Subtitle Sync Converter

About the Subtitle Sync converter

Subtitles that are consistently a couple of seconds out are the commonest fault in downloaded caption files, and they are trivially fixable: every timestamp needs the same amount added or subtracted.

Subtitles that start in sync and drift further out as the film goes on are a different problem — that is a frame-rate mismatch, and it needs the timings scaled rather than shifted.

Which problem do you have?

If the subtitles are wrong by the same amount at the start and at the end, you need an offset. Note how far out the first line is, and enter that as the shift — negative if the subtitles appear too late, positive if they appear too early.

If they are correct at the start but progressively worse later, the file was timed for a different frame rate. Pick the matching conversion; the classic case is a PAL transfer, where 23.976 fps content is sped up to 25 fps and subtitles fall behind by about 4% over the runtime.

Finding the right offset

Play the video, note the time the first line is actually spoken, and compare it with the first cue timing shown in the file. The difference is your offset.

Timings are clamped so nothing ends up before zero. A large negative shift will therefore pile the earliest cues at the start of the file rather than discarding them.

Combining both

The frame-rate conversion is applied first and the offset second, so a file that is both stretched and displaced can be corrected in a single pass.

Frequently asked questions