gibberish-dsp/js/fx/bitCrusher.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 BitCrusher = inputProps => {
  const  props = Object.assign( { bitCrusherLength: 44100 }, BitCrusher.defaults, effect.defaults, inputProps ),
         bitCrusher = Object.create( effect )

  let out

  bitCrusher.__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
    }

    let input = g.in( 'input' ),
        inputGain = g.in( 'inputGain' ),
        bitDepth = g.in( 'bitDepth' ),
        sampleRate = g.in( 'sampleRate' ),
        leftInput = isStereo ? input[ 0 ] : input,
        rightInput = isStereo ? input[ 1 ] : null
    
    let storeL = g.history(0)
    let sampleReduxCounter = g.counter( sampleRate, 0, 1 )

    let bitMult = g.pow( g.mul( bitDepth, 16 ), 2 )
    let crushedL = g.div( g.floor( g.mul( g.mul( leftInput, inputGain ), bitMult ) ), bitMult )

    let outL = g.switch(
      sampleReduxCounter.wrap,
      crushedL,
      storeL.out
    )

    if( isStereo ) {
      let storeR = g.history(0)
      let crushedR = g.div( g.floor( g.mul( g.mul( rightInput, inputGain ), bitMult ) ), bitMult )

      let outR = g.switch( 
        sampleReduxCounter.wrap,
        crushedR,
        storeL.out
      )

      bitCrusher.graph = [ outL, outR ]
    }else{
      bitCrusher.graph = outL
    }
  }

  bitCrusher.__createGraph()
  bitCrusher.__requiresRecompilation = [ 'input' ]

  out = Gibberish.factory( 
    bitCrusher,
    bitCrusher.graph,
    ['fx','bitCrusher'], 
    props 
  )
  return out 
}

BitCrusher.defaults = {
  input:0,
  bitDepth:.5,
  sampleRate: .5
}

return BitCrusher

}