Sync subtitles: shift an SRT, or fix subtitles that drift

First: is it a constant offset or a drift?

• Constant offset: every line is, say, 2 seconds late, from start to finish → shift.
• Drift: fine at the start, a few seconds off at the end → different frame rate (23.976 vs 25 fps, see frame-rate conversion) or a slightly different version → two-point sync.
• Jumps: fine, then suddenly off after a certain scene → a different cut; shift from that line onwards.

Shift all lines

1. Open the SRT (or VTT, ASS, SUB…) in Cuemend.
2. In Timing, type the shift in seconds: 2.5 moves subtitles later, -2.5 earlier. You can also nudge with the ±0.1 s and ±1 s buttons.
3. Choose all subtitles or from subtitle # (to fix only the part after a cut), and press Apply.
4. Check a few lines, then go to Save / convert and save.

Two-point sync (fixes drift)

Find a line near the start and one near the end. In your player, note when each is really spoken (for example 00:01:12,300 and 01:41:05,800). In Cuemend, enter both line numbers and these times under Sync with two points. All other lines are stretched in between, which fixes both offset and speed at once.

Let Cuemend find the offset

If you have the video file, automatic sync listens to the dialogue and finds the offset – and a frame-rate change – by itself.