Files
Sylpheed/docs/re/structures
sylph-decoder 311bd16ad8 re: withdraw the eff3 explanation and the flash advice; add a calibration-free
test that refutes 105

Two claims shipped this morning are withdrawn, and the port had already acted
on one of them.

WITHDRAWN 1: "eff3 was never drawn because a 2-unit flash peak is sub-frame."
eff3's alpha is non-zero for t in (58,64), and the capture's frames 133 and 134
sit at t = 60.0 and 62.2 -- squarely inside that window, with eff2 and eff4
both drawn in the same frames. It should have been submitted and was not. The
absence is real and UNEXPLAINED; it is not sampling phase.

WITHDRAWN 2: "a port drawing all five flashes shows more sweep than the
console". No evidence behind it. The port checked against its own renderer and
found it draws them sequentially at their declared times, never more than two
at once -- which is exactly what frames 131-135 show the game doing. The
pile-up worth warning about was the rest() bug, now fixed.

Kept, at the port's request: a frame-by-frame comparison of the build-in WILL
disagree about which flash lands in which frame -- 2 units per submitted frame
against this run's 2.231 units per presented frame -- and neither side is
wrong. Without that stated, the discrepancy reads as a port defect.

Added, and stronger than the argument it replaces: a calibration-free test of
105 vs 120. The glow's draw is omitted when its alpha reaches zero, and the
smallest alpha actually submitted across 807 drawn frames is 1, so the culling
threshold is read off the data rather than assumed. Measured dark fraction
17.7% (173 of 980 settled frames); a 120-unit cycle with its declared 15-unit
hold predicts 14.4%; a 105-unit cycle predicts 2.2%. 105 is out by 8x and
would need a threshold of alpha 11 out of a peak of 80, while the capture
contains submitted draws at alpha 1..12. No frame rate, no pacing factor, no
wall clock.

Also recorded: a regression of five build-in events against their declared
times (residuals <=0.9 frames) recovers t=0 at frame 106.1 when the composite
spike, not in the fit, is frame 107 -- and that same slope makes the glow's
period imply a 114-unit cycle against a declared 120, which is unexplained.
And the vertex-alpha identity holds for the glow but does NOT generalise:
eff4 reads 255/127/254 on consecutive frames.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
2026-08-29 20:03:48 +00:00
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