FA-77918 / Subtitle cue timing / Member archive

Subtitle frame-rate retiming: scale direction · case 03

After a PAL speed-up conversion subtitles drift later and later behind the dialogue.

Member previewVariant 3 · 3 implementations · 9 checks per implementation

Case contract

Cue times authored against a src frame rate are rescaled for playback at dst by t*src/dst, rounded half up to integer ms. Rates are "N", "N/D", or the aliases "23.976"/"29.97" meaning (N+1)*1000/1001. The end is rounded independently; an end that does not exceed the start becomes start+1.

Why this case matters

Subtitle timing defects shift, hide or overlap captions that viewers depend on for comprehension and accessibility.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: scale direction	`[[8, 12], [1200, 5158], [14799, 14803], [0, 121]]`	`[[6, 8], [835, 3589], [10298, 10300], [0, 84]]`	Failed

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