beat-emitter's Introduction

beat-emitter

WebAudio scheduler with an event emitter

Features

runs as a web worker (so that setInterval fires more reliably)
schedules audio events with a slight look-ahead, for precise timing

Usage

const beatEmitter = require('beat-emitter')

const ac = new AudioContext()
const beats = beatEmitter(ac)

beats.setBpm(110)

// optional: shuffle factor (best results between .02 and .09)
beats.setShuffle(.07)

beats.start()
beats.schedule((beat, time) => {
  // play a note every 2nd beat
  if (beat % 2 === 0) {
    const osc = ac.createOscillator()
    osc.frequency.value = 440
    osc.start(time)
    osc.stop(time + 0.1)
    osc.connect(ac.destination)
  }
})

Acknowledgements

I learned a lot from reading https://github.com/cwilso/metronome and based the code on this.

beat-emitter's People

Contributors

Stargazers

Watchers

beat-emitter's Issues

worker function has a problem

If user call start function twice in a row, the user won't be able to stop it anymore.

Below codes can fix it. Which one is your preference?

function worker () {
  let timerId = null

  self.onmessage = function (e) {
    if (timerId === null && e.data === 'start') {
      timerId = setInterval(postMessage.bind(null, 'tick'), 25)
    } else if (e.data === 'stop') {
      clearInterval(timerId)
      timerId = null
    }
  }
}

function worker () {
  let timerId

  self.onmessage = function (e) {
    clearInterval(timerId)
    timerId = null
    if (e.data === 'start') {
      timerId = setInterval(postMessage.bind(null, 'tick'), 25)
    }
  }
}

Recommend Projects