Overtone Captions
Word-timed captions for web developers and video creators
Developer ToolsOpen sourceOpen source · verified#captions#video#cli
Listed by the ProductPerch team from Hacker News · not launched here yet
What is Overtone Captions?
Overtone is an open source caption format and toolset that generates word-timed subtitles from audio or video files. It stores each spoken word with its exact timestamp and speaker information in a single .overtone.json file. Instead of creating separate subtitle files for different devices, it keeps all the data in one place so players can dynamically adjust the layout.
The project includes a command line interface that works offline with Node.js or connects to speech APIs like OpenAI and Azure. Users can recut existing SRT files or transcribe new audio directly. The system applies readability rules during formatting, such as keeping names and numbers intact, separating speakers onto different lines, and using natural pauses to break captions.
A video.js plugin displays the captions by automatically selecting the correct layout for the current player dimensions. This solves the common problem where standard captions look too wide on phones or split awkwardly across lines. The repository provides documentation, examples, and a benchmark to help developers integrate the format into their video workflows.
Overtone Captions features
- Single file format stores words, timestamps, and speaker data
- CLI generates captions from audio, video, or existing subtitles
- Automatically cuts layouts for 16:9, 9:16, or custom aspect ratios
- video.js plugin adapts caption display to player dimensions
- Offline transcription support using whisper.cpp and Ollama
- Applies readability rules to keep names and numbers together
Who uses Overtone Captions and for what
- Convert vertical social media videos to horizontal formats without losing caption readability
- Embed responsive subtitles in web applications using the video.js player
- Generate accurate word-timed captions directly from podcast audio or meeting recordings
- Update existing SRT subtitle files to work properly on mobile screens
- Ensure consistent speaker separation and pause-based line breaks for accessibility
Overtone Captions FAQ
Is Overtone Captions free?
Yes, the repository lists an MIT license, which means the software is free to use and modify. The website does not mention commercial pricing or enterprise plans.
Does Overtone Captions require an internet connection?
The CLI can run completely offline using Node.js and local models like whisper.cpp and Ollama. Cloud transcription requires API keys for OpenAI or Azure, but the tool itself does not mandate an online connection.
What platforms does Overtone Captions support?
The command line tool runs on any operating system that supports Node.js 22.12 or newer. The video.js plugin works in standard web browsers. The website does not specify native mobile or desktop app support.
How does Overtone differ from standard WebVTT or SRT files?
Standard formats store finished caption lines that cannot be easily resized. Overtone stores individual words and timestamps, allowing the player to dynamically rewrap and cut the text for different screen shapes.
Can I use Overtone Captions with my own video player?
Yes, the core format is a standard JSON file that can be parsed by any codebase. A dedicated video.js plugin is provided for easy integration, but the underlying data structure is platform agnostic.
Comments (0)
Comments and upvotes open when this product launches on ProductPerch.
More Developer Tools launches
Feel iOS haptic patterns on a real iPhone, copy the code
Deploy anywhere from your AI tool.
Free product launch platform for indie makers
Akii: SEO & AI Search OptimizerOpen source · verified
Free SEO, AEO and GEO tools for Claude Code.
Compare hosting, VPS, and domain prices side by side
Monitor Laravel scheduled tasks and queues
