Files
Sylpheed/docs/re/structures
sylph-decoder cf91ad1dcc re: the forced-backdrop span -- 256 vs 211 is a bundle mismatch, and the hold
decides 55% of verdicts

The port implemented the forced-backdrop rule and reported a discrepancy:
palogo_eff0.prm at 256 opaque instants against this corpus's 211.

There is no discrepancy. palogo_eff0.prm appears on BOTH splashes -- the
publisher (entries 10, 13) runs to t=255, giving 256 instants; the developer
(11, 14) runs to t=210, giving 211. Same definition, different bundle. The page
now names the entries so it cannot recur.

The definition, stated: the span is 0..=max keyframe time over every element in
the build, and an element HOLDS its final pose past its own last keyframe --
which is what pose_at does, and which is decoded rather than assumed (a group
holds at its last keyframe rather than looping; the declared +0x08 never falls
short of the last keyframe, the slack being that hold).

The port's instinct that the hold was load-bearing was right. Over the 130
keyless full-screen primitives with an opaque interval:

  * span = the header's declared +0x08          ->  0 verdicts change
  * span = the primitive's own last keyframe    -> 72 change
  * elements GONE after their last keyframe     -> 72 change

So the hold decides 55% of verdicts -- and dropping it is REFUTED by a measured
order. palogo_eff0.prm is a single keyframe at t=0: without the hold it is
opaque for one instant, no other element is up yet, and the rule calls it free,
against a game measured painting it first. Pinned by a new test that spells out
the counterfactual rather than importing it.

The verdicts that matter are convention-independent: pgloading_eff00.prm is
FIRST under all four conventions and pteff00.prm FREE under all four. And the
header length is interchangeable with the elements' maximum -- zero
disagreements disc-wide.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
2026-08-29 21:14:58 +00:00
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