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subchunk
subchunk/dist/index.js

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Readme

subchunk

Convert ElevenLabs transcript JSON into clean, readable subtitles (.srt / .vtt).

🚨 Problem

ElevenLabs provides SRT exports, but they often look like this:

1
00:00:00,000 --> 00:00:05,000
This is a very long subtitle line that contains too many words and is hard to read quickly.

❌ Issues:

Subtitles are too long
Poor readability
Weak alignment with speech timing
Not optimized for modern content (Reels, Shorts, YouTube)

✅ Solution

ElevenLabs JSON includes word-level timestamps — this tool uses that to generate high-quality subtitles:

✔ Short, readable chunks ✔ Pause-aware timing ✔ Smart sentence splitting ✔ Multi-line subtitles (2 lines max) ✔ Speaker labels (optional) ✔ .srt and .vtt support

✨ Example Output

1
00:00:00,460 --> 00:00:01,160
Three minutes.

2
00:00:01,200 --> 00:00:02,400
That’s all it takes
to get started.

⚙️ Features

🎯 Smart chunking (punctuation + pauses + word limits)
🧠 Human-friendly subtitle splitting
🪶 Lightweight & fast (Bun-powered)
🎬 Presets for different content styles:
- reels (short captions)
- youtube
- podcast
🗣 Speaker labels support
📄 Multiple formats (.srt, .vtt)
🛡 Robust error handling

📦 Installation

Run instantly

bunx subchunk input.json -o output.srt

Install globally

bun install -g subchunk

🚀 Usage

subchunk <input.json> [options]

🔧 Options

Flag	Description	Default
`-o, --output`	Output file	`output.srt`
`--format`	`srt` or `vtt`	`srt`
`--maxWords`	Max words per subtitle	`8`
`--gap`	Pause threshold (seconds)	`0.8`
`--speaker`	Include speaker labels	`false`
`--preset`	`reels`, `youtube`, `podcast`	—

🎯 Presets

Preset	Use Case	Behavior
`reels`	Shorts / TikTok	Very short captions
`youtube`	General videos	Balanced
`podcast`	Long conversations	Longer subtitles

Example:

subchunk input.json --preset reels

📄 Input Format (ElevenLabs JSON)

{
  "segments": [
    {
      "text": "Three minutes.",
      "words": [
        {
          "text": "Three",
          "start": 0.46,
          "end": 0.66,
          "type": "word"
        }
      ]
    }
  ]
}

🧠 How It Works

Extracts words from segments[].words[]
Detects:
- sentence endings (. ? !)
- pauses in speech
- word limits
Groups words into natural subtitle chunks
Formats into .srt or .vtt

🧪 Examples

# basic
subchunk input.json

# reels (short captions)
subchunk input.json --preset reels

# include speaker labels
subchunk input.json --speaker

# VTT format
subchunk input.json --format vtt

# custom tuning
subchunk input.json --maxWords 6 --gap 0.5

🎯 Why This Matters

Good subtitles are critical for:

Viewer retention 📈
Accessibility ♿
Mobile-first content 📱

This tool helps you generate modern, readable captions instead of outdated long blocks.

📄 License

MIT