Audio

Class for high-level audio manipulations in javascript. An abstraction from the level of raw data and DSP to the level of natural sound manipulations.

Usage

const Audio = require('audio')

Use-cases

Load ./sample.mp3, trim, normalize, fade in, fade out, save:

Audio.load('./sample.mp3').then(audio =>
  audio
    .trim()
    .normalize()
    .fade(.5)
    .fade(-.5)
    .save('sample-edited.wav')
)

Record 4s of mic input.

navigator.getUserMedia({audio: true}, stream =>

	Audio.record(stream, (err, audio) => {
		audio.save('my-record.wav')
	})
)

Record and download 2 seconds of web-audio experiment

//create web-audio experiment
let ctx = new AudioContext()
let osc = ctx.createOscillator()
osc.type = 'sawtooth'
osc.frequency.value = 440
osc.start()
osc.connect(ctx.destination)

//record 2 seconds of web-audio experiment
let audio = Audio(osc, {duration: 2})
audio.on('end', () => {
	osc.stop()
	audio.download('experiment')
})

Download AudioBuffer returned from offline context

//setup offline context
let offlineCtx = new OfflineAudioContext(2, 44100*40, 44100)
audioNode.connect(offlineCtx)

//process result of offline context
offlineCtx.startRendering().then((audioBuffer) => {
	Audio(audioBuffer).save()
})

Montage audio

let audio = Audio.load('./record.mp3', (err, audio) => {
	//repeat slowed down fragment
	audio.write(audio.copy(2.1, 1).scale(.9), 3.1)

	//delete fragment, fade out
	audio.delete(2.4, 2.6).fadeOut(.3, 2.1)

	//insert other fragment not overwriting the existing data
	Audio('./other-record.mp3', (err, otherAudio) => {
		audio.insert(2.4, otherAudio)
	})

	audio.download('edited-record')
})

Render waveform of HTML5 <audio>

const Waveform = require('gl-waveform')

//create waveform renderer
let wf = Waveform();

//get audio element
let audioEl = document.querySelector('.my-audio')
audioEl.src = './chopin.mp3'

//create audio holder
let audio = new Audio(audioEl)
audio.on('load', (err, audio) => {
	let buf = audio.readRaw(4096)
	let data = buf.getChannelData(0)

	//put left channel data to waveform renderer
	wf.push(data);
})

Process audio with audio-* modules

const Biquad = require('audio-biquad')

let lpf = new Biquad({frequency: 2000, type: 'lowpass'})
let audio = Audio(10).noise().process(lpf)

Data handle - subaudio, for sprites etc

Load intro, append 1s pause, start recording. Once ended, save as file.

Audio(['./intro.mp3', 1, MediaStream]).once('ready', (err, audio) => audio.save(Date() + '-recording.mp3'))

API

1. Core

• new Audio(src?, opts?)
• Audio.from(a, b?, c?, ..., opts?)
• Audio.load(url, opts?, cb?)
• Audio.decode(buf, opts?, cb?)
• audio.buffer
• audio.channels
• audio.duration
• audio.length
• audio.sampleRate
• audio.time(offset)
• audio.offset(time)
• Audio.gain(db)
• Audio.db(gain)
• Audio.isAudio(a)
• Audio.isEqual(a, b, ...c)
• audio.serialize(format)
• audio.save(filename, opts?)
• Audio.record(stream, opts?)
• audio.stream(dst, opts?, onend?)
• audio.clone()

2. Manipulations

• audio.read(dst?, t?, dur?, opts?)
• audio.write(src|val, t?, dur?, opts?)
• audio.insert(data, t?, dur?, opts?)
• audio.slice(t?, dur?, opts?)
• audio.remove(t?, dur?, opts?)
• audio.pad(dur, opts?)
• audio.shift(amt, t?, opts?)
• audio.trim(opts?)
• audio.repeat(times, t?, dur?, opts?)
• audio.reverse(t?, dur?, opts?)
• audio.invert(t?, dur?, opts?)
• audio.gain(db, t?, dur?, opts?)
• audio.fade(t?, dur, opts?)
• audio.normalize(t?, dur?, opts?)
• audio.pan(amt, t?, dur?, opts?)
• audio.mix(audio, t?, dur?, opts?)
• audio.scale(amt, t?, opts?)
• audio.map(fn, opts?)

3. Metrics

• audio.statistics(t?, dur?, opts?)
• audio.bounds(t?, dur?, opts?)
• audio.spectrum(t?, dur, opts?)
• audio.cepstrum(t?, dur)
• audio.loudness(t?, dur)
• audio.memory(t?, dur, opts?)

4. Playback

• audio.play(t?, dur?, opts?)
• audio.pause()
• audio.muted
• audio.loop
• audio.rate
• audio.volume
• audio.paused readonly
• audio.currentTime

See Also

• audiojs − open-source audio components for javascript
• web-audio-api − web-audio-api implementation for nodejs

Related

• tuna

Credits

Acknowledgement to contributors:

• Dmitry Yv for redesign and take on main implementation.
• Jamen Marz for initiative and help with making decisions.
• Daniel Gómez Blasco for patience and work on audio-loader.
• Michael Williams for audio stream insights.

License

MIT © audiojs.