Source: syngen/audio/mixer/auxiliary/reverb.js

  1. /**
  2.  * Provides a auxiliary send for global reverb processing.
  3.  * Because `ConvolverNode`s are quite intensive, implementations are encouraged to leverage this to provide a single global reverb.
  4.  * @augments syngen.utility.pubsub
  5.  * @namespace
  6.  * @see syngen.audio.mixer.send.reverb
  7.  */
  8. syngen.audio.mixer.auxiliary.reverb = (() => {
  9.   const context = syngen.audio.context(),
  10.     delay = context.createDelay(),
  11.     input = context.createGain(),
  12.     output = syngen.audio.mixer.createBus(),
  13.     pubsub = syngen.utility.pubsub.create()
  15.   let active = true,
  16.     convolver = context.createConvolver(),
  17.     highpass,
  18.     lowpass
  20.   convolver.buffer = syngen.audio.buffer.impulse.small()
  21.   delay.delayTime.value = 1/64
  23.   input.connect(delay)
  24.   createFilters()
  25.   convolver.connect(output)
  27.   function createFilters(highpassFrequency = syngen.const.minFrequency, lowpassFrequency = syngen.const.maxFrequency) {
  28.     highpass = context.createBiquadFilter()
  29.     highpass.type = 'highpass'
  30.     highpass.frequency.value = highpassFrequency
  32.     lowpass = context.createBiquadFilter()
  33.     lowpass.type = 'lowpass'
  34.     lowpass.frequency.value = lowpassFrequency
  36.     delay.connect(highpass)
  37.     highpass.connect(lowpass)
  38.     lowpass.connect(convolver)
  39.   }
  41.   function destroyFilters() {
  42.     delay.disconnect()
  43.     lowpass.disconnect()
  44.     lowpass = null
  45.     highpass.disconnect()
  46.     highpass = null
  47.   }
  49.   return syngen.utility.pubsub.decorate({
  50.     /**
  51.      * Creates a `GainNode` that's connected to the reverb input.
  52.      * @memberof syngen.audio.mixer.auxiliary.reverb
  53.      * @returns {GainNode}
  54.      */
  55.     createSend: () => {
  56.       const gain = context.createGain()
  57.       gain.connect(input)
  58.       return gain
  59.     },
  60.     /**
  61.      * Returns whether the processing is active.
  62.      * @memberof syngen.audio.mixer.auxiliary.reverb
  63.      * @returns {Boolean}
  64.      */
  65.     isActive: () => active,
  66.     /**
  67.      * Returns the output node for the send.
  68.      * @deprecated
  69.      * @memberof syngen.audio.mixer.auxiliary.reverb
  70.      * @returns {GainNode}
  71.      */
  72.     output: () => output,
  73.     /**
  74.      * Exposes the parameters associated with reverb processing.
  75.      * @memberof syngen.audio.mixer.auxiliary.reverb
  76.      * @property {AudioParam} delay
  77.      * @property {AudioParam} gain
  78.      * @property {Object} highpass
  79.      * @property {AudioParam} highpass.frequency
  80.      * @property {Object} lowpass
  81.      * @property {AudioParam} lowpass.frequency
  82.      */
  83.     param: {
  84.       delay: delay.delayTime,
  85.       gain: output.gain,
  86.       highpass: {
  87.         frequency: highpass.frequency,
  88.       },
  89.       lowpass: {
  90.         frequency: lowpass.frequency,
  91.       },
  92.     },
  93.     /**
  94.      * Occasionally the filters can enter an unstable or bad state.
  95.      * This provides a solution for replacing them with stable filters.
  96.      * @memberof syngen.audio.mixer.auxiliary.reverb
  97.      * @see syngen.audio.mixer.rebuildFilters
  98.      */
  99.     rebuildFilters: function () {
  100.       const highpassFrequency = highpass.frequency.value,
  101.         lowpassFrequency = lowpass.frequency.value
  103.       destroyFilters()
  104.       createFilters(highpassFrequency, lowpassFrequency)
  106.       this.param.highpass.frequency = highpass.frequency
  107.       this.param.lowpass.frequency = lowpass.frequency
  109.       return this
  110.     },
  111.     /**
  112.      * Sets the active state.
  113.      * Implementations can disable processing for a performance boost.
  114.      * @fires syngen.audio.mixer.auxiliary.reverb#event:activate
  115.      * @fires syngen.audio.mixer.auxiliary.reverb#event:deactivate
  116.      * @memberof syngen.audio.mixer.auxiliary.reverb
  117.      * @param {Boolean} state
  118.      */
  119.     setActive: function (state) {
  120.       if (active == state) {
  121.         return this
  122.       }
  124.       active = Boolean(state)
  126.       if (active) {
  127.         /**
  128.          * Fired whenever the send is activated.
  129.          * @event syngen.audio.mixer.auxiliary.reverb#event:activate
  130.          */
  131.         pubsub.emit('activate')
  132.         input.connect(delay)
  133.       } else {
  134.         /**
  135.          * Fired whenever the send is deactivated.
  136.          * @event syngen.audio.mixer.auxiliary.reverb#event:deactivate
  137.          */
  138.         pubsub.emit('deactivate')
  139.         input.disconnect(delay)
  140.       }
  142.       return this
  143.     },
  144.     /**
  145.      * Sets the impulse buffer for the inner `ConvolverNode`.
  146.      * To prevent pops and clicks, the tail of the previous buffer persists until it fades out.
  147.      * @memberof syngen.audio.mixer.auxiliary.reverb
  148.      * @param {BufferSource} buffer
  149.      */
  150.     setImpulse: function (buffer) {
  151.       input.disconnect()
  153.       convolver = context.createConvolver()
  154.       convolver.buffer = buffer
  155.       convolver.connect(output)
  157.       if (active) {
  158.         input.connect(delay)
  159.       }
  161.       return this
  162.     },
  163.   }, pubsub)
  164. })()