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The Tor Browser
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test_mediaElementAudioSourceNodeFidelity.html (4533B)

      1 <!DOCTYPE HTML>
      2 <html>
      3 <meta charset="utf-8">
      4 <head>
      5  <title>Test MediaStreamAudioSourceNode doesn't get data from cross-origin media resources</title>
      6  <script src="/tests/SimpleTest/SimpleTest.js"></script>
      7  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
      8 </head>
      9 <body>
     10 <pre id="test">
     11 <script class="testbody" type="text/javascript">
     12 SimpleTest.waitForExplicitFinish();
     13 
     14 function binIndexForFrequency(frequency, analyser) {
     15  return 1 + Math.round(frequency *
     16                        analyser.fftSize /
     17                        analyser.context.sampleRate);
     18 }
     19 
     20 function debugCanvas(analyser) {
     21  var cvs = document.createElement("canvas");
     22  document.body.appendChild(cvs);
     23 
     24  // Easy: 1px per bin
     25  cvs.width = analyser.frequencyBinCount;
     26  cvs.height = 256;
     27  cvs.style.border = "1px solid red";
     28 
     29  var c = cvs.getContext('2d');
     30  var buf = new Uint8Array(analyser.frequencyBinCount);
     31 
     32  function render() {
     33    c.clearRect(0, 0, cvs.width, cvs.height);
     34    analyser.getByteFrequencyData(buf);
     35    for (var i = 0; i < buf.length; i++) {
     36      c.fillRect(i, (256 - (buf[i])), 1, 256);
     37    }
     38    requestAnimationFrame(render);
     39  }
     40  requestAnimationFrame(render);
     41 }
     42 
     43 
     44 function checkFrequency(an) {
     45  an.getFloatFrequencyData(frequencyArray);
     46  // We should have no energy when checking the data largely outside the index
     47  // for 440Hz (the frequency of the sine wave), start checking an octave above,
     48  // the Opus compression can add some harmonics to the pure since wave.
     49  var maxNoiseIndex = binIndexForFrequency(880, an);
     50  for (var i = maxNoiseIndex + 1; i < frequencyArray.length; i++) {
     51    if (frequencyArray[i] > frequencyArray[maxNoiseIndex]) {
     52       maxNoiseIndex = i;
     53    }
     54  }
     55 
     56  // On the other hand, we should find a peak at 440Hz. Our sine wave is not
     57  // attenuated, we're expecting the peak to reach 0dBFs.
     58  var index = binIndexForFrequency(440, an);
     59  info("energy at 440: " + frequencyArray[index] +
     60       ", threshold " + (an.maxDecibels - 10) +
     61       "; max noise at index " + maxNoiseIndex +
     62       ": " + frequencyArray[maxNoiseIndex] );
     63  if (frequencyArray[index] < (an.maxDecibels - 10)) {
     64    return false;
     65  }
     66  // Let some slack, there might be some noise here because of int -> float
     67  // conversion or the Opus encoding.
     68  if (frequencyArray[maxNoiseIndex] > an.minDecibels + 40) {
     69    return false;
     70  }
     71 
     72  return true;
     73 }
     74 
     75 var audioElement = new Audio();
     76 audioElement.src = 'sine-440-10s.opus'
     77 audioElement.loop = true;
     78 var ac = new AudioContext();
     79 var mediaElementSource = ac.createMediaElementSource(audioElement);
     80 var an = ac.createAnalyser();
     81 // Use no smoothing as this would just average with previous
     82 // getFloatFrequencyData() calls.  Non-seamless looping would introduce noise,
     83 // and smoothing would spread this into calls after the loop point.
     84 an.smoothingTimeConstant = 0;
     85 let frequencyArray = new Float32Array(an.frequencyBinCount);
     86 
     87 // Uncomment this to check what the analyser is doing.
     88 // debugCanvas(an);
     89 
     90 mediaElementSource.connect(an)
     91 
     92 audioElement.play();
     93 // We want to check the we have the expected audio for at least two loop of
     94 // the HTMLMediaElement, piped into an AudioContext. The file is ten seconds,
     95 // and we use the default FFT size.
     96 var lastCurrentTime = 0;
     97 var loopCount = 0;
     98 audioElement.onplaying = function() {
     99  audioElement.ontimeupdate = function() {
    100    // We don't run the analysis when close to loop point or at the
    101    // beginning, since looping is not seamless, there could be an
    102    // unpredictable amount of silence
    103    var rv = checkFrequency(an);
    104    info("currentTime: " + audioElement.currentTime);
    105    if (audioElement.currentTime < 4 ||
    106        audioElement.currentTime > 8){
    107      return;
    108    }
    109    if (!rv) {
    110      ok(false, "Found unexpected noise during analysis.");
    111      audioElement.ontimeupdate = null;
    112      audioElement.onplaying = null;
    113      ac.close();
    114      audioElement.src = '';
    115      SimpleTest.finish()
    116      return;
    117    }
    118    ok(true, "Found correct audio signal during analysis");
    119    info(lastCurrentTime + " " + audioElement.currentTime);
    120    if (lastCurrentTime > audioElement.currentTime) {
    121      info("loopCount: " + loopCount);
    122      if (loopCount > 1) {
    123        audioElement.ontimeupdate = null;
    124        audioElement.onplaying = null;
    125        ac.close();
    126        audioElement.src = '';
    127        SimpleTest.finish();
    128      }
    129      lastCurrentTime = audioElement.currentTime;
    130      loopCount++;
    131    } else {
    132      lastCurrentTime = audioElement.currentTime;
    133    }
    134  }
    135 }
    136 
    137 </script>