equalizer.hpp

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#pragma once
 
#include "tabulasonora/effect_presets.hpp"
 
#include <span>
 
namespace ts {

class Equalizer {
public:
    static constexpr int flat_gain = 0x40;

    explicit Equalizer(const EffectPresets& presets) noexcept;

    [[nodiscard]] bool available() const noexcept { return presets_ != nullptr; }

    [[nodiscard]] bool is_flat() const noexcept
    {
        return low_gain_ == flat_gain && high_gain_ == flat_gain;
    }

    void set_low_frequency(int value) noexcept;
    void set_low_gain(int value) noexcept;
    void set_high_frequency(int value) noexcept;
    void set_high_gain(int value) noexcept;

    void reset() noexcept;

    void clear() noexcept;

    void process(std::span<float> left, std::span<float> right) noexcept;
 
private:
    struct State {
        double x1 = 0.0;
        double y1 = 0.0;
    };
 
    static double step(const EqBand& band, State& state, double input) noexcept;
 
    void refresh() noexcept;
 
    const EffectPresets* presets_ = nullptr;
 
    int low_frequency_ = 0;
    int low_gain_ = flat_gain;
    int high_frequency_ = 0;
    int high_gain_ = flat_gain;
 
    EqBand low_{};
    EqBand high_{};
 
    State low_left_;
    State low_right_;
    State high_left_;
    State high_right_;
};
 
} // namespace ts