JUCE/modules/juce_dsp/processors/juce_Panner.h

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

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

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

   For the technical preview this file cannot be licensed commercially.

   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
{

enum class PannerRule
{
    linear,          // regular 6 dB or linear panning rule, allows the panned sound to be
                     // perceived as having a constant level when summed to mono
    balanced,        // both left and right are 1 when pan value is 0, with left decreasing
                     // to 0 above this value and right decreasing to 0 below it
    sin3dB,          // alternate version of the regular 3 dB panning rule with a sine curve
    sin4p5dB,        // alternate version of the regular 4.5 dB panning rule with a sine curve
    sin6dB,          // alternate version of the regular 6 dB panning rule with a sine curve
    squareRoot3dB,   // regular 3 dB or constant power panning rule, allows the panned sound
                     // to be perceived as having a constant level regardless of the pan position
    squareRoot4p5dB  // regular 4.5 dB panning rule, a compromise option between 3 dB and 6 dB panning rules
};

/**
    A processor to perform panning operations on stereo buffers.

    @tags{DSP}
*/
template <typename SampleType>
class Panner
{
public:
    //==============================================================================
    using Rule = PannerRule;

    //==============================================================================
    /** Constructor. */
    Panner();

    //==============================================================================
    /** Sets the panning rule. */
    void setRule (Rule newRule);

    /** Sets the current panning value, between -1 (full left) and 1 (full right). */
    void setPan (SampleType newPan);

    //==============================================================================
    /** 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 numInputChannels  = inputBlock.getNumChannels();
        const auto numOutputChannels = outputBlock.getNumChannels();
        const auto numSamples        = outputBlock.getNumSamples();

        jassertquiet (inputBlock.getNumSamples() == numSamples);

        if (numOutputChannels != 2 || numInputChannels == 0 || numInputChannels > 2)
            return;

        if (numInputChannels == 2)
        {
            outputBlock.copyFrom (inputBlock);
        }
        else
        {
            outputBlock.getSingleChannelBlock (0).copyFrom (inputBlock);
            outputBlock.getSingleChannelBlock (1).copyFrom (inputBlock);
        }

        if (context.isBypassed)
            return;

        outputBlock.getSingleChannelBlock (0).multiplyBy (leftVolume);
        outputBlock.getSingleChannelBlock (1).multiplyBy (rightVolume);
    }

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

    //==============================================================================
    Rule currentRule = Rule::balanced;
    SampleType pan = 0.0;
    SmoothedValue<SampleType> leftVolume, rightVolume;
    double sampleRate = 44100.0;
};

} // namespace dsp
} // namespace juce