FA-78635 / Broadcast timecode arithmetic / Member archive

Linear timecode BCD field packing: drop detection · case 05

Drop-frame labels are transmitted without the drop-frame flag.

Member previewVariant 5 · 3 implementations · 9 checks per implementation

Case contract

Pack HH:MM:SS:FF into four bytes [frames, seconds, minutes, hours] in transmission order. Each byte holds units in bits 0-3 and tens from bit 4 upward. The frames byte carries the drop-frame flag (bit 6, set when the last separator is ";") and the color-frame flag (bit 7).

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: drop detection	`[153, 9, 0, 25]`	`[217, 9, 0, 25]`	Failed

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