sample-accurate-scheduling.html

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This WPT test may be referenced by the following Test IDs:
- /webaudio/the-audio-api/the-audiobuffersourcenode-interface/sample-accurate-scheduling.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<!--

Tests that we are able to schedule a series of notes to playback with sample-accuracy.

We use an impulse so we can tell exactly where the rendering is happening.

-->

<html>

  <head>

    <title>

      sample-accurate-scheduling.html

    </title>

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

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

    <script src="/webaudio/resources/audit-util.js"></script>

    <script src="/webaudio/resources/audit.js"></script>

  </head>

  <body>

    <script id="layout-test-code">

      let audit = Audit.createTaskRunner();

      let sampleRate = 44100.0;

      let lengthInSeconds = 4;

      let context = 0;

      let bufferLoader = 0;

      let impulse;

      // See if we can render at exactly these sample offsets.

      let sampleOffsets = [0, 3, 512, 517, 1000, 1005, 20000, 21234, 37590];

      function createImpulse() {

        // An impulse has a value of 1 at time 0, and is otherwise 0.

        impulse = context.createBuffer(2, 512, sampleRate);

        let sampleDataL = impulse.getChannelData(0);

        let sampleDataR = impulse.getChannelData(1);

        sampleDataL[0] = 1.0;

        sampleDataR[0] = 1.0;

      function playNote(time) {

        let bufferSource = context.createBufferSource();

        bufferSource.buffer = impulse;

        bufferSource.connect(context.destination);

        bufferSource.start(time);

      function checkSampleAccuracy(buffer, should) {

        let bufferDataL = buffer.getChannelData(0);

        let bufferDataR = buffer.getChannelData(1);

        let impulseCount = 0;

        let badOffsetCount = 0;

        // Left and right channels must be the same.

        should(bufferDataL, 'Content of left and right channels match and')

            .beEqualToArray(bufferDataR);

        // Go through every sample and make sure it's 0, except at positions in

        // sampleOffsets.

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

          if (bufferDataL[i] != 0) {

            // Make sure this index is  in sampleOffsets

            let found = false;

            for (let j = 0; j < sampleOffsets.length; ++j) {

              if (sampleOffsets[j] == i) {

                found = true;

                break;

            ++impulseCount;

            should(found, 'Non-zero sample found at sample offset ' + i)

                .beTrue();

            if (!found) {

              ++badOffsetCount;

        should(impulseCount, 'Number of impulses found')

            .beEqualTo(sampleOffsets.length);

        if (impulseCount == sampleOffsets.length) {

          should(badOffsetCount, 'bad offset').beEqualTo(0);

      audit.define(

          {label: 'test', description: 'Test sample-accurate scheduling'},

          function(task, should) {

            // Create offline audio context.

            context = new OfflineAudioContext(

                2, sampleRate * lengthInSeconds, sampleRate);

            createImpulse();

            for (let i = 0; i < sampleOffsets.length; ++i) {

              let timeInSeconds = sampleOffsets[i] / sampleRate;

              playNote(timeInSeconds);

            context.startRendering().then(function(buffer) {

              checkSampleAccuracy(buffer, should);

              task.done();

});

});

      audit.run();

    </script>

  </body>

</html>