juce_BallisticsFilter.cpp

/*
  ==============================================================================
 
   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>
BallisticsFilter<SampleType>::BallisticsFilter()
{
    setAttackTime (attackTime);
    setReleaseTime (releaseTime);
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::setAttackTime (SampleType attackTimeMs)
{
    attackTime = attackTimeMs;
    cteAT = calculateLimitedCte (static_cast<SampleType> (attackTime));
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::setReleaseTime (SampleType releaseTimeMs)
{
    releaseTime = releaseTimeMs;
    cteRL = calculateLimitedCte (static_cast<SampleType> (releaseTime));
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::setLevelCalculationType (LevelCalculationType newLevelType)
{
    levelType = newLevelType;
    reset();
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::prepare (const ProcessSpec& spec)
{
    jassert (spec.sampleRate > 0);
    jassert (spec.numChannels > 0);
 
    sampleRate = spec.sampleRate;
    expFactor  = -2.0 * MathConstants<double>::pi * 1000.0 / sampleRate;
 
    setAttackTime  (attackTime);
    setReleaseTime (releaseTime);
 
    yold.resize (spec.numChannels);
 
    reset();
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::reset()
{
    reset (0);
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::reset (SampleType initialValue)
{
    for (auto& old : yold)
        old = initialValue;
}
 
template <typename SampleType>
SampleType BallisticsFilter<SampleType>::processSample (int channel, SampleType inputValue)
{
    jassert (isPositiveAndBelow (channel, yold.size()));
 
    if (levelType == LevelCalculationType::RMS)
        inputValue *= inputValue;
    else
        inputValue = std::abs (inputValue);
 
    SampleType cte = (inputValue > yold[(size_t) channel] ? cteAT : cteRL);
 
    SampleType result = inputValue + cte * (yold[(size_t) channel] - inputValue);
    yold[(size_t) channel] = result;
 
    if (levelType == LevelCalculationType::RMS)
        return std::sqrt (result);
 
    return result;
}
 
template <typename SampleType>
void BallisticsFilter<SampleType>::snapToZero() noexcept
{
    for (auto& old : yold)
        util::snapToZero (old);
}
 
template <typename SampleType>
SampleType BallisticsFilter<SampleType>::calculateLimitedCte (SampleType timeMs) const noexcept
{
    return timeMs < static_cast<SampleType> (1.0e-3) ? 0
                                                     : static_cast<SampleType> (std::exp (expFactor / timeMs));
}
 
//==============================================================================
template class BallisticsFilter<float>;
template class BallisticsFilter<double>;
 
} // namespace juce::dsp