decibri-web

Cross-browser microphone capture for the web.

Zero dependencies.

Meta

---

The decibri platform

Package	Environment	Backend
decibri	Node.js	Native C++ (PortAudio)
decibri-web	Browser	Web Audio API

Same API. Different runtimes. Capture audio anywhere JavaScript runs.

Quick Start

npm install decibri-web

import { Decibri } from 'decibri-web';

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

mic.on('data', (chunk) => {
  // chunk is an Int16Array of PCM samples — ready to use
  console.log(`Received ${chunk.length} samples`);
});

// Must be called from a user gesture (click/tap) in Safari
await mic.start();

// Stop when done
mic.stop();

API Reference

new Decibri(options?)

Creates a new microphone capture instance. Does not start capture — call start().

Option	Type	Default	Description
sampleRate	number	16000	Target sample rate in Hz
channels	number	1	Number of channels (browsers reliably support 1)
framesPerBuffer	number	1600	Frames per chunk (1600 at 16kHz = 100ms)
device	string	system default	deviceId from Decibri.devices()
format	'int16' | 'float32'	'int16'	Sample encoding format
vad	boolean	false	Enable voice activity detection
vadThreshold	number	0.01	RMS energy threshold for speech (0–1)
vadHoldoff	number	300	Ms of silence before 'silence' event
echoCancellation	boolean	true	Browser echo cancellation. Set false for music/tuner apps.
noiseSuppression	boolean	true	Browser noise suppression. Set false for music/tuner apps.
workletUrl	string	(inline)	URL for the AudioWorklet processor. Override if CSP blocks blob: URLs.

Methods

Method	Returns	Description
start()	Promise<void>	Request mic permission and begin capture. No-op if already started.
stop()	void	Stop capture and release all resources. Safe to call anytime.
isOpen	boolean	true while actively capturing.

Static Methods

Method	Returns	Description
Decibri.devices()	Promise<DeviceInfo[]>	List audio input devices. Labels may be empty before permission is granted.
Decibri.version()	VersionInfo	Package version info.

Events

Event	Payload	Description
data	Int16Array or Float32Array	Audio chunk (format depends on format option)
error	Error	Permission denied, worklet load failure, etc.
end	—	Emitted after stop()
close	—	Emitted after stop(), after end
speech	—	VAD: RMS energy crossed threshold (requires vad: true)
silence	—	VAD: sub-threshold audio for vadHoldoff ms (requires vad: true)

Browser Support

Browser	Minimum Version
Chrome	66+
Firefox	76+
Safari	14.1+ (requires user gesture for start())
Edge	79+
iOS Safari	14.5+
Android Chrome	66+

Requires HTTPS (or localhost) for microphone access.

Differences from decibri (Node.js)

Feature	Node.js decibri	decibri-web
Constructor	Sync, capture starts on read	Sync, requires await start()
data payload	Buffer	Int16Array / Float32Array
devices()	Sync	Async (returns Promise)
device option	Number index or name substring	String deviceId only
version()	{ decibri, portaudio }	{ decibriWeb }
echoCancellation	N/A	boolean (default true)
noiseSuppression	N/A	boolean (default true)
backpressure event	Available	Not available
pipe() / streams	Full Readable stream	Not available

WebSocket Streaming Example

import { Decibri } from 'decibri-web';

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);
  }
});

mic.on('error', (err) => console.error(err));

// Start on button click
document.getElementById('start')!.addEventListener('click', () => mic.start());
document.getElementById('stop')!.addEventListener('click', () => mic.stop());

CDN / Script Tag Usage

<script src="https://unpkg.com/decibri-web/dist/index.global.js"></script>
<script>
  const mic = new DecibriWeb.Decibri({ sampleRate: 16000 });
  mic.on('data', (chunk) => console.log(chunk.length, 'samples'));
  document.getElementById('start').onclick = () => mic.start();
</script>

Device Selection

// Call start() first to get permission, then enumerate devices with full 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();

CSP-Restricted Environments

If your Content Security Policy blocks blob: URLs, serve the worklet file yourself:

import { Decibri } from 'decibri-web';

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

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

License

Apache-2.0 — Analytics in Motion