code: function extractFeatures(chunk) {
      //make it a F32A for efficiency
      var frame = arrayToTyped(chunk);
      //run the extraction of selected features
      var fset = Meyda.extract(featuresToExtract, frame);
      for (let j = 0; j < featuresToExtract.length; j++) {
          var feature = fset[featuresToExtract[j]];
          features[featuresToExtract[j]].push(feature);
      }
    }
docs: helper method to extract features for this chunk