Fansub Subtitle Workflow Hub: Danmaku, ASS, SRT, WebVTT

If the source is a Bilibili XML danmaku export, the first job is converting it into a real subtitle format with collision avoidance. The danmaku XML format is bespoke and not rendered by any standard player. ASS is the right intermediate target because it supports the precise positioning and motion commands needed for scrolling comments. Run the conversion before any other editing.

ASS holds full styling, but most upload targets — YouTube, podcast platforms, generic players — only accept SRT. Convert ASS to SRT for delivery while keeping the original .ass as the editable master. The reverse direction is also useful when a translator hands you an SRT and you need to add styling in Aegisub: convert SRT → ASS to get a real V4+ style block and Dialogue events to work with.

Browsers only read WebVTT inside <track> elements. If you are publishing the same fansub release as both a downloadable SRT and a streamable web preview, you need both files. Going from SRT to VTT mostly means swapping the comma decimals for periods and adding a WEBVTT header. Going the other way strips speaker tags and cue settings that SRT does not understand.

Subtitles authored against a 23.976 fps Blu-ray will drift later and later when played against a 25 fps PAL re-encode. A constant offset only fixes the first cue; you need to rescale every timecode by the FPS ratio. The timing shifter applies both a millisecond offset and an FPS conversion in one pass to avoid double-rounding error. Common presets like 23.976 ↔ 25 and 29.97 ↔ 23.976 cover the most frequent fansub re-sync jobs.

Work in the most expressive format possible, then narrow down at the end. The recommended order is: convert danmaku to ASS first, do all styling and editing in ASS, fix any timing drift while still in ASS (no precision loss), and only convert to SRT or VTT at the very end when you know the final target. Reverse the order and you lose styling information you cannot recover.