convolver-upmixing-1-channel-response.html

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This WPT test may be referenced by the following Test IDs:
- /webaudio/the-audio-api/the-convolvernode-interface/convolver-upmixing-1-channel-response.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Test that up-mixing signals in ConvolverNode processing is linear</title>

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

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

<script>

const EPSILON = 3.0 * Math.pow(2, -22);

// sampleRate is a power of two so that delay times are exact in base-2

// floating point arithmetic.

const SAMPLE_RATE = 32768;

// Length of stereo convolver input in frames (arbitrary):

const STEREO_FRAMES = 256;

// Length of mono signal in frames.  This is more than two blocks to ensure

// that at least one block will be mono, even if interpolation in the

// DelayNode means that stereo is output one block earlier and later than

// if frames are delayed without interpolation.

const MONO_FRAMES = 384;

// Length of response buffer:

const RESPONSE_FRAMES = 256;

function test_linear_upmixing(channelInterpretation, initial_mono_frames)

  let stereo_input_end = initial_mono_frames + STEREO_FRAMES;

  // Total length:

  let length = stereo_input_end + RESPONSE_FRAMES + MONO_FRAMES + STEREO_FRAMES;

  // The first two channels contain signal where some up-mixing occurs

  // internally to a ConvolverNode when a stereo signal is added and removed.

  // The last two channels are expected to contain the same signal, but mono

  // and stereo signals are convolved independently before up-mixing the mono

  // output to mix with the stereo output.

  let context = new OfflineAudioContext({numberOfChannels: 4,

                                         length: length,

                                         sampleRate: SAMPLE_RATE});

  let response = new AudioBuffer({numberOfChannels: 1,

                                  length: RESPONSE_FRAMES,

                                  sampleRate: context.sampleRate});

  // Two stereo channel splitters will collect test and reference outputs.

  let destinationMerger = new ChannelMergerNode(context, {numberOfInputs: 4});

  destinationMerger.connect(context.destination);

  let testSplitter =

      new ChannelSplitterNode(context, {numberOfOutputs: 2});

  let referenceSplitter =

      new ChannelSplitterNode(context, {numberOfOutputs: 2});

  testSplitter.connect(destinationMerger, 0, 0);

  testSplitter.connect(destinationMerger, 1, 1);

  referenceSplitter.connect(destinationMerger, 0, 2);

  referenceSplitter.connect(destinationMerger, 1, 3);

  // A GainNode mixes reference stereo and mono signals because up-mixing

  // cannot be performed at a channel splitter.

  let referenceGain = new GainNode(context);

  referenceGain.connect(referenceSplitter);

  referenceGain.channelInterpretation = channelInterpretation;

  // The impulse response for convolution contains two impulses so as to test

  // effects in at least two processing blocks.

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

  response.getChannelData(0)[response.length - 1] = 0.5;

  let testConvolver = new ConvolverNode(context, {disableNormalization: true,

                                                  buffer: response});

  testConvolver.channelInterpretation = channelInterpretation;

  let referenceMonoConvolver = new ConvolverNode(context,

                                                 {disableNormalization: true,

                                                  buffer: response});

  let referenceStereoConvolver = new ConvolverNode(context,

                                                   {disableNormalization: true,

                                                    buffer: response});

  // No need to set referenceStereoConvolver.channelInterpretation because

  // input is either silent or stereo.

  testConvolver.connect(testSplitter);

  // Mix reference convolver output.

  referenceMonoConvolver.connect(referenceGain);

  referenceStereoConvolver.connect(referenceGain);

  // The DelayNode initially has a single channel of silence, which is used to

  // switch the stereo signal in and out.  The output of the delay node is

  // first mono silence (if there is a non-zero initial_mono_frames), then

  // stereo, then mono silence, and finally stereo again.  maxDelayTime is

  // used to generate the middle mono silence period from the initial silence

  // in the DelayNode and then generate the final period of stereo from its

  // initial input.

  let maxDelayTime = (length - STEREO_FRAMES) / context.sampleRate;

  let delay =

      new DelayNode(context,

                    {maxDelayTime: maxDelayTime,

                     delayTime: initial_mono_frames / context.sampleRate});

  // Schedule an increase in the delay to return to mono silence.

  delay.delayTime.setValueAtTime(maxDelayTime,

                                 stereo_input_end / context.sampleRate);

  delay.connect(testConvolver);

  delay.connect(referenceStereoConvolver);

  let stereoMerger = new ChannelMergerNode(context, {numberOfInputs: 2});

  stereoMerger.connect(delay);

  // Three independent signals

  let monoSignal = new OscillatorNode(context, {frequency: 440});

  let leftSignal = new OscillatorNode(context, {frequency: 450});

  let rightSignal = new OscillatorNode(context, {frequency: 460});

  monoSignal.connect(testConvolver);

  monoSignal.connect(referenceMonoConvolver);

  leftSignal.connect(stereoMerger, 0, 0);

  rightSignal.connect(stereoMerger, 0, 1);

  monoSignal.start();

  leftSignal.start();

  rightSignal.start();

  return context.startRendering().

    then((buffer) => {

      let maxDiff = -1.0;

      let frameIndex = 0;

      let channelIndex = 0;

      for (let c = 0; c < 2; ++c) {

        let testOutput = buffer.getChannelData(0 + c);

        let referenceOutput = buffer.getChannelData(2 + c);

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

          var diff = Math.abs(testOutput[i] - referenceOutput[i]);

          if (diff > maxDiff) {

            maxDiff = diff;

            frameIndex = i;

            channelIndex = c;

      assert_approx_equals(buffer.getChannelData(0 + channelIndex)[frameIndex],

                           buffer.getChannelData(2 + channelIndex)[frameIndex],

                           EPSILON,

                           `output at ${frameIndex} ` +

                             `in channel ${channelIndex}` );

});

promise_test(() => test_linear_upmixing("speakers", MONO_FRAMES),

             "speakers, initially mono");

promise_test(() => test_linear_upmixing("discrete", MONO_FRAMES),

             "discrete");

// Gecko uses a separate path for "speakers" up-mixing when the convolver's

// first input is stereo, so test that separately.

promise_test(() => test_linear_upmixing("speakers", 0),

             "speakers, initially stereo");

</script>