juce_Phaser.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy
 
   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce::dsp
{
 
template <typename SampleType>
class Phaser
{
public:
    //==============================================================================
    Phaser();
 
    //==============================================================================
    void setRate (SampleType newRateHz);
 
    void setDepth (SampleType newDepth);
 
    void setCentreFrequency (SampleType newCentreHz);
 
    void setFeedback (SampleType newFeedback);
 
    void setMix (SampleType newMix);
 
    //==============================================================================
    void prepare (const ProcessSpec& spec);
 
    void reset();
 
    //==============================================================================
    template <typename ProcessContext>
    void process (const ProcessContext& context) noexcept
    {
        const auto& inputBlock = context.getInputBlock();
        auto& outputBlock      = context.getOutputBlock();
        const auto numChannels = outputBlock.getNumChannels();
        const auto numSamples  = outputBlock.getNumSamples();
 
        jassert (inputBlock.getNumChannels() == numChannels);
        jassert (inputBlock.getNumChannels() == lastOutput.size());
        jassert (inputBlock.getNumSamples()  == numSamples);
 
        if (context.isBypassed)
        {
            outputBlock.copyFrom (inputBlock);
            return;
        }
 
        int numSamplesDown = 0;
        auto counter = updateCounter;
 
        for (size_t i = 0; i < numSamples; ++i)
        {
            if (counter == 0)
                numSamplesDown++;
 
            counter++;
 
            if (counter == maxUpdateCounter)
                counter = 0;
        }
 
        if (numSamplesDown > 0)
        {
            auto freqBlock = AudioBlock<SampleType> (bufferFrequency).getSubBlock (0, (size_t) numSamplesDown);
            auto contextFreq = ProcessContextReplacing<SampleType> (freqBlock);
            freqBlock.clear();
 
            osc.process (contextFreq);
            freqBlock.multiplyBy (oscVolume);
        }
 
        auto* freqSamples = bufferFrequency.getWritePointer (0);
 
        for (int i = 0; i < numSamplesDown; ++i)
        {
            auto lfo = jlimit (static_cast<SampleType> (0.0),
                               static_cast<SampleType> (1.0),
                               freqSamples[i] + normCentreFrequency);
 
            freqSamples[i] = mapToLog10 (lfo, static_cast<SampleType> (20.0),
                                         static_cast<SampleType> (jmin (20000.0, 0.49 * sampleRate)));
        }
 
        auto currentFrequency = filters[0]->getCutoffFrequency();
        dryWet.pushDrySamples (inputBlock);
 
        for (size_t channel = 0; channel < numChannels; ++channel)
        {
            counter = updateCounter;
            int k = 0;
 
            auto* inputSamples  = inputBlock .getChannelPointer (channel);
            auto* outputSamples = outputBlock.getChannelPointer (channel);
 
            for (size_t i = 0; i < numSamples; ++i)
            {
                auto input = inputSamples[i];
                auto output = input - lastOutput[channel];
 
                if (i == 0 && counter != 0)
                    for (int n = 0; n < numStages; ++n)
                        filters[n]->setCutoffFrequency (currentFrequency);
 
                if (counter == 0)
                {
                    for (int n = 0; n < numStages; ++n)
                        filters[n]->setCutoffFrequency (freqSamples[k]);
 
                    k++;
                }
 
                for (int n = 0; n < numStages; ++n)
                    output = filters[n]->processSample ((int) channel, output);
 
                outputSamples[i] = output;
                lastOutput[channel] = output * feedbackVolume[channel].getNextValue();
 
                counter++;
 
                if (counter == maxUpdateCounter)
                    counter = 0;
            }
        }
 
        dryWet.mixWetSamples (outputBlock);
        updateCounter = (updateCounter + (int) numSamples) % maxUpdateCounter;
    }
 
private:
    //==============================================================================
    void update();
 
    //==============================================================================
    Oscillator<SampleType> osc;
    OwnedArray<FirstOrderTPTFilter<SampleType>> filters;
    SmoothedValue<SampleType, ValueSmoothingTypes::Linear> oscVolume;
    std::vector<SmoothedValue<SampleType, ValueSmoothingTypes::Linear>> feedbackVolume { 2 };
    DryWetMixer<SampleType> dryWet;
    std::vector<SampleType> lastOutput { 2 };
    AudioBuffer<SampleType> bufferFrequency;
    SampleType normCentreFrequency = 0.5;
    double sampleRate = 44100.0;
 
    int updateCounter = 0;
    static constexpr int maxUpdateCounter = 4;
 
    SampleType rate = 1.0, depth = 0.5, feedback = 0.0, mix = 0.5;
    SampleType centreFrequency = 1300.0;
    static constexpr int numStages = 6;
};
 
} // namespace juce::dsp