WP1.3, and the measurement that justifies it. `resolve_split_mode`'s 10-bit rule
sat ABOVE the pixel-rate arm and took no codec, so it (D1) vetoed 10-bit 4K120 --
the very case the pixel-rate arm exists for -- and (D2) applied an HEVC-Main10-on-
Ada result to AV1 10-bit, which has no such measurement. Both fixed: the
pixel-rate arm now comes first, and what remains is codec-scoped to HEVC and only
applies BELOW that bar, where a second engine buys nothing anyway.
The rule rested on one datapoint: 5120x1440@240 Main10 on Ada, forced-2 7.6 ms
vs 2.8 ms single-engine -- split 2.7x SLOWER. Dropping the short circuit flips
that exact configuration's behaviour, so it was re-measured on a 4090 (AD102,
driver 610.43.03), 400 Mbps, sub-frame pinned off, via a new mode-parameterizable
Main10 A/B test (PF_AB_MODE=WxHxFPS reproduces the original operating point).
Ada 4090 single forced-2 ratio
3840x2160@60 4483 us 2178 us 2.06x split WINS
5120x1440@240 3689 us 2813 us 1.31x split WINS <- the veto's origin
3840x2160@120 4148 us 2189 us 1.89x split WINS
Blackwell 5070 Ti
3840x2160@60 4216 us 2477 us 1.70x split WINS
5120x1440@240 4651 us 3894 us 1.19x split WINS
Split wins for Main10 at every mode on BOTH architectures, including the config
the veto came from. The original number does not reproduce.
⚠ Caveats, unchanged from the rest of this work: content is trivial (297-300 B/AU
against an 833 KB CBR quota -- zeroed VRAM), so this is the pixel-proportional
term and the bits/frame regime is still unmeasured; debug build; and the driver
differs from whenever the original was taken.
Also validated on Ada in the same session -- the whole spike set reproduces on a
SECOND architecture and an OLDER driver (610.43.03 vs 610.57.04): S1a in-place
split switch accepted with zero IDRs both directions; S1b takes effect
(|C-B|=12 vs |C-A|=1921, the cleanest run yet); S1c pair flip passes; D5 confirmed
(AUTO+sub-frame 4424 vs DISABLE 4409, 15 us apart -- and AUTO without sub-frame
2310 ~= TWO_FORCED 2314, so the arm stays); engines=2 with THREE_FORCED correctly
clamped to mode 2; arbitration converged with exactly 1 keyframe.
Verified: .21 clippy -D warnings clean + 64 unit tests; .133 Windows clippy
-D warnings clean (the resolver signature grew a `codec` param, so both backends
moved); Ada + Blackwell on-hardware as above. fmt clean.
enricobuehler
50b3fd1012