FA-78753 / Broadcast timecode arithmetic / Member archive

Decimal seconds to frame label: nearest frame rounding · case 03

Offsets in the second half of a frame snap back to the earlier frame.

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: nearest frame rounding	`[295, "00:00:12:07"]`	`[296, "00:00:12:08"]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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