volume.js

player.onPostProcessing = function(buffer, channelCount) {
  if (!player.playing) return;

  var volume = DGPlayer.volume / 100;
  for (var i = 0; i < buffer.length; i++) {
    buffer[i] *= volume;
  }
};

var filter = new VolumeFilter();
player.onPostProcessing = function(buffer) {
  filter.value = DGPlayer.volume;
  filter.process(buffer);
};