Getting Started

decibri-web is a browser-based microphone capture library. It uses the Web Audio API and AudioWorklet to capture raw PCM audio chunks in real-time. Same API as decibri for Node.js, different runtime. Zero dependencies, 6.4KB ESM bundle.

Install

Or via CDN:

<script src="https://unpkg.com/decibri-web/dist/index.global.js"></script>

Quick start

Capture microphone audio and log the chunk size:

import { Decibri } from 'decibri-web';

const mic = new Decibri({ sampleRate: 16000 });

mic.on('data', (chunk) => {
  console.log(`Received ${chunk.length} samples`);
});

await mic.start();

start() must be called from a user gesture (click/tap) in Safari. Each chunk contains 100 ms of audio by default (1,600 frames at 16 kHz).

Permission handling

Microphone access requires HTTPS (or localhost). The browser will show a permission prompt when start() is called.

• If the user denies permission, start() rejects with Error('Microphone permission denied')
• The 'error' event also fires with the same error
• Device labels from Decibri.devices() may be empty before permission is granted

Stopping and cleanup

mic.stop();

stop() releases all resources: MediaStream tracks are stopped, AudioContext is closed, all nodes are disconnected, references are nulled. Safe for React/Vue component unmount cycles. Safe to call multiple times or before start().

To restart after stopping:

await mic.start(); // creates a fresh audio pipeline

Device selection

// Start first to trigger permission, then enumerate with labels
await mic.start();
const devices = await Decibri.devices();
console.log(devices);
// [{ deviceId: 'abc123', label: 'Built-in Microphone', groupId: 'g1' }, ...]

// Use a specific device
const usbMic = new Decibri({ device: devices[1].deviceId });
await usbMic.start();

Output formats

// Int16 PCM (default) - ready for most STT engines
const mic = new Decibri({ format: 'int16' });
mic.on('data', (chunk) => {
  // chunk is an Int16Array
});

// Float32 - native browser format, no conversion
const mic2 = new Decibri({ format: 'float32' });
mic2.on('data', (chunk) => {
  // chunk is a Float32Array
});

Voice activity detection

Enable the built-in VAD to receive 'speech' and 'silence' events based on RMS energy thresholding:

const mic = new Decibri({
  sampleRate: 16000,
  vad: true,
  vadThreshold: 0.01,
  vadHoldoff: 300,
});

mic.on('speech', () => console.log('Speaking...'));
mic.on('silence', () => console.log('Silence'));

await mic.start();

WebSocket streaming

const ws = new WebSocket('wss://your-server.com/audio');
const mic = new Decibri({ sampleRate: 16000, format: 'int16' });

mic.on('data', (chunk) => {
  if (ws.readyState === WebSocket.OPEN) {
    ws.send(chunk.buffer);
  }
});

document.getElementById('start').onclick = () => mic.start();
document.getElementById('stop').onclick = () => mic.stop();

Browser support

Requires HTTPS (or localhost) for microphone access.

CSP-restricted environments

By default, decibri-web loads its AudioWorklet processor via an inline Blob URL. If your Content Security Policy blocks blob: URLs:

const mic = new Decibri({
  workletUrl: '/static/decibri-worklet.js',
});

Copy node_modules/decibri-web/dist/worklet.js to your static assets directory and pass the URL.

Next steps