node-web-audio-api

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

Install

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

Example

const { AudioContext, OscillatorNode, GainNode } = require('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);
}, 50);

or using with EcmaScript module syntax

import wabaudioapi from 'node-web-audio-api';
const { AudioContext, OscillatorNode, GainNode } = webaudioapi;

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 https://github.com/orottier/web-audio-api-rs/issues/216
• On Linux systems, the audio backend is Alsa, 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 you should provide a latency hint when building an audio context:

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

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

Supported Platforms

Manual Build

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

1. Install rust toolchain

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

2. 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.