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Automatic subtitle sync to the video’s audio

Instead of guessing the delay, let Cuemend compare the subtitles with where people actually speak in the film. The audio is decoded on your device – a multi-GB MKV is read from disk in slices and never uploaded.

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Steps

  1. Open the subtitle file in Cuemend.
  2. In Auto-sync, choose the video (MKV, MP4, MOV, WebM) or an audio file (M4A, MP3, WAV, MKA). Pick the audio track in the right language if there are several.
  3. Press Find the sync. Cuemend decodes the audio, measures speech-band loudness 100 times a second, and tests every offset within ±10 minutes (adjustable) for normal speed and for the common frame-rate changes.
  4. Read the result and its confidence level. Apply it, then check a few lines in the preview.

Sync to another subtitle instead

If you have well-timed subtitles in another language for exactly this video (for example English subtitles that fit, and Portuguese ones that don’t), choose Sync to another subtitle file. Cuemend matches the on/off pattern of the lines; no audio is needed.

When it can’t work

  • A different cut (extra or missing scenes, ads): no single offset fits. Use two-point sync or shift from a line.
  • Long stretches of music or no dialogue reduce confidence – Cuemend tells you when the result is uncertain.
  • Audio in AC-3, DTS or TrueHD usually cannot be decoded by browsers; choose another audio track or a version with AAC audio.

Questions and answers

How long does it take?

Most of the time is reading the file from disk and decoding the audio: on a normal laptop roughly seconds to a couple of minutes for a feature film, depending on its size and codec.

Is this free?

The analysis is free and shows the offset it found, which you can type into “Shift” yourself. A $7 license applies it in one click, including the speed change, and to many files at once.

Last updated: 2026-10-26