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 /*

  * Copyright (C) 2012 Google Inc. All rights reserved.

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  *     from this software without specific prior written permission.

  *

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 #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