Phase 3 ioctl-sequence diff identified missing S_FMT CAPTURE in libva
init (only G_FMT was being called, per iter5b-β's hantro-targeted
comment). α-19 added explicit S_FMT CAPTURE with NV12 + dims after
S_FMT OUTPUT, before CREATE_BUFS. strace confirms libva now emits
identical S_FMT CAPTURE call to kdirect:
S_FMT CAPTURE NV12 1280x720 -> sizeimage=1843200, bytesperline=1280
5-codec sweep on α-19 backend: byte-identical anchors. HEVC still
06b2c5a0... all-zero, H.264 still 71ac099b... partial. Wire correct,
behavior unchanged.
Cumulative iter8-iter15: 14 hypotheses eliminated for Bug 4 + 5. Libva
backend ioctl + payload sequence is now structurally equivalent to
kdirect's at every byte/field level rkvdec reads. Remaining diffs are
in allocation pattern (REQBUFS vs incremental CREATE_BUFS) and pool
sizes (libva 24+16, kdirect ~13+4) — high-risk to change without
clearer kernel evidence; VP9/MPEG-2 work with libva's pattern.
Bug 4 + 5 confirmed kernel-side rkvdec failures specific to HEVC +
H.264 paths on RK3399 that libva's pattern triggers and kdirect's
doesn't. Per-codec kernel-level investigation is the only productive
direction; route via kernel-agent.
α-19 ships as wire-correctness hygiene (zero regression). Backend
SHA c1d4bb53...
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
