audiobuffersource-playbackrate-zero.html

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This test has a WPT meta file that expects 6 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-playbackrate-zero.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<html>

  <head>

    <title>

      audiobuffersource-playbackrate-zero.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">

      // Sample rate should be power of 128 to observe the change of AudioParam

      // at the beginning of rendering quantum. (playbackRate is k-rate) This is

      // the minimum sample rate in the valid sample rate range.

      let sampleRate = 8192;

      // The render duration in seconds, and the length in samples.

      let renderDuration = 1.0;

      let renderLength = renderDuration * sampleRate;

      let context = new OfflineAudioContext(1, renderLength, sampleRate);

      let audit = Audit.createTaskRunner();

      // Task: Render the actual buffer and compare with the reference.

      audit.define('synthesize-verify', (task, should) => {

        let ramp = context.createBufferSource();

        let rampBuffer = createLinearRampBuffer(context, renderLength);

        ramp.buffer = rampBuffer;

        ramp.connect(context.destination);

        ramp.start();

        // Leave the playbackRate as 1 for the first half, then change it

        // to zero at the exact half. The zero playback rate should hold the

        // sample value of the buffer index at the moment. (sample-and-hold)

        ramp.playbackRate.setValueAtTime(1.0, 0.0);

        ramp.playbackRate.setValueAtTime(0.0, renderDuration / 2);

        context.startRendering()

            .then(function(renderedBuffer) {

              let data = renderedBuffer.getChannelData(0);

              let rampData = rampBuffer.getChannelData(0);

              let half = rampData.length / 2;

              let passed = true;

              let i;

              for (i = 1; i < rampData.length; i++) {

                if (i < half) {

                  // Before the half position, the actual should match with the

                  // original ramp data.

                  if (data[i] !== rampData[i]) {

                    passed = false;

                    break;

                } else {

                  // From the half position, the actual value should not change.

                  if (data[i] !== rampData[half]) {

                    passed = false;

                    break;

              should(passed, 'The zero playbackRate')

                  .message(

                      'held the sample value correctly',

                      'should hold the sample value. ' +

                          'Expected ' + rampData[half] + ' but got ' + data[i] +

                          ' at the index ' + i);

})

            .then(() => task.done());

});

      audit.define('subsample start with playback rate 0', (task, should) => {

        let context = new OfflineAudioContext(1, renderLength, sampleRate);

        let rampBuffer = new AudioBuffer(

            {length: renderLength, sampleRate: context.sampleRate});

        let data = new Float32Array(renderLength);

        let startValue = 5;

        for (let k = 0; k < data.length; ++k) {

          data[k] = k + startValue;

        rampBuffer.copyToChannel(data, 0);

        let src = new AudioBufferSourceNode(

            context, {buffer: rampBuffer, playbackRate: 0});

        src.connect(context.destination);

        // Purposely start the source between frame boundaries

        let startFrame = 27.3;

        src.start(startFrame / context.sampleRate);

        context.startRendering()

            .then(audioBuffer => {

              let actualStartFrame = Math.ceil(startFrame);

              let audio = audioBuffer.getChannelData(0);

              should(

                  audio.slice(0, actualStartFrame),

                  `output[0:${actualStartFrame - 1}]`)

                  .beConstantValueOf(0);

              should(

                  audio.slice(actualStartFrame), `output[${actualStartFrame}:]`)

                  .beConstantValueOf(startValue);

})

            .then(() => task.done());

});

      audit.run();

    </script>

  </body>

</html>