gibberish-dsp/js/filters/combfilter.js

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

let g = require( 'genish.js' )

let combFilter = function( _input, combLength, damping=.5*.4, feedbackCoeff=.84 ) {
  let lastSample   = g.history(),
  	  readWriteIdx = g.counter( 1,0,combLength ),
      combBuffer   = g.data( combLength ),
	    out          = g.peek( combBuffer, readWriteIdx, { interp:'none', mode:'samples' }),
      storeInput   = g.memo( g.add( g.mul( out, g.sub( 1, damping)), g.mul( lastSample.out, damping ) ) )
      
  lastSample.in( storeInput )
 
  g.poke( combBuffer, g.add( _input, g.mul( storeInput, feedbackCoeff ) ), readWriteIdx )
 
  return out
}

module.exports = combFilter