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How to Fix Subtitles That Are Out of Sync
Diagnose constant subtitle offsets, progressive drift, and mismatched cuts, then choose the correct repair.
Identify the type of timing error
Test one subtitle near the beginning and another near the end. The relationship between those two errors tells you which repair is appropriate.
- Same error at both points: constant offset.
- Small error first, larger error later: progressive drift.
- Correct sections separated by sudden jumps: different edit or missing scene.
- Random errors: damaged or poorly authored subtitle.
Repair a constant offset
Measure how early or late the subtitle appears. Add a positive offset when text appears too early; subtract time when it appears too late. Apply the change to every cue, preview the first and last minutes, then export a new file.
Subtitle appears 2.4 seconds early Apply: +2400 ms 00:01:10,000 becomes 00:01:12,400
Repair progressive drift
Progressive drift usually comes from a frame-rate or duration difference. Convert timestamps using the ratio between the subtitle source FPS and video FPS. Common cinema and PAL values are 23.976, 24, and 25 FPS.
New time = old time × source FPS ÷ target FPS 23.976 → 25: multiply timestamps by 0.95904
Know when not to repair
If a director’s cut contains extra scenes or an episode version omits a recap, a global transformation cannot align every cue. Finding a subtitle for the correct cut is faster and more reliable than manually repairing hundreds of discontinuities.
Frequently asked questions
- Should I use plus or minus offset?
- If subtitles appear too early, move them later with a positive offset. If they appear too late, move them earlier with a negative offset.
- Why do subtitles start correctly and become late?
- That pattern usually indicates a duration or frame-rate mismatch rather than a constant delay.
- Does changing subtitle FPS change the video?
- No. It only rescales subtitle timestamps.