Update web-platform-tests to revision 44702f2bc8ea98bc32b5b244f2fe63c6ce66d49d

tests/wpt/web-platform-tests/webaudio/resources/audioparam-testing.js

@@ -0,0 +1,554 @@
+(function(global) {
+
+  // Information about the starting/ending times and starting/ending values for
+  // each time interval.
+  let timeValueInfo;
+
+  // The difference between starting values between each time interval.
+  let startingValueDelta;
+
+  // For any automation function that has an end or target value, the end value
+  // is based the starting value of the time interval.  The starting value will
+  // be increased or decreased by |startEndValueChange|. We choose half of
+  // |startingValueDelta| so that the ending value will be distinct from the
+  // starting value for next time interval.  This allows us to detect where the
+  // ramp begins and ends.
+  let startEndValueChange;
+
+  // Default threshold to use for detecting discontinuities that should appear
+  // at each time interval.
+  let discontinuityThreshold;
+
+  // Time interval between value changes.  It is best if 1 / numberOfTests is
+  // not close to timeInterval.
+  let timeIntervalInternal = .03;
+
+  let context;
+
+  // Make sure we render long enough to capture all of our test data.
+  function renderLength(numberOfTests) {
+    return timeToSampleFrame((numberOfTests + 1) * timeInterval, sampleRate);
+  }
+
+  // Create a constant reference signal with the given |value|.  Basically the
+  // same as |createConstantBuffer|, but with the parameters to match the other
+  // create functions.  The |endValue| is ignored.
+  function createConstantArray(
+      startTime, endTime, value, endValue, sampleRate) {
+    let startFrame = timeToSampleFrame(startTime, sampleRate);
+    let endFrame = timeToSampleFrame(endTime, sampleRate);
+    let length = endFrame - startFrame;
+
+    let buffer = createConstantBuffer(context, length, value);
+
+    return buffer.getChannelData(0);
+  }
+
+  function getStartEndFrames(startTime, endTime, sampleRate) {
+    // Start frame is the ceiling of the start time because the ramp starts at
+    // or after the sample frame.  End frame is the ceiling because it's the
+    // exclusive ending frame of the automation.
+    let startFrame = Math.ceil(startTime * sampleRate);
+    let endFrame = Math.ceil(endTime * sampleRate);
+
+    return {startFrame: startFrame, endFrame: endFrame};
+  }
+
+  // Create a linear ramp starting at |startValue| and ending at |endValue|. The
+  // ramp starts at time |startTime| and ends at |endTime|.  (The start and end
+  // times are only used to compute how many samples to return.)
+  function createLinearRampArray(
+      startTime, endTime, startValue, endValue, sampleRate) {
+    let frameInfo = getStartEndFrames(startTime, endTime, sampleRate);
+    let startFrame = frameInfo.startFrame;
+    let endFrame = frameInfo.endFrame;
+    let length = endFrame - startFrame;
+    let array = new Array(length);
+
+    let step = Math.fround(
+        (endValue - startValue) / (endTime - startTime) / sampleRate);
+    let start = Math.fround(
+        startValue +
+        (endValue - startValue) * (startFrame / sampleRate - startTime) /
+            (endTime - startTime));
+
+    let slope = (endValue - startValue) / (endTime - startTime);
+
+    // v(t) = v0 + (v1 - v0)*(t-t0)/(t1-t0)
+    for (k = 0; k < length; ++k) {
+      // array[k] = Math.fround(start + k * step);
+      let t = (startFrame + k) / sampleRate;
+      array[k] = startValue + slope * (t - startTime);
+    }
+
+    return array;
+  }
+
+  // Create an exponential ramp starting at |startValue| and ending at
+  // |endValue|. The ramp starts at time |startTime| and ends at |endTime|.
+  // (The start and end times are only used to compute how many samples to
+  // return.)
+  function createExponentialRampArray(
+      startTime, endTime, startValue, endValue, sampleRate) {
+    let deltaTime = endTime - startTime;
+
+    let frameInfo = getStartEndFrames(startTime, endTime, sampleRate);
+    let startFrame = frameInfo.startFrame;
+    let endFrame = frameInfo.endFrame;
+    let length = endFrame - startFrame;
+    let array = new Array(length);
+
+    let ratio = endValue / startValue;
+
+    // v(t) = v0*(v1/v0)^((t-t0)/(t1-t0))
+    for (let k = 0; k < length; ++k) {
+      let t = Math.fround((startFrame + k) / sampleRate);
+      array[k] = Math.fround(
+          startValue * Math.pow(ratio, (t - startTime) / deltaTime));
+    }
+
+    return array;
+  }
+
+  function discreteTimeConstantForSampleRate(timeConstant, sampleRate) {
+    return 1 - Math.exp(-1 / (sampleRate * timeConstant));
+  }
+
+  // Create a signal that starts at |startValue| and exponentially approaches
+  // the target value of |targetValue|, using a time constant of |timeConstant|.
+  // The ramp starts at time |startTime| and ends at |endTime|.  (The start and
+  // end times are only used to compute how many samples to return.)
+  function createExponentialApproachArray(
+      startTime, endTime, startValue, targetValue, sampleRate, timeConstant) {
+    let startFrameFloat = startTime * sampleRate;
+    let frameInfo = getStartEndFrames(startTime, endTime, sampleRate);
+    let startFrame = frameInfo.startFrame;
+    let endFrame = frameInfo.endFrame;
+    let length = Math.floor(endFrame - startFrame);
+    let array = new Array(length);
+    let c = discreteTimeConstantForSampleRate(timeConstant, sampleRate);
+
+    let delta = startValue - targetValue;
+
+    // v(t) = v1 + (v0 - v1) * exp(-(t-t0)/tau)
+    for (let k = 0; k < length; ++k) {
+      let t = (startFrame + k) / sampleRate;
+      let value =
+          targetValue + delta * Math.exp(-(t - startTime) / timeConstant);
+      array[k] = value;
+    }
+
+    return array;
+  }
+
+  // Create a sine wave of the specified duration.
+  function createReferenceSineArray(
+      startTime, endTime, startValue, endValue, sampleRate) {
+    // Ignore |startValue| and |endValue| for the sine wave.
+    let curve = createSineWaveArray(
+        endTime - startTime, freqHz, sineAmplitude, sampleRate);
+    // Sample the curve appropriately.
+    let frameInfo = getStartEndFrames(startTime, endTime, sampleRate);
+    let startFrame = frameInfo.startFrame;
+    let endFrame = frameInfo.endFrame;
+    let length = Math.floor(endFrame - startFrame);
+    let array = new Array(length);
+
+    // v(t) = linearly interpolate between V[k] and V[k + 1] where k =
+    // floor((N-1)/duration*(t - t0))
+    let f = (length - 1) / (endTime - startTime);
+
+    for (let k = 0; k < length; ++k) {
+      let t = (startFrame + k) / sampleRate;
+      let indexFloat = f * (t - startTime);
+      let index = Math.floor(indexFloat);
+      if (index + 1 < length) {
+        let v0 = curve[index];
+        let v1 = curve[index + 1];
+        array[k] = v0 + (v1 - v0) * (indexFloat - index);
+      } else {
+        array[k] = curve[length - 1];
+      }
+    }
+
+    return array;
+  }
+
+  // Create a sine wave of the given frequency and amplitude.  The sine wave is
+  // offset by half the amplitude so that result is always positive.
+  function createSineWaveArray(durationSeconds, freqHz, amplitude, sampleRate) {
+    let length = timeToSampleFrame(durationSeconds, sampleRate);
+    let signal = new Float32Array(length);
+    let omega = 2 * Math.PI * freqHz / sampleRate;
+    let halfAmplitude = amplitude / 2;
+
+    for (let k = 0; k < length; ++k) {
+      signal[k] = halfAmplitude + halfAmplitude * Math.sin(omega * k);
+    }
+
+    return signal;
+  }
+
+  // Return the difference between the starting value and the ending value for
+  // time interval |timeIntervalIndex|.  We alternate between an end value that
+  // is above or below the starting value.
+  function endValueDelta(timeIntervalIndex) {
+    if (timeIntervalIndex & 1) {
+      return -startEndValueChange;
+    } else {
+      return startEndValueChange;
+    }
+  }
+
+  // Relative error metric
+  function relativeErrorMetric(actual, expected) {
+    return (actual - expected) / Math.abs(expected);
+  }
+
+  // Difference metric
+  function differenceErrorMetric(actual, expected) {
+    return actual - expected;
+  }
+
+  // Return the difference between the starting value at |timeIntervalIndex| and
+  // the starting value at the next time interval.  Since we started at a large
+  // initial value, we decrease the value at each time interval.
+  function valueUpdate(timeIntervalIndex) {
+    return -startingValueDelta;
+  }
+
+  // Compare a section of the rendered data against our expected signal.
+  function comparePartialSignals(
+      should, rendered, expectedFunction, startTime, endTime, valueInfo,
+      sampleRate, errorMetric) {
+    let startSample = timeToSampleFrame(startTime, sampleRate);
+    let expected = expectedFunction(
+        startTime, endTime, valueInfo.startValue, valueInfo.endValue,
+        sampleRate, timeConstant);
+
+    let n = expected.length;
+    let maxError = -1;
+    let maxErrorIndex = -1;
+
+    for (let k = 0; k < n; ++k) {
+      // Make sure we don't pass these tests because a NaN has been generated in
+      // either the
+      // rendered data or the reference data.
+      if (!isValidNumber(rendered[startSample + k])) {
+        maxError = Infinity;
+        maxErrorIndex = startSample + k;
+        should(
+            isValidNumber(rendered[startSample + k]),
+            'NaN or infinity for rendered data at ' + maxErrorIndex)
+            .beTrue();
+        break;
+      }
+      if (!isValidNumber(expected[k])) {
+        maxError = Infinity;
+        maxErrorIndex = startSample + k;
+        should(
+            isValidNumber(expected[k]),
+            'NaN or infinity for rendered data at ' + maxErrorIndex)
+            .beTrue();
+        break;
+      }
+      let error = Math.abs(errorMetric(rendered[startSample + k], expected[k]));
+      if (error > maxError) {
+        maxError = error;
+        maxErrorIndex = k;
+      }
+    }
+
+    return {maxError: maxError, index: maxErrorIndex, expected: expected};
+  }
+
+  // Find the discontinuities in the data and compare the locations of the
+  // discontinuities with the times that define the time intervals. There is a
+  // discontinuity if the difference between successive samples exceeds the
+  // threshold.
+  function verifyDiscontinuities(should, values, times, threshold) {
+    let n = values.length;
+    let success = true;
+    let badLocations = 0;
+    let breaks = [];
+
+    // Find discontinuities.
+    for (let k = 1; k < n; ++k) {
+      if (Math.abs(values[k] - values[k - 1]) > threshold) {
+        breaks.push(k);
+      }
+    }
+
+    let testCount;
+
+    // If there are numberOfTests intervals, there are only numberOfTests - 1
+    // internal interval boundaries. Hence the maximum number of discontinuties
+    // we expect to find is numberOfTests - 1. If we find more than that, we
+    // have no reference to compare against. We also assume that the actual
+    // discontinuities are close to the expected ones.
+    //
+    // This is just a sanity check when something goes really wrong.  For
+    // example, if the threshold is too low, every sample frame looks like a
+    // discontinuity.
+    if (breaks.length >= numberOfTests) {
+      testCount = numberOfTests - 1;
+      should(breaks.length, 'Number of discontinuities')
+          .beLessThan(numberOfTests);
+      success = false;
+    } else {
+      testCount = breaks.length;
+    }
+
+    // Compare the location of each discontinuity with the end time of each
+    // interval. (There is no discontinuity at the start of the signal.)
+    for (let k = 0; k < testCount; ++k) {
+      let expectedSampleFrame = timeToSampleFrame(times[k + 1], sampleRate);
+      if (breaks[k] != expectedSampleFrame) {
+        success = false;
+        ++badLocations;
+        should(breaks[k], 'Discontinuity at index')
+            .beEqualTo(expectedSampleFrame);
+      }
+    }
+
+    if (badLocations) {
+      should(badLocations, 'Number of discontinuites at incorrect locations')
+          .beEqualTo(0);
+      success = false;
+    } else {
+      should(
+          breaks.length + 1,
+          'Number of tests started and ended at the correct time')
+          .beEqualTo(numberOfTests);
+    }
+
+    return success;
+  }
+
+  // Compare the rendered data with the expected data.
+  //
+  // testName - string describing the test
+  //
+  // maxError - maximum allowed difference between the rendered data and the
+  // expected data
+  //
+  // rendererdData - array containing the rendered (actual) data
+  //
+  // expectedFunction - function to compute the expected data
+  //
+  // timeValueInfo - array containing information about the start and end times
+  // and the start and end values of each interval.
+  //
+  // breakThreshold - threshold to use for determining discontinuities.
+  function compareSignals(
+      should, testName, maxError, renderedData, expectedFunction, timeValueInfo,
+      breakThreshold, errorMetric) {
+    let success = true;
+    let failedTestCount = 0;
+    let times = timeValueInfo.times;
+    let values = timeValueInfo.values;
+    let n = values.length;
+    let expectedSignal = [];
+
+    success =
+        verifyDiscontinuities(should, renderedData, times, breakThreshold);
+
+    for (let k = 0; k < n; ++k) {
+      let result = comparePartialSignals(
+          should, renderedData, expectedFunction, times[k], times[k + 1],
+          values[k], sampleRate, errorMetric);
+
+      expectedSignal =
+          expectedSignal.concat(Array.prototype.slice.call(result.expected));
+
+      should(
+          result.maxError,
+          'Max error for test ' + k + ' at offset ' +
+              (result.index + timeToSampleFrame(times[k], sampleRate)))
+          .beLessThanOrEqualTo(maxError);
+    }
+
+    should(
+        failedTestCount,
+        'Number of failed tests with an acceptable relative tolerance of ' +
+            maxError)
+        .beEqualTo(0);
+  }
+
+  // Create a function to test the rendered data with the reference data.
+  //
+  // testName - string describing the test
+  //
+  // error - max allowed error between rendered data and the reference data.
+  //
+  // referenceFunction - function that generates the reference data to be
+  // compared with the rendered data.
+  //
+  // jumpThreshold - optional parameter that specifies the threshold to use for
+  // detecting discontinuities.  If not specified, defaults to
+  // discontinuityThreshold.
+  //
+  function checkResultFunction(
+      task, should, testName, error, referenceFunction, jumpThreshold,
+      errorMetric) {
+    return function(event) {
+      let buffer = event.renderedBuffer;
+      renderedData = buffer.getChannelData(0);
+
+      let threshold;
+
+      if (!jumpThreshold) {
+        threshold = discontinuityThreshold;
+      } else {
+        threshold = jumpThreshold;
+      }
+
+      compareSignals(
+          should, testName, error, renderedData, referenceFunction,
+          timeValueInfo, threshold, errorMetric);
+      task.done();
+    }
+  }
+
+  // Run all the automation tests.
+  //
+  // numberOfTests - number of tests (time intervals) to run.
+  //
+  // initialValue - The initial value of the first time interval.
+  //
+  // setValueFunction - function that sets the specified value at the start of a
+  // time interval.
+  //
+  // automationFunction - function that sets the end value for the time
+  // interval. It specifies how the value approaches the end value.
+  //
+  // An object is returned containing an array of start times for each time
+  // interval, and an array giving the start and end values for the interval.
+  function doAutomation(
+      numberOfTests, initialValue, setValueFunction, automationFunction) {
+    let timeInfo = [0];
+    let valueInfo = [];
+    let value = initialValue;
+
+    for (let k = 0; k < numberOfTests; ++k) {
+      let startTime = k * timeInterval;
+      let endTime = (k + 1) * timeInterval;
+      let endValue = value + endValueDelta(k);
+
+      // Set the value at the start of the time interval.
+      setValueFunction(value, startTime);
+
+      // Specify the end or target value, and how we should approach it.
+      automationFunction(endValue, startTime, endTime);
+
+      // Keep track of the start times, and the start and end values for each
+      // time interval.
+      timeInfo.push(endTime);
+      valueInfo.push({startValue: value, endValue: endValue});
+
+      value += valueUpdate(k);
+    }
+
+    return {times: timeInfo, values: valueInfo};
+  }
+
+  // Create the audio graph for the test and then run the test.
+  //
+  // numberOfTests - number of time intervals (tests) to run.
+  //
+  // initialValue - the initial value of the gain at time 0.
+  //
+  // setValueFunction - function to set the value at the beginning of each time
+  // interval.
+  //
+  // automationFunction - the AudioParamTimeline automation function
+  //
+  // testName - string indicating the test that is being run.
+  //
+  // maxError - maximum allowed error between the rendered data and the
+  // reference data
+  //
+  // referenceFunction - function that generates the reference data to be
+  // compared against the rendered data.
+  //
+  // jumpThreshold - optional parameter that specifies the threshold to use for
+  // detecting discontinuities.  If not specified, defaults to
+  // discontinuityThreshold.
+  //
+  function createAudioGraphAndTest(
+      task, should, numberOfTests, initialValue, setValueFunction,
+      automationFunction, testName, maxError, referenceFunction, jumpThreshold,
+      errorMetric) {
+    // Create offline audio context.
+    context =
+        new OfflineAudioContext(2, renderLength(numberOfTests), sampleRate);
+    let constantBuffer =
+        createConstantBuffer(context, renderLength(numberOfTests), 1);
+
+    // We use an AudioGainNode here simply as a convenient way to test the
+    // AudioParam automation, since it's easy to pass a constant value through
+    // the node, automate the .gain attribute and observe the resulting values.
+
+    gainNode = context.createGain();
+
+    let bufferSource = context.createBufferSource();
+    bufferSource.buffer = constantBuffer;
+    bufferSource.connect(gainNode);
+    gainNode.connect(context.destination);
+
+    // Set up default values for the parameters that control how the automation
+    // test values progress for each time interval.
+    startingValueDelta = initialValue / numberOfTests;
+    startEndValueChange = startingValueDelta / 2;
+    discontinuityThreshold = startEndValueChange / 2;
+
+    // Run the automation tests.
+    timeValueInfo = doAutomation(
+        numberOfTests, initialValue, setValueFunction, automationFunction);
+    bufferSource.start(0);
+
+    context.oncomplete = checkResultFunction(
+        task, should, testName, maxError, referenceFunction, jumpThreshold,
+        errorMetric || relativeErrorMetric);
+    context.startRendering();
+  }
+
+  // Export local references to global scope. All the new objects in this file
+  // must be exported through this if it is to be used in the actual test HTML
+  // page.
+  let exports = {
+    'sampleRate': 44100,
+    'gainNode': null,
+    'timeInterval': timeIntervalInternal,
+
+    // Some suitable time constant so that we can see a significant change over
+    // a timeInterval.  This is only needed by setTargetAtTime() which needs a
+    // time constant.
+    'timeConstant': timeIntervalInternal / 3,
+
+    'renderLength': renderLength,
+    'createConstantArray': createConstantArray,
+    'getStartEndFrames': getStartEndFrames,
+    'createLinearRampArray': createLinearRampArray,
+    'createExponentialRampArray': createExponentialRampArray,
+    'discreteTimeConstantForSampleRate': discreteTimeConstantForSampleRate,
+    'createExponentialApproachArray': createExponentialApproachArray,
+    'createReferenceSineArray': createReferenceSineArray,
+    'createSineWaveArray': createSineWaveArray,
+    'endValueDelta': endValueDelta,
+    'relativeErrorMetric': relativeErrorMetric,
+    'differenceErrorMetric': differenceErrorMetric,
+    'valueUpdate': valueUpdate,
+    'comparePartialSignals': comparePartialSignals,
+    'verifyDiscontinuities': verifyDiscontinuities,
+    'compareSignals': compareSignals,
+    'checkResultFunction': checkResultFunction,
+    'doAutomation': doAutomation,
+    'createAudioGraphAndTest': createAudioGraphAndTest
+  };
+
+  for (let reference in exports) {
+    global[reference] = exports[reference];
+  }
+
+})(window);

tests/wpt/web-platform-tests/webaudio/resources/audit-util.js

@@ -0,0 +1,195 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+
+/**
+ * @fileOverview  This file includes legacy utility functions for the layout
+ *                test.
+ */
+
+// How many frames in a WebAudio render quantum.
+let RENDER_QUANTUM_FRAMES = 128;
+
+// Compare two arrays (commonly extracted from buffer.getChannelData()) with
+// constraints:
+//   options.thresholdSNR: Minimum allowed SNR between the actual and expected
+//     signal. The default value is 10000.
+//   options.thresholdDiffULP: Maximum allowed difference between the actual
+//     and expected signal in ULP(Unit in the last place). The default is 0.
+//   options.thresholdDiffCount: Maximum allowed number of sample differences
+//     which exceeds the threshold. The default is 0.
+//   options.bitDepth: The expected result is assumed to come from an audio
+//     file with this number of bits of precision. The default is 16.
+function compareBuffersWithConstraints(should, actual, expected, options) {
+  if (!options)
+    options = {};
+
+  // Only print out the message if the lengths are different; the
+  // expectation is that they are the same, so don't clutter up the
+  // output.
+  if (actual.length !== expected.length) {
+    should(
+        actual.length === expected.length,
+        'Length of actual and expected buffers should match')
+        .beTrue();
+  }
+
+  let maxError = -1;
+  let diffCount = 0;
+  let errorPosition = -1;
+  let thresholdSNR = (options.thresholdSNR || 10000);
+
+  let thresholdDiffULP = (options.thresholdDiffULP || 0);
+  let thresholdDiffCount = (options.thresholdDiffCount || 0);
+
+  // By default, the bit depth is 16.
+  let bitDepth = (options.bitDepth || 16);
+  let scaleFactor = Math.pow(2, bitDepth - 1);
+
+  let noisePower = 0, signalPower = 0;
+
+  for (let i = 0; i < actual.length; i++) {
+    let diff = actual[i] - expected[i];
+    noisePower += diff * diff;
+    signalPower += expected[i] * expected[i];
+
+    if (Math.abs(diff) > maxError) {
+      maxError = Math.abs(diff);
+      errorPosition = i;
+    }
+
+    // The reference file is a 16-bit WAV file, so we will almost never get
+    // an exact match between it and the actual floating-point result.
+    if (Math.abs(diff) > scaleFactor)
+      diffCount++;
+  }
+
+  let snr = 10 * Math.log10(signalPower / noisePower);
+  let maxErrorULP = maxError * scaleFactor;
+
+  should(snr, 'SNR').beGreaterThanOrEqualTo(thresholdSNR);
+
+  should(
+      maxErrorULP,
+      options.prefix + ': Maximum difference (in ulp units (' + bitDepth +
+          '-bits))')
+      .beLessThanOrEqualTo(thresholdDiffULP);
+
+  should(diffCount, options.prefix + ': Number of differences between results')
+      .beLessThanOrEqualTo(thresholdDiffCount);
+}
+
+// Create an impulse in a buffer of length sampleFrameLength
+function createImpulseBuffer(context, sampleFrameLength) {
+  let audioBuffer =
+      context.createBuffer(1, sampleFrameLength, context.sampleRate);
+  let n = audioBuffer.length;
+  let dataL = audioBuffer.getChannelData(0);
+
+  for (let k = 0; k < n; ++k) {
+    dataL[k] = 0;
+  }
+  dataL[0] = 1;
+
+  return audioBuffer;
+}
+
+// Create a buffer of the given length with a linear ramp having values 0 <= x <
+// 1.
+function createLinearRampBuffer(context, sampleFrameLength) {
+  let audioBuffer =
+      context.createBuffer(1, sampleFrameLength, context.sampleRate);
+  let n = audioBuffer.length;
+  let dataL = audioBuffer.getChannelData(0);
+
+  for (let i = 0; i < n; ++i)
+    dataL[i] = i / n;
+
+  return audioBuffer;
+}
+
+// Create an AudioBuffer of length |sampleFrameLength| having a constant value
+// |constantValue|. If |constantValue| is a number, the buffer has one channel
+// filled with that value. If |constantValue| is an array, the buffer is created
+// wit a number of channels equal to the length of the array, and channel k is
+// filled with the k'th element of the |constantValue| array.
+function createConstantBuffer(context, sampleFrameLength, constantValue) {
+  let channels;
+  let values;
+
+  if (typeof constantValue === 'number') {
+    channels = 1;
+    values = [constantValue];
+  } else {
+    channels = constantValue.length;
+    values = constantValue;
+  }
+
+  let audioBuffer =
+      context.createBuffer(channels, sampleFrameLength, context.sampleRate);
+  let n = audioBuffer.length;
+
+  for (let c = 0; c < channels; ++c) {
+    let data = audioBuffer.getChannelData(c);
+    for (let i = 0; i < n; ++i)
+      data[i] = values[c];
+  }
+
+  return audioBuffer;
+}
+
+// Create a stereo impulse in a buffer of length sampleFrameLength
+function createStereoImpulseBuffer(context, sampleFrameLength) {
+  let audioBuffer =
+      context.createBuffer(2, sampleFrameLength, context.sampleRate);
+  let n = audioBuffer.length;
+  let dataL = audioBuffer.getChannelData(0);
+  let dataR = audioBuffer.getChannelData(1);
+
+  for (let k = 0; k < n; ++k) {
+    dataL[k] = 0;
+    dataR[k] = 0;
+  }
+  dataL[0] = 1;
+  dataR[0] = 1;
+
+  return audioBuffer;
+}
+
+// Convert time (in seconds) to sample frames.
+function timeToSampleFrame(time, sampleRate) {
+  return Math.floor(0.5 + time * sampleRate);
+}
+
+// Compute the number of sample frames consumed by noteGrainOn with
+// the specified |grainOffset|, |duration|, and |sampleRate|.
+function grainLengthInSampleFrames(grainOffset, duration, sampleRate) {
+  let startFrame = timeToSampleFrame(grainOffset, sampleRate);
+  let endFrame = timeToSampleFrame(grainOffset + duration, sampleRate);
+
+  return endFrame - startFrame;
+}
+
+// True if the number is not an infinity or NaN
+function isValidNumber(x) {
+  return !isNaN(x) && (x != Infinity) && (x != -Infinity);
+}
+
+// Compute the (linear) signal-to-noise ratio between |actual| and
+// |expected|.  The result is NOT in dB!  If the |actual| and
+// |expected| have different lengths, the shorter length is used.
+function computeSNR(actual, expected) {
+  let signalPower = 0;
+  let noisePower = 0;
+
+  let length = Math.min(actual.length, expected.length);
+
+  for (let k = 0; k < length; ++k) {
+    let diff = actual[k] - expected[k];
+    signalPower += expected[k] * expected[k];
+    noisePower += diff * diff;
+  }
+
+  return signalPower / noisePower;
+}

tests/wpt/web-platform-tests/webaudio/resources/start-stop-exceptions.js

@@ -0,0 +1,45 @@
+// Test that exceptions are throw for invalid values for start and
+// stop.
+function testStartStop(should, node, options) {
+  // Test non-finite values for start.  These should all throw a TypeError
+  const nonFiniteValues = [NaN, Infinity, -Infinity];
+
+  nonFiniteValues.forEach(time => {
+      should(() => {
+        node.start(time);
+      }, `start(${time})`)
+    .throw('TypeError');
+    });
+
+  should(() => {
+    node.stop();
+  }, 'Calling stop() before start()').throw('InvalidStateError');
+
+  should(() => {
+    node.start(-1);
+  }, 'start(-1)').throw('RangeError');
+
+  if (options) {
+    options.forEach(test => {
+      should(() => {node.start(...test.args)},
+             'start(' + test.args + ')').throw(test.errorType);
+    });
+  }
+
+  node.start();
+  should(() => {
+    node.start();
+  }, 'Calling start() twice').throw('InvalidStateError');
+  should(() => {
+    node.stop(-1);
+  }, 'stop(-1)').throw('RangeError');
+
+  // Test non-finite stop times
+  nonFiniteValues.forEach(time => {
+      should(() => {
+        node.stop(time);
+      }, `stop(${time})`)
+    .throw('TypeError');
+    });
+}
+