gibberish-dsp/js/filters/filter24.js

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

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

module.exports = function( Gibberish ) {

  Gibberish.genish.filter24 = ( input, _rez, _cutoff, isLowPass, isStereo=false ) => {
    let returnValue,
        polesL = g.data([ 0,0,0,0 ], 1, { meta:true }),
        peekProps = { interp:'none', mode:'simple' },
        rez = g.memo( g.mul( _rez, 5 ) ),
        cutoff = g.memo( g.div( _cutoff, 11025 ) ),
        rezzL = g.clamp( g.mul( polesL[3], rez ) ),
        outputL = g.sub( isStereo ? input[0] : input, rezzL ) 

    polesL[0] = g.add( polesL[0], g.mul( g.add( g.mul(-1, polesL[0] ), outputL   ), cutoff ))
    polesL[1] = g.add( polesL[1], g.mul( g.add( g.mul(-1, polesL[1] ), polesL[0] ), cutoff ))
    polesL[2] = g.add( polesL[2], g.mul( g.add( g.mul(-1, polesL[2] ), polesL[1] ), cutoff ))
    polesL[3] = g.add( polesL[3], g.mul( g.add( g.mul(-1, polesL[3] ), polesL[2] ), cutoff ))
    
    let left = g.switch( isLowPass, polesL[3], g.sub( outputL, polesL[3] ) )

    if( isStereo ) {
      let polesR = g.data([ 0,0,0,0 ], 1, { meta:true }),
          rezzR = g.clamp( g.mul( polesR[3], rez ) ),
          outputR = g.sub( input[1], rezzR )         

      polesR[0] = g.add( polesR[0], g.mul( g.add( g.mul(-1, polesR[0] ), outputR   ), cutoff ))
      polesR[1] = g.add( polesR[1], g.mul( g.add( g.mul(-1, polesR[1] ), polesR[0] ), cutoff ))
      polesR[2] = g.add( polesR[2], g.mul( g.add( g.mul(-1, polesR[2] ), polesR[1] ), cutoff ))
      polesR[3] = g.add( polesR[3], g.mul( g.add( g.mul(-1, polesR[3] ), polesR[2] ), cutoff ))

      let right = g.switch( isLowPass, polesR[3], g.sub( outputR, polesR[3] ) )

      returnValue = [left, right]
    }else{
      returnValue = left
    }

    return returnValue
  }

  let Filter24 = inputProps => {
    let filter24   = Object.create( filter )
    let props    = Object.assign( {}, Filter24.defaults, filter.defaults, inputProps )
    let isStereo = props.input.isStereo 

    const __out = Gibberish.factory(
      filter24, 
      Gibberish.genish.filter24( g.in('input'), g.in('Q'), g.in('cutoff'), g.in('isLowPass'), isStereo ), 
      ['filters','Filter24Classic'],
      props
    )

    return __out
  }


  Filter24.defaults = {
    input:0,
    Q: .25,
    cutoff: 880,
    isLowPass:1
  }

  return Filter24

}