What Is Subtitle Synchronization?

Direct definition

Subtitle synchronization is the alignment of each cue’s start and end times with the spoken words (and any required shot changes). Out-of-sync cues appear too early, too late, or drift across the file.

The sections below explain how subtitle synchronization is used in transcription and subtitle work, what people often mix up, and which VideoText workflow applies when the next step is a file or review pass.

Key takeaways

• A constant offset is different from progressive drift.
• Frame-rate mismatches (23.976 vs 24, drop-frame vs non-drop) are a common cause.
• A constant offset is easier to repair than progressive drift across a long file.

How sync is checked

Play the video with the track enabled and sample cues at the beginning, middle, and end. A file that starts aligned and ends several seconds off has drift, not a one-time offset.

Related terms

• timecode
• frame rate
• drop-frame timecode
• SRT file
• All glossary terms

Sources

1. W3C: WebVTT cue timing model