The blocker on this rung was never the code — it was that `dxva.rs` is the
most safety-critical file in the backend and nothing in it is type-checked
against Windows, so M5's layouts only became trustworthy once a libavcodec
byte capture had verified them field by field. AV1 turns out not to need
that capture: `DXVA_PicParams_AV1` ships in the Windows SDK's OWN `dxva.h`
(10.0.26100.0 and 10.0.28000.0 on .173), which is the declaration the driver
was compiled against and therefore outranks any mirror.
So `layout-probe-av1.c` is committed beside pf-vaadec's probe, compiled with
MSVC against that header on .173, and every number below came out of it:
DXVA_PicParams_AV1 is 912 bytes with alignment 1, PicEntry 36, Tile 16, and
each offset is a compile-time assertion. The nested blocks are asserted
through their own types too, so a wrong internal layout cannot hide behind a
right outer one. Every assertion passed on the first build, which is the
result worth having: the transcription and the compiler agree.
The bit-field words are measured, not assumed. C bit-field allocation order
is ABI-defined rather than standardised, so the probe sets one member at a
time and prints the word, and the tests check each packer against what MSVC
produced — tx_mode at bits 22-23, reference_frame_update at 26, film grain's
sixteen-bit word with matrix_coeff_is_identity at 12, and so on.
Two places AV1 puts things where the other two codecs would not, both now
written down where a conversion will read them:
Global motion is per REFERENCE, inside DXVA_PicEntry_AV1 — where Vulkan
hangs one global-motion block off the picture info. A conversion carrying
the Vulkan shape across would leave every warped reference at identity.
CDEF strengths are packed two-to-a-byte, primary in the low six bits and
secondary in the top two, where both the AV1 syntax and Vulkan's Std block
keep parallel arrays.
A zeroed block names NO reference: 0 is a valid surface index, so a
memset-style default would quietly point every unused reference at surface
0, which decodes, and decodes wrong.
Gates: macOS fmt/clippy/347 tests, container clippy -D warnings over six
crates, 802 tests, workspace check.
enricobuehler
5d1556132e