<!DOCTYPE HTML>
<html>
<head>
  <title>Test left/right symmetry and block-offset invariance of HRTF panner</title>
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <script type="text/javascript" src="webaudio.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
</head>
<body>
<pre id="test">
<script class="testbody" type="text/javascript">

SimpleTest.waitForExplicitFinish();

const blockSize = 128;
const bufferSize = 4096; // > HRTF panner latency

var ctx = new AudioContext();

function isChannelSilent(channel) {
  for (var i = 0; i < channel.length; ++i) {
    if (channel[i] != 0.0) {
      return false;
    }
  }
  return true;
}

function startTest() {
  var leftPanner = ctx.createPanner();
  var rightPanner = ctx.createPanner();
  leftPanner.panningModel = "HRTF";
  rightPanner.panningModel = "HRTF";
  leftPanner.positionX.value = -1;
  rightPanner.positionX.value = 1;

  // Test that PannerNode processes the signal consistently irrespective of
  // the offset in the processing block.  This is done by inserting a delay of
  // less than a block size before one panner.
  const delayTime = 0.7 * blockSize / ctx.sampleRate;
  var leftDelay = ctx.createDelay(delayTime);
  leftDelay.delayTime.value = delayTime;
  leftDelay.connect(leftPanner);
  // and compensating for the delay after the other.
  var rightDelay = ctx.createDelay(delayTime);
  rightDelay.delayTime.value = delayTime;
  rightPanner.connect(rightDelay);

  // Feed the panners with a signal having some harmonics to fill the spectrum.
  var oscillator = ctx.createOscillator();
  oscillator.frequency.value = 110;
  oscillator.type = "sawtooth";
  oscillator.connect(leftDelay);
  oscillator.connect(rightPanner);
  oscillator.start(0);

  // Switch the channels on one panner output, and it should match the other.
  var splitter = ctx.createChannelSplitter();
  leftPanner.connect(splitter);
  var merger = ctx.createChannelMerger();
  splitter.connect(merger, 0, 1);
  splitter.connect(merger, 1, 0);

  // Invert one signal so that mixing with the other will find the difference.
  var gain = ctx.createGain();
  gain.gain.value = -1.0;
  merger.connect(gain);

  var processor = ctx.createScriptProcessor(bufferSize, 2, 0);
  gain.connect(processor);
  rightDelay.connect(processor);
  processor.onaudioprocess =
    function(e) {
      compareBuffers(e.inputBuffer,
                     ctx.createBuffer(2, bufferSize, ctx.sampleRate));
      e.target.onaudioprocess = null;
      SimpleTest.finish();
    }
}

function prepareTest() {
  // A PannerNode will produce no output until it has loaded its HRIR
  // database.  Wait for this to load before starting the test.
  var processor = ctx.createScriptProcessor(bufferSize, 2, 0);
  var panner = ctx.createPanner();
  panner.panningModel = "HRTF";
  panner.connect(processor);
  var oscillator = ctx.createOscillator();
  oscillator.connect(panner);
  oscillator.start(0);

  processor.onaudioprocess =
    function(e) {
      if (isChannelSilent(e.inputBuffer.getChannelData(0)))
        return;

      oscillator.stop(0);
      panner.disconnect();
      e.target.onaudioprocess = null;
      startTest();
    };
}
prepareTest();
</script>
</pre>
</body>
</html>
