claude-noether
b3ba157cb4
Phase 2 source-read of the HEVC path post-iter1-close (fork master
229d6d1). Six bugs identified, all in libva backend; kernel + driver
path proven for HEVC in Phase 0 cross-validator sweep.
Substrate timing caveat: Phase 2 conducted against fresnel kernel
6.19.9-99. Operator-scheduled rolling pacman -Syyuu to linux-7
imminent. Phase 2 source-read findings are kernel-agnostic (fork
code + UAPI + FFmpeg reference); they carry forward across the
kernel jump unchanged. Phase 3 baselines will run on linux-7.
Bug 1 — src/config.c:64-69 HEVCMain falls through to default,
returns VA_STATUS_ERROR_UNSUPPORTED_PROFILE. Verbatim match for
iter1 Bug 1 pattern; fix is 3-line break addition.
Bug 2 — src/picture.c:204-206 explicit
case VAProfileHEVCMain: return UNSUPPORTED_PROFILE
with stale comment "Fourier-local: HEVC stripped, no HW support
on RK3566." (RK3566 is ohm context; fresnel is RK3399 where
rkvdec DOES support HEVC.) Fix: replace explicit reject with
dispatch to h265_set_controls() (mirrors MPEG-2 dispatch at
picture.c:186-191).
Bug 3 — src/h265.c uses staging-era CIDs:
V4L2_CID_MPEG_VIDEO_HEVC_PPS / _SPS / _SLICE_PARAMS
These don't exist on fresnel's 6.19 kernel headers (verified via
test-compile: gcc reports undeclared identifiers, suggests
V4L2_CID_MPEG_VIDEO_DEC_PTS as nearest match). Mainline kernel
UAPI splits HEVC stateless into 7 controls:
V4L2_CID_STATELESS_HEVC_{SPS,PPS,SLICE_PARAMS,SCALING_MATRIX,
DECODE_PARAMS,DECODE_MODE,START_CODE}
+ ENTRY_POINT_OFFSETS, EXT_SPS_ST_RPS, EXT_SPS_LT_RPS
(0xa40a90..0xa40a96 + extensions, V4L2_CID_CODEC_STATELESS_BASE
+ 400..407+).
Fix shape: rewrite h265.c against new split API. Substantially
larger than iter1's mpeg2.c rewrite (HEVC has 7 controls vs MPEG-2
3, + slice_params dynamic-array, + per-slice accumulation logic
needed).
Bug 4 — h265.c uses single-slice_params shape; new API is
dynamic-array. Fresnel rkvdec advertises:
hevc_slice_parameters 0xa40a92 elems=1 dims=[600] dynamic-array
Up to 600 slice_params entries per submission. Current
codec_store_buffer:115-135 OVERWRITES previous slice on
VASliceParameterBufferType arrival. Multi-slice frames need
APPEND-not-overwrite. FFmpeg reference v4l2_request_hevc.c:540-547
shows the pattern.
Fix shape: extend params.h265 to hold slice_params array (or
pointer+count); codec_store_buffer appends; h265_set_controls
flushes the array at end_picture as a single dynamic-array
S_EXT_CTRLS entry.
Bug 5 — h265.c missing controls: doesn't submit DECODE_PARAMS
(per-frame DPB info; new in modern API), SCALING_MATRIX (conditional
on iqmatrix_set + sps.scaling_list_enabled), DECODE_MODE+START_CODE
(device-wide menus, set once per context init).
Fix shape: add h265_fill_decode_params() (DPB ordering from VAAPI
ReferenceFrames[15] — preserve current extraction logic from
h265_fill_slice_params:269-315, route to new struct). Conditional
SCALING_MATRIX from VAIQMatrixBufferHEVC. Device-wide
DECODE_MODE+START_CODE either at first h265_set_controls call or
in extended context.c device-init block.
Bug 6 — src/meson.build comments out 'h265.c' (line 50) and
'h265.h' (line 73). Fix: uncomment both. Trivial.
Bug 7 (verify only) — include/hevc-ctrls.h is a 9-line shim that
just #include <linux/v4l2-controls.h>. Comment dates the
modernization to "linux-media 6.6+". Adds zero value; harmless.
Leave in place per iter1 Phase 5 Nit 6 lower-risk path.
Bug 8 (latent) — picture.c:287 params.h264.matrix_set=false
writes union byte 240. For HEVC: byte 240 lands inside
h265.picture (range [0..604), size 604) — different field than
MPEG-2's chroma_intra_quantiser_matrix. ffmpeg-vaapi's
per-frame VAPictureParameterBufferHEVC re-send overwrites the
corrupted byte before h265_set_controls reads. Latent for
clients that reuse a surface without re-sending picture params.
iter2+ Phase 4 cross-cutting backlog candidate; not iter2 scope.
Things verified NOT bugs:
- h265_fill_pps/sps/slice_params field extraction from VAAPI
structs is sound (just routes to wrong destination structs)
- NAL header parsing (data_bit_offset bit-search) is preserved
in new API — slice_params still has bit_size + data_bit_offset
- v4l2_set_controls batching API in place (used by H.264 + iter1
MPEG-2; iter2 uses same)
Substrate / kernel observation:
- Linux mainline 7.1.0-rc2 reference checkout has
drivers/staging/media/rkvdec/ with rkvdec.c, rkvdec-h264.c,
rkvdec-vp9.c — NO rkvdec_hevc.c. fresnel's HEVC support is
out-of-tree (Christian Hewitt patches per phase0_findings.md
external references). May land in stable 7.x.
- Phase 4 contract-before-code therefore can't cite kernel-side
HEVC handler source until/unless rkvdec_hevc.c lands in
mainline. UAPI doc + FFmpeg reference + Phase 3 cross-validator
bytes are the contract anchor.
Open questions tabled for Phase 3 (post-linux-7-upgrade):
1. iter1 + T4 references on linux-7 (regression check of closed
iter1 work)
2. SDDM watchpoint on linux-7
3. Cross-validator HEVC re-anchor (Baseline C equivalent for
HEVC) — verbatim payload bytes for SPS, PPS, DECODE_PARAMS,
SLICE_PARAMS array, SCALING_MATRIX
4. Pre-fix scratch test (Bug 1 + Bug 2 only, h265.c kept
commented out) — confirm collateral safe
5. Slice-count for bbb_720p10s_hevc.mp4 fixture
6. Whether linux-7 brings rkvdec_hevc.c into mainline
Predicted iter2 close shape: trivial Bugs 1+2+6 fixes + sizable
h265.c rewrite (~250-400 lines, ~3x iter1's mpeg2.c) + new
codec_store_buffer slice accumulation logic. If Phase 7 fails:
likely struct-size mismatch (run pahole), DPB ordering, or
slice_params array size encoding.
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.