Review by sonnet-architect with cold-context source reads of fork +
kernel UAPI + VAAPI + FFmpeg references + kernel rkvdec source.
Reviewer applied Direction 2 (empirical-over-theoretical) by
test-compiling struct sizes, gcc-c-checking VAAPI field accesses,
and source-tracing FFmpeg's filter-mode XOR provenance.
Critical findings (all empirically validated by author before
incorporation per feedback_review_empirical_over_theoretical.md):
C1 - interpolation_filter double-XOR: vaapi_vp9.c:62 ALREADY applies
`filtermode ^ (filtermode <= 1)` when filling VAAPI's
mcomp_filter_type. Plan's second XOR was incorrect; would swap
EIGHTTAP and EIGHTTAP_SMOOTH for inter frames -> wrong
loop-filter strength. Fix: direct assignment, no XOR.
C2 - LF deltas not persistent: kernel UAPI explicitly says
"users should pass its last value" when delta_update=0. Plan
memset-zeroed each frame; would send {0,0,0,0,0,0} on BBB inter
frames instead of {1,0,-1,-1,0,0}. Fix: add persistent vp9_lf
state to object_context, init to VP9 spec defaults, update only
when parser sees delta_update=1, always copy to kernel control.
C3 - reference_mode out-parameter missing: reference_mode lives in
FRAME struct, not COMPRESSED_HDR. Plan referenced
`compressed_hdr_reference_mode` placeholder which would be an
undefined identifier -> compile failure. Fix: add
`uint8_t *out_reference_mode` param to vp9_fill_compressed_hdr;
derive `allowcompinter` at call site from the 3 sign biases.
C4 - Mitigation B scope claim overstated: walk-and-pick-first always
selects rkvdec on 7.0 (since video1 enumerates first). Hantro
codecs (MPEG-2, VP8) at video3 still require env override.
Fix: qualify criterion-5 trace; add LIBVA_V4L2_REQUEST_NO_
AUTODETECT=1 escape hatch for legacy callers.
6 Suggested (S1-S6): all confirm plan correctness OR are scope-
aligned non-issues. S4 (uv_mode memcpy omission safe for rkvdec)
baked into Clause 9 amended text.
Without this review, iter4 Phase 6 would have failed first compile
(C3) + produced wrong inter-frame output (C1+C2) + caused user
confusion (C4). Estimated saving: 1 compile failure + 1 Phase 7 ->
Phase 4 loopback + 1 doc correction.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
marfrit