ffsubsync Subtitle Synchronization Tool
ffsubsync automatically aligns subtitle files to spoken audio by analyzing timing from a reference video or audio file. It is a strong fit for agent workflows that need to repair drifting subtitles without manual waveform editing.
npx skills add agentskillexchange/skills --skill ffsubsync-subtitle-synchronization-tool
ffsubsync is an open-source subtitle synchronization tool built for the very specific job of fixing subtitle timing drift. Instead of asking a human to nudge cues forward and backward in an editor, it uses the soundtrack from a reference media file and aligns subtitle timing automatically. The project supports common subtitle formats such as SRT and can output corrected timing for mismatched rips, fan subtitles, lecture recordings, and downloaded caption files that start too early, too late, or gradually drift over time.
What this skill actually does
The tool works well in agent-driven media pipelines because it has a clean command-line interface and predictable inputs: provide the reference video or audio file, provide the subtitle file, and let ffsubsync estimate the offset and drift. Its documentation also describes speech activity detection and synchronization behavior, which makes it easier to integrate into batch processing workflows. Agents can pair it with FFmpeg for media preparation, run it against subtitle libraries, and then hand the corrected files to downstream muxing, archival, or accessibility steps.
Verification is straightforward. The upstream project lives at smacke/ffsubsync on GitHub, is released on PyPI as ffsubsync, ships under the MIT license, and has public documentation on Read the Docs. The project also shows sustained adoption through substantial GitHub stars and published releases, making it a credible tool to anchor a real ASE skill rather than a speculative idea.