I had parked this as "needs a per-draw capture recording texture base
addresses". It did not. 8AX (1280x720) and ptbase (640x360 at 200%) are
the SAME artwork at two resolutions, which is exactly why comparing
either against a capture is inconclusive -- and why comparing their
DIFFERENCE is not. Compute 8AX - upscale(ptbase), the detail only 8AX
has, and ask whether the capture contains it.
Both candidates are first mapped into the capture's tone domain with the
measured gamma; without that the residual is dominated by the tone
difference and the test is blind.
main menu corr +0.0475 controls +0.0032 shift, -0.0075 flip 68% of ceiling
title corr +0.0634 controls +0.0095 shift, +0.0086 flip 68% of ceiling
Two independent screens, both at 68% of the theoretical ceiling
(sd of the 8AX-only detail over sd of the capture residual), 7-15x their
matched controls. The controls preserve spatial correlation and destroy
only alignment, so they are what "no signal" looks like.
So the recommendation changes: resolve the name and draw 8AX at 1:1.
Upscaling ptbase 2x is wrong, not merely softer. Still do not draw both --
an opaque layer over an identical one costs fill and hides later changes,
and ptbase's element is the one carrying the keyframes, so a consumer
needs its timing with 8AX's pixels.
Also recorded and withdrawn: a cruder pixel-pair test gave 0.00-0.72 for
upscales, 0.98 native and 1.01 for the capture -- apparently decisive.
Additive noise raises both terms of that ratio equally and drives any
value toward 1; fitting a noise term, both "native + noise" and "bilinear
+ noise" reproduce the observed numbers. The conclusion is right, that
test does not establish it, and it is in REFUTED because the number looks
conclusive and is not.
Not shown: whether ptbase is also drawn underneath. 8AX is ~86% opaque
and carries the same art, so it would hide it either way.
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