gibberish-dsp/js/fx/vibrato.js

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

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

module.exports = function( Gibberish ) {
 
const Vibrato = inputProps => {
  const props   = Object.assign( {}, Vibrato.defaults, effect.defaults, inputProps ),
        vibrato = Object.create( effect )

  let out
  vibrato.__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 = 44100,
          feedbackCoeff = g.in( 'feedback' ),
          modAmount = g.in( 'amount' ),
          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 readIdx = g.wrap( 
      g.add( 
        g.sub( writeIdx, offset ), 
        g.mul( g.cycle( frequency ), g.sub( offset, 1 ) ) 
      ), 
      0, 
      delayLength
    )

    const leftInput = isStereo ? g.mul( input[0], inputGain ) : g.mul( input, inputGain )

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

    const left = delayedOutL

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

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

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

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

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

Vibrato.defaults = {
  input:0,
  feedback:.01,
  amount:.5,
  frequency:4
}

return Vibrato

}