File: maxdelay-rounding.html

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<!DOCTYPE html>
<html>
  <head>
    <title>
      Test DelayNode when maxDelayTime requires rounding
    </title>
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
    <script src="/webaudio/resources/audit-util.js"></script>
  </head>
  <body>
    <script>
      const sampleRate = 44100;
      const inputLengthSeconds = 1;
      const renderLengthSeconds = 2;

      // Delay for one second plus 0.4 of a sample frame, to test that
      // DelayNode is properly rounding up when calculating its buffer
      // size (crbug.com/1065110).
      const delayTimeSeconds = 1 + 0.4 / sampleRate;

      promise_test(async () => {
        const context = new OfflineAudioContext({
          numberOfChannels: 1,
          length: sampleRate * renderLengthSeconds,
          sampleRate: sampleRate,
        });

        // Create a constant source to use as input.
        const src = new ConstantSourceNode(context);

        // Create a DelayNode to delay for delayTimeSeconds.
        const delay = new DelayNode(context, {
          maxDelayTime: delayTimeSeconds,
          delayTime: delayTimeSeconds,
        });

        src.connect(delay).connect(context.destination);

        src.start();
        const renderedBuffer = await context.startRendering();
        const renderedData = renderedBuffer.getChannelData(0);

        // The first delayTimeSeconds of output should be silent.
        const expectedSilentFrames = Math.floor(
            delayTimeSeconds * sampleRate);

        assert_constant_value(
            renderedData.slice(0, expectedSilentFrames),
            0,
            `output[0:${expectedSilentFrames - 1}]`);

        // The rest should be non-silent: that is, there should
        // be at least one non-zero sample.  (Any reasonable
        // interpolation algorithm will make all these samples
        // non-zero, but I don't think that's guaranteed by the
        // spec, so we use a conservative test for now.)
        assert_not_constant_value_of(
            renderedData.slice(expectedSilentFrames),
            0,
            `output[${expectedSilentFrames}:]`);
      }, 'Test DelayNode when maxDelayTime requires rounding');
    </script>
  </body>
</html>