all files / lib/ midi.js

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var midimessage = require('midimessage')
 
module.exports = function (player) {
  /**
  * Connect a player to a midi input
  *
  * The options accepts:
  *
  * - channel: the channel to listen to. Listen to all channels by default.
  *
  * @param {MIDIInput} input
  * @param {Object} options - (Optional)
  * @return {SamplePlayer} the player
  * @example
  * var piano = player(...)
  * window.navigator.requestMIDIAccess().then(function (midiAccess) {
  *   midiAccess.inputs.forEach(function (midiInput) {
  *     piano.listenToMidi(midiInput)
  *   })
  * })
  */
  player.listenToMidi = function (input, options) {
    var started = {}
    var opts = options || {}
    var gain = opts.gain || function (vel) { return vel / 127 }
 
    input.onmidimessage = function (msg) {
      var mm = msg.messageType ? msg : midimessage(msg)
      if (mm.messageType === 'noteon' && mm.velocity === 0) {
        mm.messageType = 'noteoff'
      }
      if (opts.channel && mm.channel !== opts.channel) return
 
      switch (mm.messageType) {
        case 'noteon':
          started[mm.key] = player.play(mm.key, 0, { gain: gain(mm.velocity) })
          break
        case 'noteoff':
          if (started[mm.key]) {
            started[mm.key].stop()
            delete started[mm.key]
          }
          break
      }
    }
    return player
  }
  return player
}