decibri

Cross-platform audio capture, output, and processing for Node.js and browsers.

Installation

npm install decibri

One package for Node.js and browsers. Node.js gets a native addon (Rust via napi-rs). Browsers get a JavaScript AudioWorklet implementation. Platform-specific binaries are installed automatically.

Requires Node.js >= 18. TypeScript definitions are bundled.

Quick Start

Capture audio

const Decibri = require('decibri');

const mic = new Decibri({ sampleRate: 16000, channels: 1 });
mic.on('data', (chunk) => { /* Buffer of Int16 PCM samples */ });
setTimeout(() => mic.stop(), 5000);

Play audio

const { DecibriOutput } = require('decibri');

const speaker = new DecibriOutput({ sampleRate: 16000, channels: 1 });
speaker.write(pcmBuffer);
speaker.end();

Browser capture

import { Decibri } from 'decibri'; // browser entry via conditional export

const mic = new Decibri({ sampleRate: 16000 });
mic.on('data', (chunk) => { /* Int16Array of PCM samples */ });
await mic.start(); // requires user gesture in Safari

Pipe capture to playback (echo)

const mic = new Decibri({ sampleRate: 16000, channels: 1 });
const speaker = new DecibriOutput({ sampleRate: 16000, channels: 1 });
mic.pipe(speaker);

API: Decibri (Capture)

new Decibri(options?)

Creates a Readable stream that captures from the microphone.

Standard ReadableOptions (e.g. highWaterMark) are also accepted.

Methods

Properties

Events

API: DecibriOutput (Playback)

new DecibriOutput(options?)

Creates a Writable stream for speaker playback.

Standard WritableOptions (e.g. highWaterMark) are also accepted.

API: Browser

The browser API uses getUserMedia and AudioWorklet. It differs from the Node.js API because browser audio is fundamentally async.

new Decibri(options?)

Same options as Node.js, plus:

Key differences from Node.js

Voice Activity Detection

Energy mode (default)

Lightweight RMS energy threshold. No model required.

const mic = new Decibri({ vad: true, vadThreshold: 0.01 });
mic.on('speech', () => console.log('speaking'));
mic.on('silence', () => console.log('silent'));

Silero mode

ML-based detection using the Silero VAD v5 ONNX model. More accurate than energy mode, especially in noisy environments.

const mic = new Decibri({ vad: true, vadMode: 'silero', vadThreshold: 0.5 });
mic.on('speech', () => console.log('speaking'));
mic.on('silence', () => console.log('silent'));

The Silero model (~2MB) ships inside the npm package. No downloads or API keys required.

Device Selection

// System default
const mic = new Decibri();

// By name (case-insensitive substring match)
const mic = new Decibri({ device: 'USB' });

// By index
const devices = Decibri.devices();
const mic = new Decibri({ device: devices[1].index });

Decibri.devices();
// [
//   { index: 0, name: 'Microphone', maxInputChannels: 2, defaultSampleRate: 48000, isDefault: true },
//   { index: 1, name: 'USB Headset', maxInputChannels: 1, defaultSampleRate: 44100, isDefault: false }
// ]

Examples

Runnable examples are in examples/.

# Capture to WAV file (no dependencies)
node examples/wav-capture.js

# Stream to WebSocket (requires: npm install ws)
node examples/websocket-server.js   # terminal 1
node examples/websocket-stream.js   # terminal 2

Integration guides for OpenAI, Deepgram, AssemblyAI, and other providers are at decibri.com/docs.

Platform Support

How It Works

decibri is a Rust library using cpal for cross-platform audio I/O. The Rust core compiles to a Node.js native addon via napi-rs and ships pre-built binaries for each platform. Browser support uses a JavaScript AudioWorklet implementation with the same event-driven API.

Audio flows from the OS audio device through cpal's callback, into a crossbeam channel, through frame-exact buffering (guarantees consistent chunk sizes), and into Node.js via a threadsafe function. The JavaScript layer wraps this in a standard Readable stream.

License

Apache-2.0 © decibri