claude-noether
f720c7784b
Iteration 1 of the campaign 8(+1)-phase loop opens following the
campaign Phase 0 close (b74551b). Per the suggested order in
phase0_evidence/2026-05-07/cross_validator_traces.md, iter1 attacks
MPEG-2 — the cheapest fix in the codec status sweep (mpeg2.c is
already compiled, src/config.c has the case statements, but
vaCreateConfig returns 12 / UNSUPPORTED_PROFILE).
Locked research question:
Make MPEG-2 the second codec to pass boolean-correctness on
fresnel via the libva-v4l2-request-fourier path —
mpv --hwdec=vaapi-copy bbb_720p10s_mpeg2.ts engages the backend
cleanly and DMA-BUF GL import yields HW pixels byte-identical
to a software-decoded reference for the same frames.
Phase 1 success criterion (5 boolean checks, all must be green):
1. vainfo: VAProfileMPEG2Simple + VAProfileMPEG2Main still
enumerated on the hantro env binding (regression check).
2. vaCreateConfig(VAProfileMPEG2Main, VLD): VA_STATUS_SUCCESS.
3. mpv --hwdec=vaapi-copy --frames=2 --vo=null on
bbb_720p10s_mpeg2.ts: engages backend, exit 0, no
"Failed to create decode configuration" lines.
4. mpv --hwdec=vaapi --vo=image (DMA-BUF GL import) at +02s
seek: 2 distinct frames hash-equal to SW reference frames
and hash-differ from each other.
5. T4 H.264 regression: re-run T4 incantation, hashes match
f623d5f7... and 7d7bc6f2... reference values.
Mechanism the question targets:
The kernel + driver path is solid (cross_validator_traces.md —
ffmpeg-v4l2request decodes the same fixture exit 0). vaCreateConfig
rejection must be downstream of src/config.c:64-65's case match
(both VAProfileMPEG2Simple and VAProfileMPEG2Main are present in
the validation switch) but upstream of return-success. Plausible
suspects for Phase 2 source-read:
- V4L2 capability probe (e.g., VIDIOC_TRY_FMT against MG2S) that
fails because the libva backend was bound to /dev/video5 but
is checking format against the wrong codec list.
- Device-discovery routing reaches a default-reject because
bound device didn't match an expected codec-to-device map.
- media_request allocation step fails on /dev/media2 for some
MPEG-2-specific reason.
- iter6/iter7 regression in the dispatch-by-profile path that
broke MPEG-2 silently because nobody on libva-multiplanar
tested it (iter5 close: "MPEG-2 was iter1 backlog, dropped
at iter6 close because A55 CPU handles it fine" — fresnel
runs A53 so the disposition doesn't transfer).
Phase 4 plan must cite the contract before patching, per
feedback_dev_process.md Phase 6 contract-before-code: read kernel
drivers/media/platform/verisilicon/hantro_mpeg2.c, read FFmpeg
downstream libavcodec/v4l2_request_mpeg2.c, state the MPEG-2
control-submission contract explicitly before any code lands.
Predecessor carry-over (state vs data) explicit per
feedback_dev_process.md Phase 0 + feedback_replicate_baseline_first.md:
Carries forward (re-verified in campaign Phase 0):
- iter8 master fork (65969da) installed on fresnel,
vainfo enumeration confirmed
- bbb_720p10s_mpeg2.ts fixture (5.3 MB, MPEG-2 Main, 720p,
10s, MPEG-TS) on fresnel ~/fourier-test/, provenance
documented in test_fixtures.md
- hantro-vpu-dec /dev/video5 + /dev/media2 binding
- Cross-validator anchor: ffmpeg-v4l2request mpeg2 trace
captured (5 S_EXT_CTRLS, 4 REQUEST_ALLOC, 4 DMA_BUF_SYNC)
- T4 reference hashes for H.264 regression check
Does NOT carry forward (re-acquire if needed):
- ohm/RK3568 hantro MPEG-2 behaviour — different kernel
driver variant inside drivers/media/platform/verisilicon/
- Pre-iter6 libva-multiplanar MPEG-2 trace data (untested
at iter6 close)
Open questions inherited:
- Cache-stale vaDeriveImage bug class on RK3399 (T4) —
iter1 uses DMA-BUF GL import for verify; Phase 4 cross-
cutting fix is not iter1-scoped
- Architectural divergence ffmpeg vs our backend (EXPBUF +
DMA_BUF_SYNC vs cap_pool + vaDeriveImage) — Phase 4
design decision, not iter1-blocking
Out-of-scope (LOCKED): HEVC/VP9/VP8 (later iterations); vaDerive
Image cache-stale fix (Phase 4 cross-cutting); chromium-fourier
149 install (Phase 0 follow-up to iter1 substrate, non-gating);
performance metrics (Phase 1+ separate iteration); long-duration
stress (>10s); other MPEG-2 containers beyond MPEG-TS;
upstream engagement.
Iter1 Phase 2 source-read targets:
- src/config.c::RequestCreateConfig (rejection site)
- src/picture.c MPEG-2 dispatch path
- src/mpeg2.c set-controls path
- kernel drivers/media/platform/verisilicon/hantro_mpeg2.c
- FFmpeg downstream libavcodec/v4l2_request_mpeg2.c
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
122 lines
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Markdown
122 lines
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Markdown
# Iteration 1 — Phase 0 (substrate / motivation / inventory) → Phase 1 lock
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Opens 2026-05-07 evening immediately after campaign [`phase0_findings.md`](phase0_findings.md) close (commit `b74551b`). This is the first per-iteration loop on fresnel-fourier; the campaign-level Phase 0 already locked scope (5 codecs, RK3399, `boolean correctness` per codec) and produced the empirical groundwork on which iter1 commits.
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## Locked research question (iteration 1)
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> **"Make MPEG-2 the second codec to pass boolean-correctness on fresnel via the libva-v4l2-request-fourier path — `mpv --hwdec=vaapi-copy bbb_720p10s_mpeg2.ts` engages the backend cleanly and DMA-BUF GL import yields HW pixels byte-identical to a software-decoded reference for the same frames."**
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Pass/fail (boolean):
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1. **Profile enumeration regression check.** `vainfo --display drm --device /dev/dri/renderD128` with the hantro-vpu-dec env binding (`LIBVA_V4L2_REQUEST_VIDEO_PATH=/dev/video5`, `LIBVA_V4L2_REQUEST_MEDIA_PATH=/dev/media2`) continues to list `VAProfileMPEG2Simple` and `VAProfileMPEG2Main`. (Already passes today; this exists to prove iter1 work didn't strip the enumeration.)
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2. **Config creation succeeds.** `vaCreateConfig(VAProfileMPEG2Main, VAEntrypointVLD)` returns `VA_STATUS_SUCCESS`. (Today returns `12 = VA_STATUS_ERROR_UNSUPPORTED_PROFILE`.)
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3. **End-to-end decode engages the backend.** `mpv --hwdec=vaapi-copy --frames=2 --vo=null --no-audio --no-input-default-bindings ~/fourier-test/bbb_720p10s_mpeg2.ts` with the hantro env binding logs the `[vaapi] libva: Trying to open /usr/lib/dri/v4l2_request_drv_video.so` chain, the `Using hardware decoding (vaapi-copy)` confirmation, and exits 0 with no `Failed to create decode configuration` lines.
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4. **Cache-safe pixel verification matches SW reference.** `mpv --hwdec=vaapi --vo=image --frames=2 --start=00:00:02 --vo-image-outdir=/tmp/iter1_mpeg2_hw` and the equivalent `--hwdec=no` SW run produce JPEGs whose `sha256sum` outputs match for both frame 1 and frame 2. The seek to `+02s` (~48 frames into the 10s 720p MPEG-2 fixture) avoids an all-solid-color intro and exercises real bunny content. Frames 1 and 2 must hash-differ between each other (motion content) AND hash-equal across HW vs SW.
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5. **Regression check on H.264.** The T4 re-run incantation against `bbb_1080p30_h264.mp4` continues to pass — H.264 hashes at +30s seek match the reference values from `phase0_evidence/2026-05-07/h264_baseline_trace.md` (`f623d5f7…` for frame 1, `7d7bc6f2…` for frame 2). Iter1 must not break H.264.
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A clean iter1 close has all five checks green. Anything less loops back to Phase 4 per `feedback_dev_process.md` Phase 7 → Phase 4 edge.
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## Mechanism the question targets
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Phase 0 cross-validator sweep ([`phase0_evidence/2026-05-07/cross_validator_traces.md`](phase0_evidence/2026-05-07/cross_validator_traces.md)) established that the kernel + driver path works for all five locked codecs. `ffmpeg -hwaccel v4l2request -i bbb_720p10s_mpeg2.ts` decodes 2 frames to exit 0 — hantro-vpu-dec on `/dev/video5` accepts the `MG2S` (`V4L2_PIX_FMT_MPEG2_SLICE`) request-API contract end-to-end.
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Phase 0 codec-status sweep then established that **our libva backend is the lone broken link**. Reading [`src/config.c`](../libva-multiplanar/libva-v4l2-request-fourier/src/config.c) on the iter8 master tip (`65969da`):
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- `src/config.c:38: #include <hevc-ctrls.h>` — kernel UAPI HEVC headers loaded (used elsewhere for HEVC enumeration).
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- `src/config.c:45: VAStatus RequestCreateConfig(VADriverContextP context, VAProfile profile, …)` — entry point.
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- `src/config.c:64: case VAProfileMPEG2Simple:` and `src/config.c:65: case VAProfileMPEG2Main:` — the profiles ARE in the validation switch.
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- `src/config.c:113: ...VAProfile *profiles, int *profiles_count)` — `RequestQueryConfigProfiles`, the enumerator.
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- `src/config.c:126: profiles[index++] = VAProfileMPEG2Simple;` and `:127: profiles[index++] = VAProfileMPEG2Main;` — both unconditionally enumerated.
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- `src/config.c:164: case VAProfileMPEG2Simple:` and `:165: case VAProfileMPEG2Main:` — present in another switch (likely `RequestQueryConfigEntrypoints`).
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So all the case statements are in place. Yet `vaCreateConfig` rejects with `12 (UNSUPPORTED_PROFILE)`. The rejection must be downstream of the case match — somewhere in `RequestCreateConfig` between line 67 (after the cases) and the function's return. Plausible suspects:
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- A V4L2 capability probe (e.g., `VIDIOC_TRY_FMT` against `MG2S` on the bound device) that fails because the libva backend was bound to `/dev/video5` but is checking the format against the wrong codec list.
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- A device-discovery routing decision that reaches a default-reject because the bound device didn't match an expected codec-to-device map.
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- A `media_request` allocation step that fails with EINVAL on `/dev/media2` for some MPEG-2-specific reason.
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- An iter6 or iter7 regression in the dispatch-by-profile path that broke MPEG-2 silently because nobody on libva-multiplanar tested it (per `phase0_findings.md` carry-over: "MPEG-2 was iter1 backlog in libva-multiplanar, dropped at iter6 close because A55 CPU handles it fine").
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Phase 2 source-read of `RequestCreateConfig` end-to-end + `picture.c` MPEG-2 dispatch + `mpeg2.c` set-controls path will identify the exact rejection site. **Phase 4 plan must cite the contract before patching.** Per `feedback_dev_process.md` Phase 6 contract-before-code: read kernel `drivers/media/platform/verisilicon/hantro_mpeg2.c`, read FFmpeg downstream `libavcodec/v4l2_request_mpeg2.c`, state the MPEG-2 control-submission contract explicitly in the Phase 4 plan or commit message before any code lands.
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## Predecessor carry-over (campaign Phase 0 → iter1)
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### State that carries forward (re-verified in campaign Phase 0)
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- **Hardware**: fresnel RK3399, kernel `6.19.9-99-eos-arm`. Custom OC kernel with `CONFIG_FTRACE=y, CONFIG_FUNCTION_TRACER=y, CONFIG_DYNAMIC_FTRACE=y, CONFIG_TRACING=y` (`phase0_findings.md` line 29). No rebuild needed.
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- **Hantro-vpu-dec node**: `/dev/video5` + `/dev/media2` bind. DT compatible `rockchip,rk3399-vpu`. Same parent device as the JPEG encoder on `/dev/video4`. Card type: `rockchip,rk3399-vpu-dec` (per `v4l2-ctl --info`).
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- **Decoder formats** (from `phase0_evidence/2026-05-07/v4l2_inventory.txt`): OUTPUT_MPLANE = `MG2S` (MPEG-2 Parsed Slice Data, compressed) + `VP8F`. CAPTURE_MPLANE = `NV12`.
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- **Stateless control payloads** (kernel surface): `mpeg_2_sequence_header` (`0x00a409dc`), `mpeg_2_picture_header` (`0x00a409dd`), `mpeg_2_quantisation_matrices` (`0x00a409de`). All flagged `unsupported payload type` by `v4l2-ctl --list-ctrls-menus` (normal — v4l2-ctl can't serialize compound controls; the kernel ABI uses `VIDIOC_S_EXT_CTRLS` with `V4L2_CTRL_WHICH_REQUEST_VAL`).
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- **Userspace**: libva 1.23.0, libdrm 2.4.131, mpv 0.41.0 stock (replaced mpv-git which was libplacebo-broken; `phase0_evidence/2026-05-07/h264_baseline_trace.md`), ffmpeg `n8.1-13-gb57fbbe50c` (Kwiboo `v4l2-request-n8.1` branch).
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- **Backend build state**: libva-v4l2-request-fourier master tip `65969da` (iter8 Phase 4) built directly on fresnel via `meson setup --prefix=/usr build && ninja -C build && sudo ninja -C build install`. Installed at `/usr/lib/dri/v4l2_request_drv_video.so`, mode 0755 root:root, BuildID `89addcc37a8e6ed2240b0e7ef78789a2e09a2245`, single export `__vaDriverInit_1_23`. Compiled-in codecs: `mpeg2.c`, `h264.c`, `h264_slice_header.c`. Excluded: `h265.c` (commented out in `src/meson.build`). Absent: VP8, VP9 source files.
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- **Test fixture**: `~/fourier-test/bbb_720p10s_mpeg2.ts` on fresnel (5.3 MB, MPEG-2 Main, 1280×720@24fps yuv420p, 10s, MPEG-TS container, generated 2026-05-07 23:35 from H.264 master via `ffmpeg -ss 30 -t 10 -vf scale=1280:720 -c:v mpeg2video -profile:v 4 -level:v 8 -b:v 4M -pix_fmt yuv420p`). Provenance + reproducibility: [`phase0_evidence/2026-05-07/test_fixtures.md`](phase0_evidence/2026-05-07/test_fixtures.md).
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- **H.264 reference for regression**: `~/fourier-test/bbb_1080p30_h264.mp4` (725 MB, H.264 High@4.0, 1920×1080@24fps). Reference hashes from T4: HW frame 1 (`+30s`) sha256 `f623d5f7a41697f67dd227275c6f1b21ffc257f65626d32fde8229357f8764c9`, frame 2 sha256 `7d7bc6f2146dda8b2d223bba622c4b9fbe9674181ff1e02afe286b620342e0a8`.
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- **Cross-validator anchor**: ffmpeg-v4l2request MPEG-2 contract from [`phase0_evidence/2026-05-07/cross_validator/mpeg2/`](phase0_evidence/2026-05-07/cross_validator/mpeg2/). 5 `S_EXT_CTRLS` for 2 frames (= 2.5/frame: sequence_header + picture_header + quantisation_matrices, partially batched), 4 `MEDIA_IOC_REQUEST_ALLOC`, 4 `DMA_BUF_IOCTL_SYNC`. Single-threaded `dec0:0:mpeg2vid` worker (no frame-threading for MPEG-2 in ffmpeg). 32 ftrace lines for 2 frames.
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- **Cache-safe verify path**: `mpv --hwdec=vaapi --vo=image` (DMA-BUF + EGL_EXT_image_dma_buf_import + glReadPixels + JPEG encode). Proven equivalent to SW reference on H.264 (T4 — byte-identical at +30s mid-content). Same path applies for MPEG-2 verification.
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### Data that does NOT carry forward (re-acquire if needed)
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- ohm/RK3568 hantro MPEG-2 behaviour. ohm uses RK3568 hantro (`rockchip,rk3568-vpu` kernel variant); fresnel uses RK3399 hantro (`rockchip,rk3399-vpu` variant). Different driver path inside `drivers/media/platform/verisilicon/`. Reference history only — re-verify any contract claim against fresnel.
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- The "MPEG-2 was dropped at iter6 close because A55 CPU handles it fine" disposition. fresnel runs A53 (weaker than ohm's A55), so the disposition for ohm doesn't transfer; HW MPEG-2 decode is potentially valuable on RK3399.
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- Pre-iter6 libva-multiplanar MPEG-2 trace data, if any. Don't have a path to it; if Phase 2 source-read shows the MPEG-2 codepath has been quiet (untested) since iter1, treat MPEG-2 in this fork as a bring-up-from-scratch.
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### Open questions inherited from campaign Phase 0
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- **Cache-stale `vaDeriveImage` bug class on RK3399** (T4 finding). Iter1 must use the DMA-BUF GL import path for pixel verification (per Pass/fail #4 above), not `vaDeriveImage`. The image-export bug fix is Phase 4 cross-cutting work, not iter1-scoped.
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- **`ffmpeg -hwaccel v4l2request` MPEG-2 architectural divergence**: 4 `MEDIA_IOC_REQUEST_ALLOC` (vs our backend's 16 in iter6 binding), `VIDIOC_EXPBUF` + `DMA_BUF_IOCTL_SYNC` for cache-safe readback. Whether to mirror the EXPBUF + SYNC pattern in our backend or stay with the iter6 cap_pool model is a Phase 4 design decision; iter1 doesn't have to converge on ffmpeg's pattern as long as the boolean criteria pass.
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- **HEVC profile enumerated despite `h265.c` not compiled** (T3 finding). Orthogonal to iter1; cleaning up the false-advertising is Phase 4 cross-cutting.
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## Tooling and measurement-instrument inventory (live verification)
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Re-verified on fresnel at iter1 open:
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- `strace -ff -tt -y -e trace=ioctl,openat,close` for libva-side V4L2 ioctl tracing — proven working in T4.
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- `sudo sh -c "echo 1 > /sys/kernel/tracing/events/v4l2/enable"` for kernel v4l2 tracepoints — proven working in T4 + cross-validator sweep.
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- `mpv --hwdec=vaapi --vo=image` (cache-safe pixel verify) — proven on T4, replicates for MPEG-2 in iter1 binding cells.
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- `ffmpeg -hwaccel v4l2request` (independent V4L2 client cross-validator) — proven on all 5 codecs in T6.
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- Backend build harness on fresnel: `ninja -C ~/src/libva-v4l2-request-fourier/build && sudo ninja -C ~/src/libva-v4l2-request-fourier/build install`.
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Iter1 will likely add per-source debug `printf`/`fprintf(stderr, ...)` instrumentation in `src/config.c`'s `RequestCreateConfig` (and possibly `picture.c` MPEG-2 dispatch) to pin the rejection site. That instrumentation is iter1-internal scratch — clean sweep at iter1 close per Phase 5 review precedent (libva-multiplanar iter5 sweep removed ~339 lines of debug instrumentation at close).
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## In-scope (LOCKED 2026-05-07 for iteration 1)
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- libva-v4l2-request-fourier backend MPEG-2 path on hantro-vpu-dec.
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- `src/config.c::RequestCreateConfig` MPEG-2 rejection-site investigation + fix.
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- `src/picture.c` MPEG-2 dispatch path (if Phase 2 source-read finds it implicated).
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- `src/mpeg2.c` set-controls path verification against kernel `hantro_mpeg2.c` and FFmpeg `v4l2_request_mpeg2.c`.
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- iter1 binding-cell test harness: a script that runs the five Pass/fail checks above, captures evidence to `phase0_evidence/<date>/iter1_mpeg2/`, and emits a markdown verdict.
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- Cache-safe pixel verify must use DMA-BUF GL import (not `vaDeriveImage`).
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- Regression check on H.264 (re-run T4 incantation, compare hashes against reference).
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## Out-of-scope (LOCKED 2026-05-07 for iteration 1)
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- HEVC, VP9, VP8 work — separate iterations per the suggested order in `cross_validator_traces.md`.
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- The vaDeriveImage cache-stale bug class fix — Phase 4 cross-cutting work (potentially under a separate iteration).
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- chromium-fourier 149 install on fresnel — not gating; can land as a Phase 0 follow-up to iter1's substrate when convenient.
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- MPEG-2 performance metrics (FPS, CPU%, drops) — Phase 1+ separate iteration. iter1 is boolean correctness only, per the campaign-locked criterion.
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- Long-duration MPEG-2 stress (>10s) — boolean correctness on 2 frames is enough; longer-run regressions surface as a separate iteration if iter1 exposes any.
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- MPEG-2 Simple-only fixtures — the campaign locked fixture is Main profile; Simple is a strict subset and likely passes once Main does.
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- AVI, MPG (program-stream), or other MPEG-2 containers beyond the iter1 fixture's MPEG-TS shape. iter1 fixture is `bbb_720p10s_mpeg2.ts`; container-shape coverage is a Phase 1+ matter.
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- Upstream Linux engagement (per `feedback_no_upstream.md`). Kernel side works; nothing to file.
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## Phase 1 success criterion (LOCKED 2026-05-07)
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Per `feedback_dev_process.md` Phase 1 — define the objective in measurable terms before touching anything. The five Pass/fail bullets at the top of this document are the iter1 success criterion, locked. Phase 3 baseline measurement (the strace + ftrace contract trace of *current* MPEG-2 failure on our backend, plus the reference ffmpeg-v4l2request trace already in `phase0_evidence/2026-05-07/cross_validator/mpeg2/`) feeds Phase 4 plan; Phase 7 verification re-runs all five checks against the patched backend.
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If Phase 3 baseline reveals the chosen criterion is the wrong target (per `feedback_dev_process.md`'s Phase 3 → Phase 1 loopback), the criterion will be rewritten and re-locked. Plausible reasons that would trigger the loopback:
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- The MPEG-2 fixture is malformed in a way that exposes a fixture-side bug rather than a backend-side bug. (Mitigation: ffmpeg-v4l2request decodes the same fixture cleanly per cross_validator data, so this is unlikely.)
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- Pixel verification via DMA-BUF GL import for MPEG-2 produces non-matching hashes for reasons unrelated to the backend (e.g., GL color-space conversion divergence, panfrost MPEG-2-specific quirk). In that case the criterion gets a different verifier — direct ffmpeg `hwdownload,format=nv12` from our libva path, or a custom C reproducer with `msync(MS_SYNC|MS_INVALIDATE)`.
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- The vaCreateConfig rejection site turns out to be in libva itself (not our backend), making "fix RequestCreateConfig" the wrong scope. (Unlikely — the error message threads through our backend's return path.)
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## What "iteration 1 close" looks like
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A clean iter1 close per `feedback_dev_process.md` Phase 8 yields:
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- All five Pass/fail criteria green.
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- A `phase8_iteration1_close.md` document in this campaign repo summarizing the bug, the contract, the fix, and the binding-cell numbers.
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- A second-codec passing entry in the campaign-level scoreboard (currently 1/5, target 2/5 after iter1).
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- Memory entry distilling the lesson — per `feedback_dev_process.md` Phase 8 "do not let the lesson rot in chat history."
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- A debug-instrumentation sweep — any `printf`/`fprintf` added during Phase 6 must be removed before close.
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- The Phase 5 sonnet-architect review pass (per `feedback_dev_process.md` Phase 5) signed off.
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- Commit history under `git.reauktion.de/marfrit/fresnel-fourier` reflecting the iter1 phases, all authored as `claude-noether` per [`memory/feedback_gitea_as_claude_noether.md`](../../.claude/projects/-home-mfritsche-src-fresnel-fourier/memory/feedback_gitea_as_claude_noether.md).
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