A module for splitting timed text into captions
npm install timedtext-vttA module for splitting timed text into captions with intelligent line breaks for better readability.
``bash`
npm install timedtext-vtt
`typescript
import { annotateTokens, type Token } from 'timedtext-vtt';
// Example token array
const tokens: Token[] = [
{
text: "Hello",
start: 0,
duration: 0.5,
metadata: {}
},
{
text: "world!",
start: 0.5,
duration: 0.5,
metadata: {}
}
// ... more tokens
];
// Annotate tokens with metadata for caption splitting
const annotatedTokens = annotateTokens(
tokens,
'en', // Language code for sentence segmentation (e.g. 'en', 'fr', 'es')
37, // Minimum characters per line before attempting a line break
42, // Maximum characters per line before forcing a line break
7, // Maximum duration in seconds for a single caption/cue
2 // Maximum gap in seconds between lines before splitting into separate captions
);
// The annotatedTokens now contain metadata helpful for splitting text
// into captions, including:
// - Line breaks
// - Subtitle breaks
// - Sentence boundaries
// - Punctuation information
// Generate VTT file from annotated tokens
import { generateVTT } from 'timedtext-vtt';
// Group tokens into blocks (e.g., by speaker or paragraph)
const blocks = [annotatedTokens];
// Generate VTT with default settings
const vtt = generateVTT(blocks);
// Or customize the VTT generation
const vtt = generateVTT(blocks,
false, // karaoke: mode with timing for each word
20, // Minimum reading speed in characters per second
5/6 // Minimum duration for each line in seconds
);
// The generated VTT can be used with HTML5 video elements
const video = document.querySelector('video');
const track = document.createElement('track');
track.kind = 'subtitles';
track.label = 'English';
track.srclang = 'en';
track.src = URL.createObjectURL(new Blob([vtt], { type: 'text/vtt' }));
video.appendChild(track);
``
A demo of this module is available at GitHub Pages.