FA-78829 / Broadcast timecode arithmetic / Member archive

90 kHz presentation timestamp to frame label: elapsed wrap · case 04

Frames after a PTS rollover get negative frame numbers.

Member previewVariant 4 · 3 implementations · 9 checks per implementation

Case contract

PTS values are 33-bit 90 kHz ticks. The elapsed ticks since first_pts wrap modulo 2^33, except that a PTS less than 90000 ticks before first_pts (reordering pre-roll) returns None. The frame is the nearest frame at rate [N,D] (halves up); the label uses nominal rate ceil(N/D) and wraps 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: elapsed wrap	`[-216832, "21:29:25:08"]`	`[2071528, "23:58:33:16"]`	Failed

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

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