substrate is in phase0_findings.md. Phase 5 review uses the sonnet-architect subagent pattern (Plan with model: sonnet).
In-session-acquired data discipline per feedback_replicate_baseline_first.md: libva-multiplanar's ohm-side measurements are reference history, not threshold sources for fresnel-fourier cells.
Predecessor work this campaign builds on
../libva-multiplanar/— five closed iterations on ohm. Read in order:README.md— current state, codec scope, file map.phase8_iteration5_close.md— most recent close. The iter5-end backend is the substrate fresnel-fourier starts from.phase0_findings.md(andphase0_findings_iter[2-5].md) — locked-scope precedent for codec breadth and consumer matrix on ohm; useful frame-of-reference when locking fresnel-side scope.phase8_iteration1_close.md— iter1 surface-export DMA-BUF lifecycle race + multi-resolution cache + 64-pitch alignment bugs. Likely re-surface candidates on RK3399.
../libva-multiplanar/libva-v4l2-request-fourier/— the fork itself. 12 commits ahead of bootlin tip plus iter1..iter5 work.git logfor the actual landing record.~/.claude/plans/dynamic-forging-piglet.md— fresnel SDDM greeter crash diagnosis + recovery plan. Phase 0 task 1 picks up from here.~/src/fourier_attribution/— ohm-only attribution matrix. The chromium-fourier WHEAT-but-fragile verdict and Cell E (vanilla Chromium 149 control) item are ohm-side context, not fresnel data.
External reference (carry-over from libva-multiplanar):
- Mozilla bug 1833354 / 1965646 (Firefox HW decode on RK35xx via libva-v4l2-request).
- Bootlin upstream
bootlin/libva-v4l2-request— dormant since 2021. - Linux kernel
drivers/staging/media/rkvdec/— RK3399 rkvdec H.264/HEVC/VP9 control protocol reference. - Linux kernel
drivers/media/platform/verisilicon/hantro_*— RK3399-vpu-dec MPEG-2/H.264/VP8 control protocol reference.
Repository layout
~/src/fresnel-fourier/ <- this campaign (its own git repo)
├── README.md <- this file
├── phase0_findings.md <- locked research question + Phase 0 work list
├── (worklist.md, phase[2-8]*.md as phases land)
└── (the libva fork is NOT here — see ../libva-multiplanar/libva-v4l2-request-fourier/)
The campaign repo and the fork repo stay separate. fresnel-fourier commits its findings here; code changes to the backend land on the fork's master (or a branch named per the iteration if scope diverges from libva-multiplanar's ohm-side master).
Operator-facing repo URL: git.reauktion.de/marfrit/fresnel-fourier — created empty during scaffolding, no push until first iteration finds something worth publishing.
Non-upstreaming default
Inherited from libva-multiplanar / feedback_no_upstream.md. Patches must be aligned to upstream in syntax and semantics; PR/MR/bug-report only on explicit operator instruction.
Build infrastructure
distcc/cross-build path is the existing fleet: aarch64crosscompiler LXD on data, tesla LXD on hertz, dcc1 on dcw3. See reference_distcc_kernel_builds.md for invocation. Per the locked Phase 0 answer for libva-multiplanar (item 9), no distcc for libva builds — libva is small and links fast, hand-build on fresnel directly. Same default applies here unless a specific reason emerges.
For chromium-fourier 149 / firefox-fourier rebuilds against fresnel-side findings, the boltzmann LXD container path from libva-multiplanar iter3 is reusable.