gibberish-dsp/js/fx/delay.js

Gibberish is designed to be an optimized API for audio synthesis using per-sample techniques.

let g = require( 'genish.js' ),
    effect = require( './effect.js' )

module.exports = function( Gibberish ) {
 
let Delay = inputProps => {
  let props = Object.assign( { delayLength: 88200 }, effect.defaults, Delay.defaults, inputProps ),
      delay = Object.create( effect )

  let out
  delay.__createGraph = function() {
    let isStereo = false
    if( out === undefined ) {
      isStereo = typeof props.input.isStereo !== 'undefined' ? props.input.isStereo : false 
    }else{
      isStereo = out.input.isStereo
      out.isStereo = isStereo
    }    

    const input      = g.in( 'input' ),
          inputGain  = g.in( 'inputGain' ),
          delayTime  = g.in( 'time' ),
          wetdry     = g.in( 'wetdry' ),
          leftInput  = isStereo ? g.mul( input[ 0 ], inputGain ) : g.mul( input, inputGain ),
          rightInput = isStereo ? g.mul( input[ 1 ], inputGain ) : null
      
    const feedback = g.in( 'feedback' )

    // left channel
    const feedbackHistoryL = g.history()
    const echoL = g.delay( g.add( leftInput, g.mul( feedbackHistoryL.out, feedback ) ), delayTime, { size:props.delayLength })
    feedbackHistoryL.in( echoL )
    const left = g.mix( leftInput, echoL, wetdry )

    if( isStereo ) {
      // right channel
      const feedbackHistoryR = g.history()
      const echoR = g.delay( g.add( rightInput, g.mul( feedbackHistoryR.out, feedback ) ), delayTime, { size:props.delayLength })
      feedbackHistoryR.in( echoR )
      const right = g.mix( rightInput, echoR, wetdry )

      delay.graph = [ left, right ]
    }else{
      delay.graph = left 
    }
  }

  delay.__createGraph()
  delay.__requiresRecompilation = [ 'input' ]
  
  out = Gibberish.factory( 
    delay,
    delay.graph, 
    ['fx','delay'], 
    props 
  )

  return out
}

Delay.defaults = {
  input:0,
  feedback:.5,
  time: 11025,
  wetdry: .5
}

return Delay

}