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<!DOCTYPE HTML>
<html>
<head>
  <title>Test for seamless loop of HTMLAudioElements</title>
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
  <script type="text/javascript" src="manifest.js"></script>
</head>
<body>
<canvas id="canvas" width="300" height="300"></canvas>
<script type="application/javascript">
/**
 * This test is used to ensure every time we loop audio, the audio can loop
 * seamlessly which means there won't have any silenece or noise between the
 * end and the start.
 */

SimpleTest.waitForExplicitFinish();

// Set DEBUG to true to add a canvas with a little drawing of what is going
// on, and actually outputs the audio to the speakers.
var DEBUG = true;
var LOOPING_COUNT = 0;
var MAX_LOOPING_COUNT = 10;
var TONE_FREQUENCY = 440;

(async function testSeamlesslooping() {
  info(`- create looping audio element -`);
  let audio = createAudioElement();

  info(`- start audio and analyze audio wave data to ensure looping audio without any silence or noise -`);
  await playAudioAndStartAnalyzingWaveData(audio);

  info(`- test seamless looping multiples times -`);
  for (LOOPING_COUNT = 0; LOOPING_COUNT < MAX_LOOPING_COUNT; LOOPING_COUNT++) {
    await once(audio, "seeked");
    info(`- the round ${LOOPING_COUNT} of the seamless looping succeeds -`);
  }

  info(`- end of seamless looping test -`);
  SimpleTest.finish();
})();

/**
 * Test utility functions
 */
function createSrcBuffer() {
  // Generate the sine in floats, then convert, for simplicity.
  let channels = 1;
  let sampleRate = 44100;
  let buffer = new Float32Array(sampleRate * channels);
  let phase = 0;
  const TAU = 2 * Math.PI;
  for (let i = 0; i < buffer.length; i++) {
    // Adjust the gain a little so we're sure it's not going to clip. This is
    // important because we're converting to 16bit integer right after, and
    // clipping will clearly introduce a discontinuity that will be
    // mischaracterized as a looping click.
    buffer[i] = Math.sin(phase) * 0.99;
    phase += TAU * TONE_FREQUENCY / 44100;
    if (phase > 2 * TAU) {
      phase -= TAU;
    }
  }

  // Make a RIFF header, it's 23 bytes
  let buf = new Int16Array(buffer.length + 23);
  buf[0] = 0x4952;
  buf[1] = 0x4646;
  buf[2] = (2 * buffer.length + 15) & 0x0000ffff;
  buf[3] = ((2 * buffer.length + 15) & 0xffff0000) >> 16;
  buf[4] = 0x4157;
  buf[5] = 0x4556;
  buf[6] = 0x6d66;
  buf[7] = 0x2074;
  buf[8] = 0x0012;
  buf[9] = 0x0000;
  buf[10] = 0x0001;
  buf[11] = 1;
  buf[12] = 44100 & 0x0000ffff;
  buf[13] = (44100 & 0xffff0000) >> 16;
  buf[14] = (2 * channels * sampleRate) & 0x0000ffff;
  buf[15] = ((2 * channels * sampleRate) & 0xffff0000) >> 16;
  buf[16] = 0x0004;
  buf[17] = 0x0010;
  buf[18] = 0x0000;
  buf[19] = 0x6164;
  buf[20] = 0x6174;
  buf[21] = (2 * buffer.length) & 0x0000ffff;
  buf[22] = ((2 * buffer.length) & 0xffff0000) >> 16;

  // convert to int16 and copy.
  for (let i = 0; i < buffer.length; i++) {
    buf[i + 23] = Math.round(buffer[i] * (1 << 15));
  }
  return buf;
}

function createAudioElement() {
  /* global audio */
  window.audio = document.createElement("audio");
  audio.src = URL.createObjectURL(new Blob([createSrcBuffer()],
                                  { type: 'audio/wav' }));
  audio.controls = true;
  audio.loop = true;
  document.body.appendChild(audio);
  return audio;
}

async function playAudioAndStartAnalyzingWaveData(audio) {
  createAudioWaveAnalyser(audio);
  ok(await once(audio, "canplay").then(() => true, () => false),
     `audio can start playing.`)
  ok(await audio.play().then(() => true, () => false),
     `audio started playing successfully.`);
}

function createAudioWaveAnalyser(source) {
  /* global ac, analyser */
  window.ac = new AudioContext();
  window.analyser = ac.createAnalyser();
  analyser.frequencyBuf = new Float32Array(analyser.frequencyBinCount);
  analyser.smoothingTimeConstant = 0;
  analyser.fftSize = 2048; // 1024 bins

  let sourceNode = ac.createMediaElementSource(source);
  sourceNode.connect(analyser);

  if (DEBUG) {
    analyser.connect(ac.destination);
    analyser.timeDomainBuf = new Float32Array(analyser.frequencyBinCount);
    let cvs = document.querySelector("canvas");
    analyser.c = cvs.getContext("2d");
    analyser.w = cvs.width;
    analyser.h = cvs.height;
  }

  analyser.notifyAnalysis = () => {
    if (LOOPING_COUNT >= MAX_LOOPING_COUNT) {
      return;
    }
    let {frequencyBuf} = analyser;
    analyser.getFloatFrequencyData(frequencyBuf);
    // Let things stabilize at the beginning. See bug 1441509.
    if (LOOPING_COUNT > 1) {
      analyser.doAnalysis(frequencyBuf, ac.sampleRate);
    }

    if (DEBUG) {
      let {c, w, h, timeDomainBuf} = analyser;
      c.clearRect(0, 0, w, h);
      analyser.getFloatTimeDomainData(timeDomainBuf);
      for (let i = 0; i < frequencyBuf.length; i++) {
        c.fillRect(i, h, 1, -frequencyBuf[i] + analyser.minDecibels);
      }

      for (let i = 0; i < timeDomainBuf.length; i++) {
        c.fillRect(i, h / 2, 1, -timeDomainBuf[i] * h / 2);
      }
    }

    requestAnimationFrame(analyser.notifyAnalysis);
  }

  analyser.doAnalysis = (buf, ctxSampleRate) => {
    // The size of an FFT is twice the number of bins in its output.
    let fftSize = 2 * buf.length;
    // first find a peak where we expect one.
    let binIndexTone = 1 + Math.round(TONE_FREQUENCY * fftSize / ctxSampleRate);
    ok(buf[binIndexTone] > -25,
       `Could not find a peak: ${buf[binIndexTone]} db at ${TONE_FREQUENCY}Hz`);

    // check that the energy some octaves higher is very low.
    let binIndexOutsidePeak = 1 + Math.round(TONE_FREQUENCY * 4 * buf.length / ctxSampleRate);
    ok(buf[binIndexOutsidePeak] < -110,
       `Found unexpected high frequency content: ${buf[binIndexOutsidePeak]}db at ${TONE_FREQUENCY * 4}Hz`);
  }

  analyser.notifyAnalysis();
}

</script>
</pre>
</body>
</html>