 claude-noether
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fd3fce86a6
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iter3 Phase 3: baselines — VP8 cross-validator + 3-codec regression
+ SW reference
Captured on fresnel 2026-05-08 across two suspend cycles (laptop
dropped twice mid-run, captures preserved on /tmp/iter3_phase3).
All Phase 3 deliverables green.
Substrate verification:
backend SHA256: 9e27...6258 (matches iter2 close)
3-codec regression block: ALL 6 reference hashes match byte-for-
byte vs iter1+iter2 (H.264 +30s, MPEG-2 +02s, HEVC +02s on rkvdec/
hantro). Substrate has not regressed; criterion-5 anchor solid.
Cross-validator anchor (ffmpeg-v4l2request VP8 strace):
- VIDIOC_S_EXT_CTRLS, count=1, ctrl_class=V4L2_CTRL_CLASS_CODEC_
STATELESS, id=0xa409c8, size=1232 bytes
- struct size CORRECTED: v4l2_ctrl_vp8_frame = 1232 bytes (NOT
400 as one might assume; entropy.coeff_probs[4][8][3][11] alone
is 1056 bytes)
- keyframe (frame 1) verbatim payload captured: y_ac_qi=8,
last/golden/alt ts all 0, flags=0x0d (KEY|SHOW|NOSKIP),
y_mode_probs=[145,156,163,128] (matches FFmpeg keyframe const)
- inter frame verbatim payload captured: y_ac_qi=122, all DPB
timestamps non-zero, flags=0x66 (anomaly: bit 0x40 not in
mainline UAPI; vendor-patched ffmpeg-v4l2-request-git;
kernel hantro_vp8.c only inspects KEY_FRAME bit, ignores
bit 0x40)
VP8 SW pixel-verify reference (criterion-4 anchor):
vp8_sw_001.jpg: e43757a40e5d71ad176455c0fda14c2cbf9351b702188fc8ad
584d789db2c984
vp8_sw_002.jpg: a86bf885e588257731ff6cf8d2ccc5756be550e85220eee1c3
e6ea8c0c78e97a
Frame 1 != Frame 2 (real motion). These are the Phase 7 byte-
compare HW-vs-SW targets.
Open-question resolution (5 of 6 answered empirically):
Q1 first_part_header_bits — varies per frame (key=6550, inter
ranges 86..254); VAAPI doesn't expose. Phase 4 fallback:
leave 0 and check kernel behavior at Phase 7 byte-compare.
Phase 5 review will flag as known fidelity gap.
Q2 num_dct_parts vs VAAPI num_of_partitions — confirmed off-by-
one: kernel = VAAPI - 1 (BBB has VAAPI=2, kernel=1).
Q3 DPB timestamp 0-sentinel — confirmed: keyframe writes all
three timestamps as 0; iter3 mirrors iter1 mpeg2.c pattern.
Q4 SHOW_FRAME default — set on every captured frame (BBB has no
alt-ref invisible). Force unconditional in libva backend.
Q5 lf.flags FILTER_TYPE_SIMPLE — not set; BBB normal loop filter.
Direct mapping from VAAPI filter_type=0.
Q6 First-frame DPB sentinel — confirmed Q3; no self-reference
fallback needed (different from iter1 mpeg2.c).
V4L2 binding cells this boot:
rkvdec : /dev/video3 + /dev/media1
hantro-vpu-dec: /dev/video5 + /dev/media2
Capture artefacts on fresnel /tmp/iter3_phase3/ preserved for
Phase 7 re-run:
vp8_strace.* (19 files, multi-thread)
decode_vp8.py (payload decoder)
vp8_sw_00{1,2}.jpg (criterion-4)
{h264,mpeg2,hevc}_hw_00{1,2}.jpg (criterion-5)
Refs:
phase0_findings_iter3.md (Phase 1 lock)
phase2_iter3_situation.md (Phase 2 contract surface)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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2026-05-08 20:14:46 +00:00 |
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