FA-78748 / Broadcast timecode arithmetic / Member archive

Decimal seconds to frame label: rate scaling · case 03

Half-frame offsets are always rounded as if they were whole frames.

Member previewVariant 3 · 3 implementations · 9 checks per implementation

Case contract

Convert a decimal seconds string exactly (no binary floating point) at rate [N,D] to the nearest frame, halves rounding up, and a non-drop label using the nominal rate ceil(N/D). Negative input returns None.

Why this case matters

Timecode arithmetic errors misplace edits, commercial breaks and captions against the broadcast clock.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: rate scaling	`[295, "00:00:12:07"]`	`[296, "00:00:12:08"]`	Failed

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