test_sequentialBufferSourceWithResampling.html

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<!DOCTYPE html>

<title>Test seamless playback of a series of resampled buffers</title>

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

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

<script>

// Permitting some accumulation of rounding to int16_t.

// 64/2^15 would be only just small enough to detect off-by-one-subsample

// scheduling errors with the frequencies here.

const EPSILON = 4.0 / Math.pow(2, 15);

// Offsets test for rounding to nearest rather than up or down.

const OFFSETS = [EPSILON, 1.0 - EPSILON];

// The ratio of resampling is 147:160, so 256 start points is enough to cover

// every fractional offset.

const LENGTH = 256;

function do_test(context_rate, buffer_rate, start_offset) {

  var context =

    new OfflineAudioContext(2, LENGTH, context_rate);

  var merger = context.createChannelMerger(context.destination.channelCount);

  merger.connect(context.destination);

  // Create an audio signal that will be repeated

  var repeating_signal = context.createBuffer(1, 1, buffer_rate);

  repeating_signal.getChannelData(0)[0] = 0.5;

  // Schedule a series of nodes to repeat the signal.

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

    var source = context.createBufferSource();

    source.buffer = repeating_signal;

    source.connect(merger, 0, 0);

    source.start((i + start_offset) / buffer_rate);

  // A single long signal should produce the same result.

  var long_signal = context.createBuffer(1, LENGTH, buffer_rate);

  var c = long_signal.getChannelData(0);

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

    c[i] = 0.5;

  var source = context.createBufferSource();

  source.buffer = long_signal;

  source.connect(merger, 0, 1);

  source.start(start_offset / buffer_rate);

  return context.startRendering().

    then((buffer) => {

      let series_output = buffer.getChannelData(0);

      let expected = buffer.getChannelData(1);

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

        assert_approx_equals(series_output[i], expected[i], EPSILON,

                             "series output at " + i);

});

function start_tests(context_rate, buffer_rate) {

  OFFSETS.forEach((start_offset) => {

    promise_test(() => do_test(context_rate, buffer_rate, start_offset),

                 "" + context_rate + " context, "

                 + buffer_rate + " buffer, "

                 + start_offset + " start");

});

start_tests(48000, 44100);

start_tests(44100, 48000);

</script>