1 files changed, 172 insertions, 0 deletions
diff --git a/testing/web-platform/tests/webaudio/resources/biquad-testing.js b/testing/web-platform/tests/webaudio/resources/biquad-testing.js
new file mode 100644
index 0000000000..7f90a1f72b
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+++ b/testing/web-platform/tests/webaudio/resources/biquad-testing.js
@@ -0,0 +1,172 @@
+// Globals, to make testing and debugging easier.
+let context;
+let filter;
+let signal;
+let renderedBuffer;
+let renderedData;
+
+// Use a power of two to eliminate round-off in converting frame to time
+let sampleRate = 32768;
+let pulseLengthFrames = .1 * sampleRate;
+
+// Maximum allowed error for the test to succeed.  Experimentally determined.
+let maxAllowedError = 5.9e-8;
+
+// This must be large enough so that the filtered result is essentially zero.
+// See comments for createTestAndRun.  This must be a whole number of frames.
+let timeStep = Math.ceil(.1 * sampleRate) / sampleRate;
+
+// Maximum number of filters we can process (mostly for setting the
+// render length correctly.)
+let maxFilters = 5;
+
+// How long to render.  Must be long enough for all of the filters we
+// want to test.
+let renderLengthSeconds = timeStep * (maxFilters + 1);
+
+let renderLengthSamples = Math.round(renderLengthSeconds * sampleRate);
+
+// Number of filters that will be processed.
+let nFilters;
+
+function createImpulseBuffer(context, length) {
+  let impulse = context.createBuffer(1, length, context.sampleRate);
+  let data = impulse.getChannelData(0);
+  for (let k = 1; k < data.length; ++k) {
+    data[k] = 0;
+  }
+  data[0] = 1;
+
+  return impulse;
+}
+
+
+function createTestAndRun(context, filterType, testParameters) {
+  // To test the filters, we apply a signal (an impulse) to each of
+  // the specified filters, with each signal starting at a different
+  // time.  The output of the filters is summed together at the
+  // output.  Thus for filter k, the signal input to the filter
+  // starts at time k * timeStep.  For this to work well, timeStep
+  // must be large enough for the output of each filter to have
+  // decayed to zero with timeStep seconds.  That way the filter
+  // outputs don't interfere with each other.
+
+  let filterParameters = testParameters.filterParameters;
+  nFilters = Math.min(filterParameters.length, maxFilters);
+
+  signal = new Array(nFilters);
+  filter = new Array(nFilters);
+
+  impulse = createImpulseBuffer(context, pulseLengthFrames);
+
+  // Create all of the signal sources and filters that we need.
+  for (let k = 0; k < nFilters; ++k) {
+    signal[k] = context.createBufferSource();
+    signal[k].buffer = impulse;
+
+    filter[k] = context.createBiquadFilter();
+    filter[k].type = filterType;
+    filter[k].frequency.value =
+        context.sampleRate / 2 * filterParameters[k].cutoff;
+    filter[k].detune.value = (filterParameters[k].detune === undefined) ?
+        0 :
+        filterParameters[k].detune;
+    filter[k].Q.value = filterParameters[k].q;
+    filter[k].gain.value = filterParameters[k].gain;
+
+    signal[k].connect(filter[k]);
+    filter[k].connect(context.destination);
+
+    signal[k].start(timeStep * k);
+  }
+
+  return context.startRendering().then(buffer => {
+    checkFilterResponse(buffer, filterType, testParameters);
+  });
+}
+
+function addSignal(dest, src, destOffset) {
+  // Add src to dest at the given dest offset.
+  for (let k = destOffset, j = 0; k < dest.length, j < src.length; ++k, ++j) {
+    dest[k] += src[j];
+  }
+}
+
+function generateReference(filterType, filterParameters) {
+  let result = new Array(renderLengthSamples);
+  let data = new Array(renderLengthSamples);
+  // Initialize the result array and data.
+  for (let k = 0; k < result.length; ++k) {
+    result[k] = 0;
+    data[k] = 0;
+  }
+  // Make data an impulse.
+  data[0] = 1;
+
+  for (let k = 0; k < nFilters; ++k) {
+    // Filter an impulse
+    let detune = (filterParameters[k].detune === undefined) ?
+        0 :
+        filterParameters[k].detune;
+    let frequency = filterParameters[k].cutoff *
+        Math.pow(2, detune / 1200);  // Apply detune, converting from Cents.
+
+    let filterCoef = createFilter(
+        filterType, frequency, filterParameters[k].q, filterParameters[k].gain);
+    let y = filterData(filterCoef, data, renderLengthSamples);
+
+    // Accumulate this filtered data into the final output at the desired
+    // offset.
+    addSignal(result, y, timeToSampleFrame(timeStep * k, sampleRate));
+  }
+
+  return result;
+}
+
+function checkFilterResponse(renderedBuffer, filterType, testParameters) {
+  let filterParameters = testParameters.filterParameters;
+  let maxAllowedError = testParameters.threshold;
+  let should = testParameters.should;
+
+  renderedData = renderedBuffer.getChannelData(0);
+
+  reference = generateReference(filterType, filterParameters);
+
+  let len = Math.min(renderedData.length, reference.length);
+
+  let success = true;
+
+  // Maximum error between rendered data and expected data
+  let maxError = 0;
+
+  // Sample offset where the maximum error occurred.
+  let maxPosition = 0;
+
+  // Number of infinities or NaNs that occurred in the rendered data.
+  let invalidNumberCount = 0;
+
+  should(nFilters, 'Number of filters tested')
+      .beEqualTo(filterParameters.length);
+
+  // Compare the rendered signal with our reference, keeping
+  // track of the maximum difference (and the offset of the max
+  // difference.)  Check for bad numbers in the rendered output
+  // too.  There shouldn't be any.
+  for (let k = 0; k < len; ++k) {
+    let err = Math.abs(renderedData[k] - reference[k]);
+    if (err > maxError) {
+      maxError = err;
+      maxPosition = k;
+    }
+    if (!isValidNumber(renderedData[k])) {
+      ++invalidNumberCount;
+    }
+  }
+
+  should(
+      invalidNumberCount, 'Number of non-finite values in the rendered output')
+      .beEqualTo(0);
+
+  should(maxError, 'Max error in ' + filterTypeName[filterType] + ' response')
+      .beLessThanOrEqualTo(maxAllowedError);
+}