JUCE/modules/juce_dsp/widgets/juce_Limiter.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 limiter with standard threshold and release time controls, featuring
    two compressors and a hard clipper at 0 dB.

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

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

    /** Sets the release time in milliseconds of the limiter.*/
    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;
        }

        firstStageCompressor.process (context);

        auto secondContext = ProcessContextReplacing<SampleType> (outputBlock);
        secondStageCompressor.process (secondContext);

        outputBlock.multiplyBy (outputVolume);

        for (size_t channel = 0; channel < numChannels; ++channel)
        {
            FloatVectorOperations::clip (outputBlock.getChannelPointer (channel), outputBlock.getChannelPointer (channel),
                                         (SampleType) -1.0, (SampleType) 1.0, (int) numSamples);
        }
    }

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

    //==============================================================================
    Compressor<SampleType> firstStageCompressor, secondStageCompressor;
    SmoothedValue<SampleType, ValueSmoothingTypes::Linear> outputVolume;

    double sampleRate = 44100.0;
    SampleType thresholddB = -10.0, releaseTime = 100.0;
};

} // namespace dsp
} // namespace juce