Web Audio API

README.md

Web Audio API

In here are neat scripts to make the most out of the Web Audio API.

You can paste them into the DevTools.

bass-boost.js

const opts = {
  FREQUENCY: 70,
  SIDECHANNEL_LEVEL: -12,
  POST_GAIN: 2
};
const ctx = new AudioContext();
const audio = document.querySelector('video');
const src = ctx.createMediaElementSource(audio);
const bi = ctx.createBiquadFilter();
const gain = ctx.createGain();

bi.type = 'highshelf';
bi.frequency.setValueAtTime(opts.FREQUENCY, ctx.currentTime);
bi.gain.setValueAtTime(opts.SIDECHANNEL_LEVEL, ctx.currentTime);
gain.gain.setValueAtTime(opts.POST_GAIN, ctx.currentTime);

src.connect(bi);
bi.connect(gain);
gain.connect(ctx.destination);

delay-channel.js

const opts = {
  DELAY: 1
};

const ctx = new AudioContext();
const audio = document.querySelector('video');
const src = ctx.createMediaElementSource(audio);
const splitter = ctx.createChannelSplitter(2);
const merger = ctx.createChannelMerger(2);
const delay = ctx.createDelay(opts.DELAY);

delay.delayTime.setValueAtTime(opts.DELAY, ctx.currentTime);

src.connect(splitter);
splitter.connect(delay, 0);

delay.connect(merger, 0, 0);
splitter.connect(merger, 1, 1);

merger.connect(ctx.destination);

disable-preserve-pitch.js

_=document.querySelector('video');_.mozPreservesPitch=_.preservesPitch=!1

one-channel.js

v = document.querySelector('video');
ctx = new AudioContext();
s = ctx.createChannelSplitter(2);
m = ctx.createChannelMerger(2);
vn = ctx.createMediaElementSource(v);
vn.connect(s)
s.connect(m, 1, 0);
s.connect(m, 1, 1);
m.connect(ctx.destination);

turntable-losing-power.js

FINAL_SPEED = 0.5;
function mapping(time) {
	return (1 - time) * (1 - FINAL_SPEED) + FINAL_SPEED;
}
const makeHandler = fn => ({target}) => {
	target.playbackRate = fn((target.currentTime / target.duration) || 0);
};
globalThis.__handler = makeHandler(mapping);
((vid = document.querySelector('video') ?? document.querySelector('audio')).addEventListener('timeupdate', globalThis.__handler), vid.preservesPitch = false);