BiquadProcessor.cpp   [plain text]

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "BiquadProcessor.h"

#include "BiquadDSPKernel.h"

namespace WebCore {

BiquadProcessor::BiquadProcessor(FilterType type, double sampleRate, size_t numberOfChannels, bool autoInitialize)
    : AudioDSPKernelProcessor(sampleRate, numberOfChannels)
    , m_type(type)
    , m_parameter1(0)
    , m_parameter2(0)
    , m_parameter3(0)
    , m_filterCoefficientsDirty(true)
{
    double nyquist = 0.5 * this->sampleRate();
    
    switch (type) {
    // Highpass and lowpass share the same parameters and only differ in filter type.
    case LowPass2:
    case HighPass2:
        m_parameter1 = AudioParam::create("frequency", 350.0, 20.0, nyquist);
        m_parameter2 = AudioParam::create("resonance", 0.0, -20.0, 20.0);
        m_parameter3 = AudioParam::create("unused", 0.0, 0.0, 1.0);
        break;

    case Peaking:
        m_parameter1 = AudioParam::create("frequency", 2500.0, 20.0, nyquist);
        m_parameter2 = AudioParam::create("gain", 0.0, -20.0, 20.0);
        m_parameter3 = AudioParam::create("Q", 0.5, 0.0, 1000.0);
        break;
    case Allpass:
        m_parameter1 = AudioParam::create("frequency", 2500.0, 20.0, nyquist);
        m_parameter2 = AudioParam::create("Q", 0.5, 0.0, 1000.0);
        m_parameter3 = AudioParam::create("unused", 0.0, 0.0, 1.0);
        break;
    case LowShelf:
        m_parameter1 = AudioParam::create("frequency", 80.0, 20.0, nyquist);
        m_parameter2 = AudioParam::create("gain", 0.0, 0.0, 1.0);
        m_parameter3 = AudioParam::create("unused", 0.0, 0.0, 1.0);
        break;
    case HighShelf:
        m_parameter1 = AudioParam::create("frequency", 10000.0, 20.0, nyquist);
        m_parameter2 = AudioParam::create("gain", 0.0, 0.0, 1.0);
        m_parameter3 = AudioParam::create("unused", 0.0, 0.0, 1.0);
        break;
    }

    if (autoInitialize)
        initialize();
}

BiquadProcessor::~BiquadProcessor()
{
    if (isInitialized())
        uninitialize();
}

PassOwnPtr<AudioDSPKernel> BiquadProcessor::createKernel()
{
    return adoptPtr(new BiquadDSPKernel(this));
}

void BiquadProcessor::process(AudioBus* source, AudioBus* destination, size_t framesToProcess)
{
    if (!isInitialized()) {
        destination->zero();
        return;
    }
        
    // Deal with smoothing / de-zippering.  Start out assuming filter parameters are not changing.
    // The BiquadDSPKernel objects rely on this value to see if they need to re-compute their internal filter coefficients.
    m_filterCoefficientsDirty = false;
    
    if (m_hasJustReset) {
        // Snap to exact values first time after reset, then smooth for subsequent changes.
        m_parameter1->resetSmoothedValue();
        m_parameter2->resetSmoothedValue();
        m_parameter3->resetSmoothedValue();
        m_filterCoefficientsDirty = true;
        m_hasJustReset = false;
    } else {
        // Smooth all of the filter parameters.  If they haven't yet converged to their target value then mark coefficients as dirty.
        bool isStable1 = m_parameter1->smooth();
        bool isStable2 = m_parameter2->smooth();
        bool isStable3 = m_parameter3->smooth();
        if (!(isStable1 && isStable2 && isStable3))
            m_filterCoefficientsDirty = true;
    }
        
    // For each channel of our input, process using the corresponding BiquadDSPKernel into the output channel.
    for (unsigned i = 0; i < m_kernels.size(); ++i)
        m_kernels[i]->process(source->channel(i)->data(), destination->channel(i)->data(), framesToProcess);
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)