go-broadcast/soundmeter.html at master · tryphon/go-broadcast · GitHub

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<!DOCTYPE html>
<meta charset="utf-8">
<body>

<style>
.channel {
  width: 0px;
  height: 20px;
  background: green;
}

#soundmeter {
  width: 200px;
  border: 1px solid black;
}
</style>

<div id="soundmeter">
  <div id="soundmeter_channel0" class="channel">
  </div>
  <div id="soundmeter_channel1" class="channel">
  </div>
  <div id="soundmeter_channel2" class="channel">
  </div>
  <div id="soundmeter_channel3" class="channel">
  </div>
</div>

<script>
  if (!Array.prototype.map) {
    Array.prototype.map = function(fun /*, thisp*/) {
      var len = this.length;
      if (typeof fun != "function")
        throw new TypeError();

      var res = new Array(len);
      var thisp = arguments[1];
      for (var i = 0; i < len; i++) {
        if (i in this)
          res[i] = fun.call(thisp, this[i], i, this);
      }
      return res;
    };
  }

  if (!Array.prototype.forEach) {
    Array.prototype.forEach = function(fun /*, thisp*/) {
      var len = this.length;
      if (typeof fun != "function")
        throw new TypeError();

      var thisp = arguments[1];
      for (var i = 0; i < len; i++) {
        if (i in this)
          fun.call(thisp, this[i], i, this);
      }
    };
  }

  function SoundMetrics(attributes) {
    this.peakLevel = attributes["PeakLevel"];
  }

  SoundMetrics.prototype.getPeakDB = function() {
    return 10 * Math.log(this.peakLevel) / 2.302585092994046;
  };

  display = document.getElementById("soundmeter")

  var Socket = "MozWebSocket" in window ? MozWebSocket : WebSocket;
  var ws = new Socket("ws://localhost:9000/soundmeter.ws");
  ws.onmessage = function(evt) {
     metrics = eval(evt.data).map(function(attributes) {
       return new SoundMetrics(attributes)
     })

     metrics.forEach(function(channelMetrics, channelIndex) {
       channelDisplay = document.getElementById("soundmeter_channel" + channelIndex)
       var peakDB = channelMetrics.getPeakDB();
       var width = 0

       if (peakDB > -40) {
         width = (peakDB + 40) / 40.0 * 200;
       }

       /* channelDisplay.innerHTML = peakDB; */
       channelDisplay.style.width = width + "px";
     })
  };
  ws.onclose = function() { console.log("socket closed"); };
</script>
</body>