marvin_Biquad.h

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// ========================================================================================================
//  _______ _______ ______ ___ ___ _______ _______
// |   |   |   _   |   __ \   |   |_     _|    |  |
// |       |       |      <   |   |_|   |_|       |
// |__|_|__|___|___|___|__|\_____/|_______|__|____|
//
// This file is part of the Marvin open source library and is licensed under the terms of the MIT License.
//
// ========================================================================================================
 
#ifndef MARVIN_BIQUAD_H
#define MARVIN_BIQUAD_H
#include "marvin/library/marvin_Concepts.h"
#include "marvin/library/marvin_Literals.h"
#include "marvin/dsp/filters/biquad/marvin_BiquadCoefficients.h"
#include <array>
#include <cmath>
#include <cassert>
namespace marvin::dsp::filters {
    template <FloatType SampleType, size_t NumStages>
    class Biquad final {
    public:
        void setCoeffs(size_t stage, BiquadCoefficients<SampleType> coeffs) noexcept {
            m_coeffs[stage] = coeffs;
        }

        [[nodiscard]] SampleType operator()(SampleType x) noexcept {
            for (auto stage = 0_sz; stage < NumStages; ++stage) {
                const auto [a0, a1, a2, b0, b1, b2] = m_coeffs[stage];
                auto& delay = m_delays[stage];
                const auto y = static_cast<SampleType>(1.0) / b0 * ((a0 * x) + (a1 * delay.x_z1) + (a2 * delay.x_z2) - (b1 * delay.y_z1) - (b2 * delay.y_z2));
                delay(x, y);
                x = y;
            }
            return x;
        }

        void reset() noexcept {
            for (auto& d : m_delays) {
                d.reset();
            }
        }
 
    private:
        struct BiquadDelay final {
            SampleType x_z1{ static_cast<SampleType>(0.0) }, x_z2{ static_cast<SampleType>(0.0) };
            SampleType y_z1{ static_cast<SampleType>(0.0) }, y_z2{ static_cast<SampleType>(0.0) };
 
            void operator()(SampleType x, SampleType y) noexcept {
                x_z2 = x_z1;
                x_z1 = x;
                y_z2 = y_z1;
                y_z1 = y;
            }
 
            void reset() noexcept {
                x_z1 = x_z2 = y_z1 = y_z2 = static_cast<SampleType>(0.0);
            }
        };
        std::array<BiquadDelay, NumStages> m_delays;
        std::array<BiquadCoefficients<SampleType>, NumStages> m_coeffs;
    };
 
} // namespace marvin::dsp::filters
#endif