audioworkletnode-channel-count.https.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /webaudio/the-audio-api/the-audioworklet-interface/audioworkletnode-channel-count.https.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<html>

  <head>

    <title>

      Test AudioWorkletNode's dynamic channel count feature

    </title>

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

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

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

  </head>

  <body>

    <script>

      // Arbitrary numbers used to align the test with render quantum boundary.

      const sampleRate = RENDER_QUANTUM_FRAMES * 100;

      const renderLength = RENDER_QUANTUM_FRAMES * 2;

      const filePath = 'processors/gain-processor.js';

      const testChannelValues = [1, 2, 3];

      // Creates a 3-channel source and play with ConstantSourceNode.

      // The source goes through a bypass AudioWorkletNode (gain value of 1).

      // Verifies if the rendered buffer has all zero for the first half

      // (before 128 samples) and the expected values for the second half.

      promise_test(async () => {

        const context = new OfflineAudioContext(

            testChannelValues.length,

            renderLength,

            sampleRate);

        // Explicitly sets the destination channelCountMode and

        // channelInterpretation to make sure the result does no mixing.

        context.channelCountMode = 'explicit';

        context.channelInterpretation = 'discrete';

        await context.audioWorklet.addModule(filePath);

        const gainWorkletNode = new AudioWorkletNode(context, 'gain');

        gainWorkletNode.parameters.get('gain').value = 1.0;

        // Create a ChannelMergerNode to combine multiple ConstantSourceNodes

        const merger = new ChannelMergerNode(

            context, {numberOfInputs: testChannelValues.length});

        merger.connect(gainWorkletNode);

        gainWorkletNode.connect(context.destination);

        // Create a ConstantSourceNode for each channel with its

        // corresponding value

        const constantSources = testChannelValues.map((value, index) => {

          const constantSource =

              new ConstantSourceNode(context, {offset: value});

          constantSource.connect(merger, 0, index);

          return constantSource;

});

        // Suspend the context at 128 sample frames and start the sources.

        context.suspend(RENDER_QUANTUM_FRAMES/sampleRate).then(() => {

          constantSources.forEach(source => source.start());

          context.resume();

});

        const renderedBuffer = await context.startRendering();

        testChannelValues.forEach((value, index) => {

          const channelData = renderedBuffer.getChannelData(index);

          assert_constant_value(

              channelData.subarray(0, RENDER_QUANTUM_FRAMES),

0,

              'First half of Channel #' + index);

          assert_constant_value(

              channelData.subarray(RENDER_QUANTUM_FRAMES, renderLength),

              value,

              'Second half of Channel #' + index);

});

      }, 'setup-buffer-and-worklet-verify-rendered-buffer');

    </script>

  </body>

</html>