FA-78599 / Broadcast timecode arithmetic / Member archive

Non-drop label to wall clock at pulled-down rates: label to ms rounding · case 04

Elapsed times are a millisecond early for many frames.

Member previewVariant 4 · 3 implementations · 9 checks per implementation

Case contract

Rates "23.976", "29.97", "59.94" run at nominal*1000/1001 frames per second while labels count nominal frames per second (non-drop). mode "to_ms": label to elapsed milliseconds, rounded half up. mode "to_tc": milliseconds to the nearest frame (half up), formatted as a non-drop label wrapping at 24 hours.

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: label to ms rounding	`39580140`	`39580141`	Failed

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