claude-noether
7db15a5685
iter36: remove env-gated DIAG probes (iter29/30/33/35)
...
Cleans up the campaign's exploratory env-gated dumps now that all
bugs are fixed:
- iter29 LIBVA_HEVC_DUMP_SLICE_TAIL (h265.c) — refuted 40-byte inflation theory
- iter30 LIBVA_TS_SCALE (picture.c) — refuted timestamp magnitude theory
- iter33 LIBVA_VP8_DUMP_FRAME (vp8.c) — led to α-30 fix
- iter35 LIBVA_MPEG2_DUMP_FRAME (mpeg2.c) — confirmed MPEG-2 ctrls correct
Total: -131 lines / +7 lines (α-7 comment refresh).
Preexisting framework env knobs retained:
- LIBVA_V4L2_DUMP_OUTPUT (picture.c α-16)
- LIBVA_V4L2_DUMP_CAPTURE (surface.c)
- LIBVA_V4L2_ZERO_CAPTURE (picture.c)
- LIBVA_V4L2_REQUEST_VIDEO_PATH / MEDIA_PATH / NO_AUTODETECT (request.c)
The 3 load-bearing fixes remain unchanged:
α-25 (rkvdec image_fmt pre-seed, src/context.c)
α-29 (slice_params.short_term_ref_pic_set_size, src/h265.c)
α-30 (VP8 OUTPUT header prepend, src/picture.c)
2026-05-14 18:12:55 +00:00
claude-noether
017e27f389
fresnel-fourier iter3 Phase 6 commit B: NEW src/vp8.c + src/vp8.h
...
+ meson.build VP8 entries
Net-new VP8 codec dispatcher implemented against
V4L2_CID_STATELESS_VP8_FRAME (kernel UAPI <linux/v4l2-controls.h>:
1900-1958). Single batched control per frame, no init-time device-
wide menus (VP8 has no DECODE_MODE/START_CODE).
Per-frame submission: ONE VIDIOC_S_EXT_CTRLS, count=1, with full
v4l2_ctrl_vp8_frame struct (1232 bytes — corrected vs Phase 2
implicit ~400 estimate; entropy.coeff_probs[4][8][3][11] alone is
1056 bytes).
vp8_set_controls() implements 10 contract clauses per
phase4_iter3_plan.md:
Clause 1: single-control batched submission (count=1)
Clause 2: stack alloc + memset zero (covers all padding)
Clause 3: width/height/version/per-frame scalars; off-by-one
num_dct_parts = num_of_partitions - 1
Clause 4: DPB timestamp resolution (3 refs: last/golden/alt;
NULL surface → 0-sentinel via memset; mirrors iter1
mpeg2.c::pic.forward_ref_ts)
Clause 5: loop filter (6 fields + 3 flag bits; ADJ_ENABLE/
DELTA_UPDATE/FILTER_TYPE_SIMPLE)
Clause 6: quant base + delta derivation from VAAPI's per-segment
absolute index matrix (subtraction recovers signed
deltas; correct for typical content per Phase 5 S1)
Clause 7: segment fields (segment_probs direct copy; flags
assembled with DELTA_VALUE_MODE set unconditionally
per FFmpeg pattern)
Clause 8: entropy table — 3 VAAPI sources merged (Picture: y_mode +
uv_mode + mv_probs; ProbabilityData: coeff_probs[4][8][3]
[11] direct memcpy; IQMatrix: quant)
Clause 9: coder state + first-partition fields + flags assembly
Clause 10: v4l2_set_controls submission
Phase 5 review amendments incorporated:
C1 first_part_header_bits = slice->macroblock_offset
NOT 0 — kernel hantro_g1_vp8_dec.c:260 + rockchip_vpu2_hw_vp8_
dec.c:372 read this field unconditionally to compute the MB-
data DMA offset. Verified via source identity: vaapi_vp8.c:204
and v4l2_request_vp8.c:83 use byte-identical formulas
(8 * (input - data) - bit_count - 8); VAAPI exposes via
slice->macroblock_offset, V4L2 names it first_part_header_bits.
C2 first_part_size = slice->partition_size[0] +
((macroblock_offset + 7) / 8)
VAAPI's partition_size[0] is the REMAINING bytes after parsing
(vaapi_vp8.c:209; va_dec_vp8.h:193-196). Kernel needs the
TOTAL control partition size; recover by adding back ceil
(macroblock_offset/8) bytes.
Phase 3 keyframe verbatim cross-check: 21923 + 819 = 22742 ✓
C4 (int8_t) cast (NOT (s8); s8 is kernel-internal typedef from
<linux/types.h> not exposed to userspace; userspace UAPI
exposes __s8 with double-underscore; portable userspace cast
is int8_t from <stdint.h>).
S3 assert(probability_set) — kernel hantro_vp8.c::hantro_vp8_
prob_update reads coeff_probs unconditionally; NO default-
table fallback. Practical risk low (FFmpeg vaapi_vp8.c always
sends VAProbabilityBufferType per frame), but assert surfaces
immediately if a future consumer doesn't.
Flags assembly: 6 mainline-documented bits only (KEY_FRAME, SHOW_
FRAME, MB_NO_SKIP_COEFF, SIGN_BIAS_GOLDEN, SIGN_BIAS_ALT). EXP +
bit 0x40 NOT replicated despite ffmpeg-v4l2-request-git setting
them on inter frames — kernel hantro_vp8.c only inspects KEY_FRAME
bit. SHOW_FRAME forced unconditional per Phase 3 Q4 (BBB has no
alt-ref invisible frames; documented fidelity gap).
VAAPI inverts: key_frame=0 means it IS a keyframe per VP8 spec.
Backend writes V4L2_VP8_FRAME_FLAG_KEY_FRAME iff
!picture->pic_fields.bits.key_frame.
After this commit alone: vp8.o compiles standalone; meson.build
links it into the shared library. picture.c can't dispatch yet
(commit C wires that).
Refs:
../fresnel-fourier/phase4_iter3_plan.md (10 contract clauses,
Phase 5 amendments
section)
../fresnel-fourier/phase5_iter3_review.md (C1, C2, C3, C4, S3
all incorporated)
../fresnel-fourier/phase3_iter3_baseline.md (verbatim payload
anchors)
references/ffmpeg-kwiboo/libavcodec/v4l2_request_vp8.c (V4L2 ref)
references/ffmpeg-kwiboo/libavcodec/vaapi_vp8.c (VAAPI source ref)
references/linux-mainline/drivers/media/platform/verisilicon/
hantro_g1_vp8_dec.c (RK3399 kernel driver — first_part_header_
bits + first_part_size usage)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com >
2026-05-08 22:51:12 +00:00
claude-noether