juce_Limiter.cpp

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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>
void Limiter<SampleType>::setThreshold (SampleType newThreshold)
{
    thresholddB = newThreshold;
    update();
}
 
template <typename SampleType>
void Limiter<SampleType>::setRelease (SampleType newRelease)
{
    releaseTime = newRelease;
    update();
}
 
//==============================================================================
template <typename SampleType>
void Limiter<SampleType>::prepare (const ProcessSpec& spec)
{
    jassert (spec.sampleRate > 0);
    jassert (spec.numChannels > 0);
 
    sampleRate = spec.sampleRate;
 
    firstStageCompressor.prepare (spec);
    secondStageCompressor.prepare (spec);
 
    update();
    reset();
}
 
template <typename SampleType>
void Limiter<SampleType>::reset()
{
    firstStageCompressor.reset();
    secondStageCompressor.reset();
 
    outputVolume.reset (sampleRate, 0.001);
}
 
//==============================================================================
template <typename SampleType>
void Limiter<SampleType>::update()
{
    firstStageCompressor.setThreshold ((SampleType) -10.0);
    firstStageCompressor.setRatio     ((SampleType) 4.0);
    firstStageCompressor.setAttack    ((SampleType) 2.0);
    firstStageCompressor.setRelease   ((SampleType) 200.0);
 
    secondStageCompressor.setThreshold (thresholddB);
    secondStageCompressor.setRatio     ((SampleType) 1000.0);
    secondStageCompressor.setAttack    ((SampleType) 0.001);
    secondStageCompressor.setRelease   (releaseTime);
 
    auto ratioInverse = (SampleType) (1.0 / 4.0);
 
    auto gain = (SampleType) std::pow (10.0, 10.0 * (1.0 - ratioInverse) / 40.0);
    gain *= Decibels::decibelsToGain (-thresholddB, (SampleType) -100.0);
 
    outputVolume.setTargetValue (gain);
}
 
//==============================================================================
template class Limiter<float>;
template class Limiter<double>;
 
} // namespace juce::dsp