gibberish-dsp/js/fx/flanger.js

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

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

module.exports = function( Gibberish ) {
 
let Flanger = inputProps => {
  let props   = Object.assign( { delayLength:44100 }, Flanger.defaults, proto.defaults, inputProps ),
      flanger = Object.create( proto ),
      out

  flanger.__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' ),
          delayLength = props.delayLength,
          feedbackCoeff = g.in( 'feedback' ),
          modAmount = g.in( 'offset' ),
          frequency = g.in( 'frequency' ),
          delayBufferL = g.data( delayLength )

    const writeIdx = g.accum( 1,0, { min:0, max:delayLength, interp:'none', mode:'samples' })
    
    const offset = g.mul( modAmount, 500 )

    const mod = props.mod === undefined ? g.cycle( frequency ) : props.mod
    
    const readIdx = g.wrap( 
      g.add( 
        g.sub( writeIdx, offset ), 
        mod//g.mul( mod, g.sub( offset, 1 ) ) 
      ), 
      0, 
      delayLength
    )

    const leftInput = isStereo ? input[0] : input

    const delayedOutL = g.peek( delayBufferL, readIdx, { interp:'linear', mode:'samples' })
    
    g.poke( delayBufferL, g.add( leftInput, g.mul( delayedOutL, feedbackCoeff ) ), writeIdx )

    const left = g.add( leftInput, delayedOutL )

    if( isStereo === true ) {
      const rightInput = input[1]
      const delayBufferR = g.data( delayLength )
      
      let delayedOutR = g.peek( delayBufferR, readIdx, { interp:'linear', mode:'samples' })

      g.poke( delayBufferR, g.add( rightInput, g.mul( delayedOutR, feedbackCoeff ) ), writeIdx )
      const right = g.add( rightInput, delayedOutR )

      flanger.graph = [ left, right ]

    }else{
      flanger.graph = left
    }
  }

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

  out = Gibberish.factory( 
    flanger,
    flanger.graph, 
    ['fx','flanger'], 
    props 
  ) 

  return out 
}

Flanger.defaults = {
  input:0,
  feedback:.81,
  offset:.125,
  frequency:1
}

return Flanger

}