JUCE/modules/juce_dsp/widgets/juce_NoiseGate.h

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

   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
{

/**
    A simple noise gate with standard threshold, ratio, attack time and
    release time controls. Can be used as an expander if the ratio is low.

    @tags{DSP}
*/
template <typename SampleType>
class NoiseGate
{
public:
    //==============================================================================
    /** Constructor. */
    NoiseGate();

    //==============================================================================
    /** Sets the threshold in dB of the noise-gate.*/
    void setThreshold (SampleType newThreshold);

    /** Sets the ratio of the noise-gate (must be higher or equal to 1).*/
    void setRatio (SampleType newRatio);

    /** Sets the attack time in milliseconds of the noise-gate.*/
    void setAttack (SampleType newAttack);

    /** Sets the release time in milliseconds of the noise-gate.*/
    void setRelease (SampleType newRelease);

    //==============================================================================
    /** Initialises the processor. */
    void prepare (const ProcessSpec& spec);

    /** Resets the internal state variables of the processor. */
    void reset();

    //==============================================================================
    /** Processes the input and output samples supplied in the processing context. */
    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.getNumSamples() == numSamples);

        if (context.isBypassed)
        {
            outputBlock.copyFrom (inputBlock);
            return;
        }

        for (size_t channel = 0; channel < numChannels; ++channel)
        {
            auto* inputSamples  = inputBlock .getChannelPointer (channel);
            auto* outputSamples = outputBlock.getChannelPointer (channel);

            for (size_t i = 0; i < numSamples; ++i)
                outputSamples[i] = processSample ((int) channel, inputSamples[i]);
        }
    }

    /** Performs the processing operation on a single sample at a time. */
    SampleType processSample (int channel, SampleType inputValue);

private:
    //==============================================================================
    void update();

    //==============================================================================
    SampleType threshold, thresholdInverse, currentRatio;
    BallisticsFilter<SampleType> envelopeFilter, RMSFilter;

    double sampleRate = 44100.0;
    SampleType thresholddB = -100, ratio = 10.0, attackTime = 1.0, releaseTime = 100.0;
};

} // namespace dsp
} // namespace juce