test_convolverNodeDelay.html

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<!DOCTYPE html>

<title>Test convolution to delay a triangle pulse</title>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script>

const sampleRate = 48000;

const LENGTH = 12800;

// tolerate 16-bit math.

const EPSILON = 1.0 / Math.pow(2, 15);

// Triangle pulse

var sourceBuffer = new OfflineAudioContext(1, 1, sampleRate).

  createBuffer(1, 2 * 128, sampleRate);

var channelData = sourceBuffer.getChannelData(0);

for (var i = 0; i < 128; ++i) {

  channelData[i] = i/128;

  channelData[128 + i] = 1.0 - i/128;

function test_delay_index(delayIndex) {

  var context = new OfflineAudioContext(2, LENGTH, sampleRate);

  var merger = context.createChannelMerger(2);

  merger.connect(context.destination);

  var impulse = context.createBuffer(1, delayIndex + 1, sampleRate);

  impulse.getChannelData(0)[delayIndex] = 1.0;

  var convolver = context.createConvolver();

  convolver.normalize = false;

  convolver.buffer = impulse;

  convolver.connect(merger, 0, 0);

  var delayTime = delayIndex/sampleRate;

  var delay = context.createDelay(delayTime || 1/sampleRate);

  delay.delayTime.value = delayTime;

  delay.connect(merger, 0, 1);

  var source = context.createBufferSource();

  source.buffer = sourceBuffer;

  source.connect(convolver);

  source.connect(delay);

  source.start(0);

  return context.startRendering().

    then((buffer) => {

      var convolverOutput = buffer.getChannelData(0);

      var delayOutput = buffer.getChannelData(1);

      var maxDiff = 0.0;

      var maxIndex = 0;

      for (var i = 0; i < buffer.length; ++i) {

        var diff = Math.abs(convolverOutput[i] - delayOutput[i]);

        if (diff > maxDiff) {

          maxDiff = diff;

          maxIndex = i;

      // The convolver should produce similar output to the delay.

      assert_approx_equals(convolverOutput[maxIndex], delayOutput[maxIndex],

                           EPSILON, "output at " + maxIndex);

});

// The 5/4 ratio provides sampling across a range of delays and offsets within

// blocks.

for (var delayIndex = 0;

     delayIndex < LENGTH;

     delayIndex = Math.floor((5 * (delayIndex + 1)) / 4)) {

  promise_test(test_delay_index.bind(null, delayIndex),

               "Delay " + delayIndex);

</script>