How to measure the compression with web audio api?

Question

I would like to create a HTML meter to display the reduction made by the compressor node.

I used this code but it does not change the metter

compressor = context.createDynamicsCompressor();
compressor.threshold = -50;
compressor.ratio = 12;
compressor.attack = 0.003;
compressor.reduction.onchange = function () {
  var gainReduction = pluginSlot1.reduction;
  document.getElementById("meter").value = gainReduction.value;
};

This is connected to this HTML

< meter id="meter" min="0" max="100">

What do I need to do in order for it to work?

Answer 1

Here's a quick and dirty jsbin example: http://jsbin.com/ahocUt/1/edit

Unless there's something I'm missing in the spec, the reduction param doesn't fire any events. You just need to read it on-demand. In my example, that's just happening with a requestAnimationFrame loop.

The other thing you're missing is that you need to set the params with compressor.threshold.value, because compressor.threshold is actually an object.

Hope that helps.