diff -r 000000000000 -r 6474c204b198 content/media/webaudio/blink/PeriodicWave.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/media/webaudio/blink/PeriodicWave.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,311 @@
+/*
+ * Copyright (C) 2012 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "PeriodicWave.h"
+#include <algorithm>
+#include <cmath>
+#include "mozilla/FFTBlock.h"
+
+const unsigned PeriodicWaveSize = 4096; // This must be a power of two.
+const unsigned NumberOfRanges = 36; // There should be 3 * log2(PeriodicWaveSize) 1/3 octave ranges.
+const float CentsPerRange = 1200 / 3; // 1/3 Octave.
+
+using namespace mozilla;
+using mozilla::dom::OscillatorType;
+
+namespace WebCore {
+
+PeriodicWave* PeriodicWave::create(float sampleRate,
+                                   const float* real,
+                                   const float* imag,
+                                   size_t numberOfComponents)
+{
+    bool isGood = real && imag && numberOfComponents > 0 &&
+         numberOfComponents <= PeriodicWaveSize;
+    MOZ_ASSERT(isGood);
+    if (isGood) {
+        PeriodicWave* periodicWave = new PeriodicWave(sampleRate);
+        periodicWave->createBandLimitedTables(real, imag, numberOfComponents);
+        return periodicWave;
+    }
+    return 0;
+}
+
+PeriodicWave* PeriodicWave::createSine(float sampleRate)
+{
+      PeriodicWave* periodicWave = new PeriodicWave(sampleRate);
+          periodicWave->generateBasicWaveform(OscillatorType::Sine);
+              return periodicWave;
+}
+
+PeriodicWave* PeriodicWave::createSquare(float sampleRate)
+{
+      PeriodicWave* periodicWave = new PeriodicWave(sampleRate);
+          periodicWave->generateBasicWaveform(OscillatorType::Square);
+              return periodicWave;
+}
+
+PeriodicWave* PeriodicWave::createSawtooth(float sampleRate)
+{
+      PeriodicWave* periodicWave = new PeriodicWave(sampleRate);
+          periodicWave->generateBasicWaveform(OscillatorType::Sawtooth);
+              return periodicWave;
+}
+
+PeriodicWave* PeriodicWave::createTriangle(float sampleRate)
+{
+      PeriodicWave* periodicWave = new PeriodicWave(sampleRate);
+          periodicWave->generateBasicWaveform(OscillatorType::Triangle);
+              return periodicWave;
+}
+
+PeriodicWave::PeriodicWave(float sampleRate)
+    : m_sampleRate(sampleRate)
+    , m_periodicWaveSize(PeriodicWaveSize)
+    , m_numberOfRanges(NumberOfRanges)
+    , m_centsPerRange(CentsPerRange)
+{
+    float nyquist = 0.5 * m_sampleRate;
+    m_lowestFundamentalFrequency = nyquist / maxNumberOfPartials();
+    m_rateScale = m_periodicWaveSize / m_sampleRate;
+}
+
+size_t PeriodicWave::sizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
+{
+    size_t amount = aMallocSizeOf(this);
+
+    amount += m_bandLimitedTables.SizeOfExcludingThis(aMallocSizeOf);
+    for (size_t i = 0; i < m_bandLimitedTables.Length(); i++) {
+        if (m_bandLimitedTables[i]) {
+            amount += m_bandLimitedTables[i]->SizeOfIncludingThis(aMallocSizeOf);
+        }
+    }
+
+    return amount;
+}
+
+void PeriodicWave::waveDataForFundamentalFrequency(float fundamentalFrequency, float* &lowerWaveData, float* &higherWaveData, float& tableInterpolationFactor)
+{
+    // Negative frequencies are allowed, in which case we alias
+    // to the positive frequency.
+    fundamentalFrequency = fabsf(fundamentalFrequency);
+
+    // Calculate the pitch range.
+    float ratio = fundamentalFrequency > 0 ? fundamentalFrequency / m_lowestFundamentalFrequency : 0.5;
+    float centsAboveLowestFrequency = logf(ratio)/logf(2.0f) * 1200;
+
+    // Add one to round-up to the next range just in time to truncate
+    // partials before aliasing occurs.
+    float pitchRange = 1 + centsAboveLowestFrequency / m_centsPerRange;
+
+    pitchRange = std::max(pitchRange, 0.0f);
+    pitchRange = std::min(pitchRange, static_cast<float>(m_numberOfRanges - 1));
+
+    // The words "lower" and "higher" refer to the table data having
+    // the lower and higher numbers of partials. It's a little confusing
+    // since the range index gets larger the more partials we cull out.
+    // So the lower table data will have a larger range index.
+    unsigned rangeIndex1 = static_cast<unsigned>(pitchRange);
+    unsigned rangeIndex2 = rangeIndex1 < m_numberOfRanges - 1 ? rangeIndex1 + 1 : rangeIndex1;
+
+    lowerWaveData = m_bandLimitedTables[rangeIndex2]->Elements();
+    higherWaveData = m_bandLimitedTables[rangeIndex1]->Elements();
+
+    // Ranges from 0 -> 1 to interpolate between lower -> higher.
+    tableInterpolationFactor = pitchRange - rangeIndex1;
+}
+
+unsigned PeriodicWave::maxNumberOfPartials() const
+{
+    return m_periodicWaveSize / 2;
+}
+
+unsigned PeriodicWave::numberOfPartialsForRange(unsigned rangeIndex) const
+{
+    // Number of cents below nyquist where we cull partials.
+    float centsToCull = rangeIndex * m_centsPerRange;
+
+    // A value from 0 -> 1 representing what fraction of the partials to keep.
+    float cullingScale = pow(2, -centsToCull / 1200);
+
+    // The very top range will have all the partials culled.
+    unsigned numberOfPartials = cullingScale * maxNumberOfPartials();
+
+    return numberOfPartials;
+}
+
+// Convert into time-domain wave buffers.
+// One table is created for each range for non-aliasing playback
+// at different playback rates. Thus, higher ranges have more
+// high-frequency partials culled out.
+void PeriodicWave::createBandLimitedTables(const float* realData, const float* imagData, unsigned numberOfComponents)
+{
+    float normalizationScale = 1;
+
+    unsigned fftSize = m_periodicWaveSize;
+    unsigned halfSize = fftSize / 2 + 1;
+    unsigned i;
+
+    numberOfComponents = std::min(numberOfComponents, halfSize);
+
+    m_bandLimitedTables.SetCapacity(m_numberOfRanges);
+
+    for (unsigned rangeIndex = 0; rangeIndex < m_numberOfRanges; ++rangeIndex) {
+        // This FFTBlock is used to cull partials (represented by frequency bins).
+        FFTBlock frame(fftSize);
+        nsAutoArrayPtr<float> realP(new float[halfSize]);
+        nsAutoArrayPtr<float> imagP(new float[halfSize]);
+
+        // Copy from loaded frequency data and scale.
+        float scale = fftSize;
+        AudioBufferCopyWithScale(realData, scale, realP, numberOfComponents);
+        AudioBufferCopyWithScale(imagData, scale, imagP, numberOfComponents);
+
+        // If fewer components were provided than 1/2 FFT size,
+        // then clear the remaining bins.
+        for (i = numberOfComponents; i < halfSize; ++i) {
+            realP[i] = 0;
+            imagP[i] = 0;
+        }
+
+        // Generate complex conjugate because of the way the
+        // inverse FFT is defined.
+        float minusOne = -1;
+        AudioBufferInPlaceScale(imagP, minusOne, halfSize);
+
+        // Find the starting bin where we should start culling.
+        // We need to clear out the highest frequencies to band-limit
+        // the waveform.
+        unsigned numberOfPartials = numberOfPartialsForRange(rangeIndex);
+
+        // Cull the aliasing partials for this pitch range.
+        for (i = numberOfPartials + 1; i < halfSize; ++i) {
+            realP[i] = 0;
+            imagP[i] = 0;
+        }
+        // Clear nyquist if necessary.
+        if (numberOfPartials < halfSize)
+            realP[halfSize-1] = 0;
+
+        // Clear any DC-offset.
+        realP[0] = 0;
+
+        // Clear values which have no effect.
+        imagP[0] = 0;
+        imagP[halfSize-1] = 0;
+
+        // Create the band-limited table.
+        AudioFloatArray* table = new AudioFloatArray(m_periodicWaveSize);
+        m_bandLimitedTables.AppendElement(table);
+
+        // Apply an inverse FFT to generate the time-domain table data.
+        float* data = m_bandLimitedTables[rangeIndex]->Elements();
+        frame.PerformInverseFFT(realP, imagP, data);
+
+        // For the first range (which has the highest power), calculate
+        // its peak value then compute normalization scale.
+        if (!rangeIndex) {
+            float maxValue;
+            maxValue = AudioBufferPeakValue(data, m_periodicWaveSize);
+
+            if (maxValue)
+                normalizationScale = 1.0f / maxValue;
+        }
+
+        // Apply normalization scale.
+        AudioBufferInPlaceScale(data, normalizationScale, m_periodicWaveSize);
+    }
+}
+
+void PeriodicWave::generateBasicWaveform(OscillatorType shape)
+{
+    const float piFloat = M_PI;
+    unsigned fftSize = periodicWaveSize();
+    unsigned halfSize = fftSize / 2 + 1;
+
+    AudioFloatArray real(halfSize);
+    AudioFloatArray imag(halfSize);
+    float* realP = real.Elements();
+    float* imagP = imag.Elements();
+
+    // Clear DC and Nyquist.
+    realP[0] = 0;
+    imagP[0] = 0;
+    realP[halfSize-1] = 0;
+    imagP[halfSize-1] = 0;
+
+    for (unsigned n = 1; n < halfSize; ++n) {
+        float omega = 2 * piFloat * n;
+        float invOmega = 1 / omega;
+
+        // Fourier coefficients according to standard definition.
+        float a; // Coefficient for cos().
+        float b; // Coefficient for sin().
+
+        // Calculate Fourier coefficients depending on the shape.
+        // Note that the overall scaling (magnitude) of the waveforms
+        // is normalized in createBandLimitedTables().
+        switch (shape) {
+        case OscillatorType::Sine:
+            // Standard sine wave function.
+            a = 0;
+            b = (n == 1) ? 1 : 0;
+            break;
+        case OscillatorType::Square:
+            // Square-shaped waveform with the first half its maximum value
+            // and the second half its minimum value.
+            a = 0;
+            b = invOmega * ((n & 1) ? 2 : 0);
+            break;
+        case OscillatorType::Sawtooth:
+            // Sawtooth-shaped waveform with the first half ramping from
+            // zero to maximum and the second half from minimum to zero.
+            a = 0;
+            b = -invOmega * cos(0.5 * omega);
+            break;
+        case OscillatorType::Triangle:
+            // Triangle-shaped waveform going from its maximum value to
+            // its minimum value then back to the maximum value.
+            a = (4 - 4 * cos(0.5 * omega)) / (n * n * piFloat * piFloat);
+            b = 0;
+            break;
+        default:
+            NS_NOTREACHED("invalid oscillator type");
+            a = 0;
+            b = 0;
+            break;
+        }
+
+        realP[n] = a;
+        imagP[n] = b;
+    }
+
+    createBandLimitedTables(realP, imagP, halfSize);
+}
+
+} // namespace WebCore