Chromium Web Audio Layout Test prototypes for Canopy

audiobuffersource-loop-points.js

// @channels 3
// @sampleRate 128000
// @duration 1.5


function pitchToFrequency(pitch) {
  return 440 * Math.pow(2, (Math.floor(pitch)-69)/12);
}

function pitchToPlaybackRate(pitch) {
  return Math.pow(2, pitch/12);
}

function createSineWaveBuffer(context, frequency, duration) {
  var length = duration * context.sampleRate;
  var buffer = context.createBuffer(1, length, context.sampleRate);
  var data = buffer.getChannelData(0);
  var base = 2 * Math.PI * frequency / context.sampleRate;
  for (var i = 0; i < data.length; i++)
    data[i] = Math.sin(base * i);
  
  return buffer;
}

var basePitch = 36;
var baseFrequency = pitchToFrequency(basePitch);
var testBuffer = createSineWaveBuffer(context, baseFrequency, 2 / baseFrequency);
console.log(testBuffer.duration);
var unitDuration = 0.025;


function runUnitTest(context, unitStart, unitPitch) {
  var source1 = context.createBufferSource();
  var source2 = context.createBufferSource();
  var inverter = context.createGain();
  var merger = context.createChannelMerger(3);
  var env = context.createGain();
  
  var expectedBuffer = createSineWaveBuffer(context, pitchToFrequency(unitPitch), unitDuration);
  var targetRate = pitchToPlaybackRate(unitPitch - basePitch); 

  source1.buffer = expectedBuffer;
  source1.loop = true;
  
  source2.buffer = testBuffer;
  source2.playbackRate.value = targetRate;
  source2.loop = true;
  source2.loopStart = 0.5 * testBuffer.duration;
  source2.loopEnd = testBuffer.duration;
  
  inverter.gain.value = -1.0;  
  
  source1.connect(merger, 0, 0);
  source2.connect(merger, 0, 1);
  source1.connect(merger, 0, 2);
  source2.connect(inverter);
  inverter.connect(merger, 0, 2);
  merger.connect(env);
  env.connect(context.destination);
  
  source1.start(unitStart);
  source1.stop(unitStart + unitDuration);
  source2.start(unitStart);
  source2.stop(unitStart + unitDuration);
  // env.gain.setValueAtTime(1.0, unitStart);
  // env.gain.setValueAtTime(1.0, unitStart + unitDuration - 0.005);
  // env.gain.linearRampToValueAtTime(0.0, unitStart + unitDuration);
}

for (var iteration = 0; iteration < 60; iteration++) {
  (function (i) {
    context.suspend(unitDuration * i).then(function () {
      runUnitTest(context, unitDuration * i, basePitch + i);
      context.resume();
    });
  })(iteration);
}

context.oncomplete = function (event) {
  var data = event.renderedBuffer.getChannelData(2);
  var maxDiff = 0, index = -1;
  for (var i = 0; i < data.length; i++) {
    var diff = Math.abs(data[i]);
    if (diff > maxDiff) {
      maxDiff = diff;
      index = i;
    }
  }
  
  console.log('MAXDIFF = ' + maxDiff.toExponential() + ' (' + index + ')');
}

audiobuffersource-playbackrate.js

// @sampleRate 44160
// @duration 1.5

function pitchToFrequency(pitch) {
  return 440 * Math.pow(2, (Math.floor(pitch)-69)/12);
}

function pitchToRate(pitch) {
  return Math.pow(2, pitch/12);
}

function createSineWaveBuffer(context, frequency, duration) {
  var length = duration * context.sampleRate;
  var buffer = context.createBuffer(1, length, context.sampleRate);
  var data = buffer.getChannelData(0);
  var phase = 0, base = 2 * Math.PI * frequency / context.sampleRate;
  for (var i = 0; i < length; i++)
    data[i] = Math.sin(base * i);
  
  return buffer;
}

var testBuffer = createSineWaveBuffer(context, pitchToFrequency(36), 5);
var testDuration = 0.025;

function test(context, testStart, testPitch) {
  var source1 = context.createBufferSource();
  var source2 = context.createBufferSource();
  var inverter = context.createGain();

  source1.buffer = createSineWaveBuffer(context, pitchToFrequency(testPitch), testDuration);
  source2.buffer = testBuffer;
  source2.playbackRate.value = pitchToRate(testPitch - 36);
  inverter.gain.value = -1.0;

  source1.connect(context.destination);
  source2.connect(inverter)
  inverter.connect(context.destination);

  source1.start(testStart);
  source1.stop(testStart + testDuration);
  source2.start(testStart);
  source2.stop(testStart + testDuration);
}

function onsuspended(iteration) {
  return function () {
    console.log('pitch = ', 36 + iteration);
    test(context, testDuration * iteration, 36 + iteration);
    context.resume();
  };
}

// batch scheduling
for (var s = 0; s < 60; s++) {
  context.suspend(testDuration * s).then(onsuspended(s));
}

context.oncomplete = function (event) {
  var data = event.renderedBuffer.getChannelData(0);
  var maxDiff = 0;
  for (var i = 0; i < data.length; i++) {
    var diff = Math.abs(data[i]);
    if (diff > maxDiff)
      maxDiff = diff;
  }
  
  console.log("MAXDIFF = ", maxDiff);
};