A delay is not the same as drift.

Measure at both ends

Choose a clear spoken phrase near the beginning and another near the end. Compare the start of each phrase in the subtitle file with the moment it is spoken in the video. Use the same convention at both points: the beginning of the same word, rather than the end of one sentence and the start of another.

If both captions are late by roughly the same amount, use a constant shift. If the gap grows over time, a two-point correction may fit better. A subtitle file from a different edit can contain jumps that neither method can fix globally.

Apply a constant shift

The offset is added to every start and end time. Positive numbers show captions later; negative numbers show them earlier. If a caption starts at 12.000 seconds and the matching speech starts at 10.500 seconds, enter −1500 milliseconds. Its duration is unchanged.

Arbray rejects a change that would put a cue before zero. It does not silently cut the beginning of the file. You can instead edit that cue or choose a smaller shift. Undo returns the complete file to the previous state.

new time = old time + offset
12,000 ms + (−1,500 ms) = 10,500 ms

Correct a steady drift with two points

Enter two times from the subtitles and the corresponding times in the video. Arbray fits a straight-line mapping through those pairs and applies it to cue starts and ends. The second time must be later than the first in both columns. Use widely separated anchors for a useful measurement.

For example, subtitle times 10 and 110 seconds might match video times 12 and 114 seconds. The scale is 102 ÷ 100 = 1.02, so a subtitle at 60 seconds moves to 63 seconds. Durations scale too. Millisecond rounding can matter for very short cues; run the review again.

scale = (video 2 − video 1) / (subtitle 2 − subtitle 1)
new time = video 1 + (old time − subtitle 1) × scale

Know when to stop shifting

Check a middle scene after any global correction. If it is still out of sync while the anchors match, look for removed scenes, an inserted introduction or a different cut. Edit affected cues or use a full video editor for segment-level timing. Arbray does not automatically align speech and cannot discover scene cuts from a subtitle file alone.