CHAT2VTT – CHAT to WebVTT Subtitle Conversion

Status: Current Last updated: 2026-05-02 03:00 EDT

Purpose

Converts a CHAT file to WebVTT subtitle format for captioned video. WebVTT (.vtt) is the W3C-standard subtitle format used by HTML5 <track> elements; it is closely related to SRT but uses . instead of , as the millisecond separator and includes a WEBVTT header.

Internally, chat2vtt is a thin CLI surface over the same converter crate as chat2srt: both subcommands take a CHAT file with timing bullets and emit numbered subtitle blocks, just in different file formats. The shared infrastructure lives at crates/clan/clan-core/src/converters/chat2srt.rs (chat_to_vtt() for this subcommand, chat_to_srt() for SRT).

Usage

# Write WebVTT to stdout
chatter clan chat2vtt input.cha

# Write to a file
chatter clan chat2vtt input.cha -o input.vtt

Options

The subcommand takes a single positional <PATH> argument (one CHAT file at a time). It does not accept directory inputs, file lists, or the CommonAnalysisArgs filtering flags (--speaker, --gem, etc.) — WebVTT conversion is structural, not analytic.

Input Format

Standard CHAT (.cha) files with timing bullets (•start_end•) on utterances. Utterances without timing bullets are excluded from the output, since WebVTT requires every cue to carry a timestamp.

Output

Numbered subtitle cues with HH:MM:SS.mmm --> HH:MM:SS.mmm timestamps and cleaned text content (no CHAT markers, annotations, or speaker codes). The output begins with the WEBVTT header line that the WebVTT specification requires.

WEBVTT

1
00:00:01.000 --> 00:00:03.500
hello world

2
00:00:04.200 --> 00:00:06.800
how are you

Difference from chat2srt

The two converters share extraction logic and only differ in the output formatting layer:

For the rationale on which utterances are emitted vs skipped, the shape of cleaned text, and what’s intentionally not included from CLAN’s GUI-driven Subtitle Writer flow, see chat2srt. Everything documented there about extraction also applies here; only the serialization differs.

Reference

The CLAN manual section CHAT2SRT covers the original SRT-conversion workflow. WebVTT is an extension on the Rust side; the manual does not document a separate CHAT2VTT binary.