# Subtitle Tools

Edit, validate, synchronize, compare, and convert subtitle files locally in the
browser. Subtitle Tools is an independently versioned application in the
[add·ideas Toolbox](https://git.add-ideas.de/lotobo/toolbox-portal).

## Version 0.2 scope

- Bounded SRT, WebVTT, ASS/SSA and flat-profile TTML/DFXP parsing
- Cue timeline, add/duplicate/split/merge/delete operations, direct
  text/timestamp editing, cue text transforms and configurable diagnostics for
  overlaps, order, duration, reading speed, line count and line length
- Shift and anchor-based stretch operations, negative-time protection,
  source/target frame-rate conversion and frame-grid snapping
- SRT, WebVTT, ASS and safe flat TTML serialization with format-specific preservation where
  possible and a visible cross-format loss warning
- Deterministic index-aligned revision comparison
- Immediate browser-native audio/video playback while cancellable, worker-based
  waveform peak extraction continues; failed or stale jobs retain the last
  valid waveform; the scrollable waveform provides zoom, cue selection,
  previous/next navigation and a live playhead
- UTF-8, UTF-16 LE/BE and ISO-8859-1 file decoding

All source, media and generated output stays in the current browser. The app
makes no external request. Validation is configurable editorial guidance, not a
broadcast, accessibility, or legal compliance certificate. Version 0.2 does not
perform speech recognition, automatic alignment, semantic revision matching, or
pixel-perfect ASS rendering. TTML regions, styling definitions and inherited
timing are not laid out; cue-level references are inspected and export is a
flat, resource-free profile.

## Development

Requires Node.js 22 and npm 11.

```sh
npm ci
npm run check
npm run test:browser
```

## Release

`npm run release:artifact` creates the deterministic
`release/subtitle-tools-0.2.0.zip` and checksum sidecar.

## Licence

GPL-3.0-or-later. Runtime dependencies retain their own licences; see
[THIRD_PARTY_NOTICES.md](THIRD_PARTY_NOTICES.md).