`node-web-audio-api`

Nodejs bindings for orottier/web-audio-api-rs using napi-rs

Install

npm install [--save] node-web-audio-api

Example

import { AudioContext, OscillatorNode, GainNode } from 'node-web-audio-api';

const audioContext = new AudioContext();

setInterval(() => {
  const now = audioContext.currentTime;

  const env = new GainNode(audioContext);
  env.connect(audioContext.destination);
  env.gain.value = 0;
  env.gain.setValueAtTime(0, now);
  env.gain.linearRampToValueAtTime(1, now + 0.02);
  env.gain.exponentialRampToValueAtTime(0.0001, now + 1);

  const osc = new OscillatorNode(audioContext);
  osc.frequency.value = 200 + Math.random() * 2800;
  osc.connect(env);
  osc.start(now);
  osc.stop(now + 1);
}, 80);

or using with old fashionned commonjs syntax

const { AudioContext, OscillatorNode, GainNode } = require('node-web-audio-api');

const audioContext = new AudioContext();
//...

Caveats

Currently the library does not provide any way of chosing the output interface, system default interface will be used. As the spec and web-audio-api evolve evolve, thus should change in the future see orottier/web-audio-api-rs#216
On Linux systems, the audio backend is Alsa, which limits the number of online AudioContext to 1. This is subject to change in the future.

Raspberry Pi

On Raspberry Pi, the default render quantum size (128) is too small and underruns occurs frequently. To prevent that, if you do not explicitely provide a latency hint in the AudioContext options, the value is automatically set to 'playback' which uses a buffer of 1024 samples. While this is not per se spec compliant, it allow usage of the library in a more user friendly manner. In the future, this might change according to the support of other audio backend, which is now alsa.

const audioContext = new AudioContext({ latencyHint: 'playback' });

The 'playback' latency hint, 1024 samples / ~21ms at 48000Hz, has been found a good value.

Supported Platforms

	binaries	tested
Windows x64	✓
Windows arm64	✓
macOS x64	✓	✓
macOS aarch64	✓
Linux x64 gnu	✓
Linux arm gnueabihf (RPi)	✓	✓

Manual Build

If prebuilt binaries are not shippped for your platform, you will need to:

Install rust toolchain

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Install and build from github

npm install --save git+https://github.com/b-ma/node-web-audio-api.git
cd node_modules/node-web-audio-api
npm run build

The package will then be built on your machine, which might take some time

Known limitation / caveats

async function are not trully async but only monkey patched on the JS side, this will be updated once web-audio-api-rs provide async version of the methods.
see web-audio-api-rs

Development notes

The npm script rely on cargo-bump to maintain version synced between the package.json and the Cargo.toml files. Therefore, you will need to install cargo-bump on your machine

cargo install cargo-bump

License

This project is licensed under the BSD-3-Clause license.

bthj/node-web-audio-api

node-web-audio-api