JUCE/modules/juce_dsp/widgets/juce_Compressor.cpp

/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   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
{
namespace dsp
{

//==============================================================================
template <typename SampleType>
Compressor<SampleType>::Compressor()
{
    update();
}

//==============================================================================
template <typename SampleType>
void Compressor<SampleType>::setThreshold (SampleType newThreshold)
{
    thresholddB = newThreshold;
    update();
}

template <typename SampleType>
void Compressor<SampleType>::setRatio (SampleType newRatio)
{
    jassert (newRatio >= static_cast<SampleType> (1.0));

    ratio = newRatio;
    update();
}

template <typename SampleType>
void Compressor<SampleType>::setAttack (SampleType newAttack)
{
    attackTime = newAttack;
    update();
}

template <typename SampleType>
void Compressor<SampleType>::setRelease (SampleType newRelease)
{
    releaseTime = newRelease;
    update();
}

//==============================================================================
template <typename SampleType>
void Compressor<SampleType>::prepare (const ProcessSpec& spec)
{
    jassert (spec.sampleRate > 0);
    jassert (spec.numChannels > 0);

    sampleRate = spec.sampleRate;

    envelopeFilter.prepare (spec);

    update();
    reset();
}

template <typename SampleType>
void Compressor<SampleType>::reset()
{
    envelopeFilter.reset();
}

//==============================================================================
template <typename SampleType>
SampleType Compressor<SampleType>::processSample (int channel, SampleType inputValue)
{
    // Rectifier
    auto env = jmax ((SampleType) 0.0, inputValue);

    // Ballistics filter
    env = envelopeFilter.processSample (channel, env);

    // VCA
    auto gain = (env < threshold) ? static_cast<SampleType> (1.0)
                                  : std::pow (env * thresholdInverse, ratioInverse - static_cast<SampleType> (1.0));

    // Output
    return gain * inputValue;
}

template <typename SampleType>
void Compressor<SampleType>::update()
{
    threshold = Decibels::decibelsToGain (thresholddB, static_cast<SampleType> (-200.0));
    thresholdInverse = static_cast<SampleType> (1.0) / threshold;
    ratioInverse     = static_cast<SampleType> (1.0) / ratio;

    envelopeFilter.setAttackTime (attackTime);
    envelopeFilter.setReleaseTime (releaseTime);
}

//==============================================================================
template class Compressor<float>;
template class Compressor<double>;

} // namespace dsp
} // namespace juce