Caption timing meaning

A caption job is three clocks that people collapse into one complaint. Transcription is whether the words are right. Timing is whether they arrive with the mouth. Layout is whether they sit in a readable place. 'The captions are off' is usually timing: the line lands late, hangs after the speaker has moved on, or overlaps the next sentence because two cues share a frame.

Word-level timestamps are a finer clock than line-level ones. Karaoke / word-highlight families (Snap, Reveal in Caption Studio) need a timestamp per token so the accent can move with the voice. Ordinary subtitle families need a start and end per line. Both are alignment, not styling. Forced-alignment is the model of that clock: it maps a known transcript onto the audio. Auto captions run speech-to-text and alignment together, which is why a wrong word and a late word look like the same failure until you read the file.

A whole track that is uniformly early or late is an offset: trim an intro and every cue needs to move by the same number of seconds. A track that drifts further out as the video runs is a frame-rate mismatch (a 25 fps caption file against 23.976 fps picture is the usual case) and an offset will make the start right and the end worse. Burned-in captions freeze the clock into pixels; fixing timing after burn-in is a new render, not a nudge.