mutable.hpp

// Copyright 2023 Katherine Whitlock
// Copyright 2014 Emilie Gillet
// Reverb.
 
#pragma once
#include "definitions_cxx.hpp"
#include "dsp/reverb/base.hpp"
#include "dsp/util.hpp"
#include "fx_engine.hpp"
#include <array>
#include <limits>
 
namespace deluge::dsp::reverb {
 
class Mutable : public Base {
    constexpr static size_t kBufferSize = 32768;
 
public:
    Mutable() = default;
 
    ~Mutable() override = default;
 
    void process(std::span<int32_t> in, std::span<StereoSample> output) override {
        // This is the Griesinger topology described in the Dattorro paper
        // (4 AP diffusers on the input, then a loop of 2x 2AP+1Delay).
        // Modulation is applied to the two long delays for a slow shimmer/chorus effect.
        // Upstream also smears the first diffuser AP; that is deliberately not ported.
        typename FxEngine::AllPass ap1(150);
        typename FxEngine::AllPass ap2(214);
        typename FxEngine::AllPass ap3(319);
        typename FxEngine::AllPass ap4(527);
 
        typename FxEngine::AllPass dap1a(2182);
        typename FxEngine::AllPass dap1b(2690);
        typename FxEngine::AllPass del1(4501);
 
        typename FxEngine::AllPass dap2a(2525);
        typename FxEngine::AllPass dap2b(2197);
        typename FxEngine::AllPass del2(6312);
 
        typename FxEngine::Context c;
        FxEngine::ConstructTopology(engine_, //<
                                    {
                                        &ap1, &ap2, &ap3, &ap4, //<
                                        &dap1a, &dap1b, &del1,  //<
                                        &dap2a, &dap2b, &del2,  //<
                                    });
 
        const float kap = diffusion_;
        const float klp = lp_;
        const float krt = reverb_time_;
 
        float lp_1 = lp_decay_1_;
        float lp_2 = lp_decay_2_;
 
        for (size_t frame = 0; frame < in.size(); frame++) {
            StereoSample& s = output[frame];
            float wet = 0;
            float apout = 0.0f;
            engine_.Advance();
 
            // Smear AP1 inside the loop.
            // c.Interpolate(ap1, 10.0f, LFO_1, 80.0f, 1.0f);
            // c.Write(ap1, 100, 0.0f);
 
            const float input_sample = in[frame] / static_cast<float>(std::numeric_limits<int32_t>::max());
 
            c.Set(input_sample);
 
            // Diffuse through 4 allpasses.
            ap1.Process(c, kap);
            ap2.Process(c, kap);
            ap3.Process(c, kap);
            ap4.Process(c, kap);
            apout = c.Get();
 
            // Main reverb loop.
            c.Set(apout);
            del2.Interpolate(c, 6261.0f, LFO_2, 50.0f, krt);
            c.Lp(lp_1, klp);
            dap1a.Process(c, -kap);
            dap1b.Process(c, kap);
            del1.Write(c, 2.0f);
            wet = c.Get();
            wet = wet - dsp::OnePole(hp_r_, wet, hp_cutoff_);
            wet = dsp::OnePole(lp_r_, wet, lp_cutoff_);
 
            auto output_right = dsp::toQ31Saturating(wet * kOutputGain);
 
            c.Set(apout);
            del1.Interpolate(c, 4460.0f, LFO_1, 40.0f, krt);
            c.Lp(lp_2, klp);
            dap2a.Process(c, -kap);
            dap2b.Process(c, kap);
            del2.Write(c, 2.0f);
            wet = c.Get();
            wet = wet - dsp::OnePole(hp_l_, wet, hp_cutoff_);
            wet = dsp::OnePole(lp_l_, wet, lp_cutoff_);
 
            auto output_left = dsp::toQ31Saturating(wet * kOutputGain);
 
            // Mix
            s.l += multiply_32x32_rshift32_rounded(output_left, getPanLeft());
            s.r += multiply_32x32_rshift32_rounded(output_right, getPanRight());
        }
 
        lp_decay_1_ = lp_1;
        lp_decay_2_ = lp_2;
    }
 
    inline void Clear() { engine_.Clear(); }

    static constexpr float kOutputGain = 15.f * 4294967296.f;
 
    static constexpr float kReverbTimeMin = 0.01f;
    static constexpr float kReverbTimeMax = 0.98f;
    static constexpr float kWidthMin = 0.1f;
    static constexpr float kWidthMax = 0.9f;
    static constexpr float kLpMin = 0.01f;
    static constexpr float kLpMax = 1.f;
 
    // Reverb Base Overrides
    void setRoomSize(float value) override {
        reverb_time_ = util::map(value, 0.f, 1.f, kReverbTimeMin, kReverbTimeMax);
    }
    [[nodiscard]] float getRoomSize() const override {
        return util::map(reverb_time_, kReverbTimeMin, kReverbTimeMax, 0.f, 1.f);
    };

    void setDamping(float value) override {
        lp_val_ = value;
        const float damping = std::clamp(std::log2((value * 50.f) + 1.f) / 5.7f, 0.f, 1.f);
        lp_ = util::map(1.f - damping, 0.f, 1.f, kLpMin, kLpMax);
    }
    [[nodiscard]] float getDamping() const override { return lp_val_; }
 
    void setWidth(float value) override { diffusion_ = util::map(value, 0.f, 1.f, kWidthMin, kWidthMax); }
    [[nodiscard]] float getWidth() const override { return util::map(diffusion_, kWidthMin, kWidthMax, 0.f, 1.f); };
 
    void setHPF(float f) override {
        hp_cutoff_val_ = f;
        hp_cutoff_ = calcFilterCutoff<FilterType::HighPass>(f);
    }
 
    [[nodiscard]] float getHPF() const override { return hp_cutoff_val_; }
 
    void setLPF(float f) override {
        lp_cutoff_val_ = f;
        lp_cutoff_ = calcFilterCutoff<FilterType::LowPass>(f);
    }
 
    [[nodiscard]] float getLPF() const override { return lp_cutoff_val_; }
 
protected:
    static constexpr float sample_rate = kSampleRate;
 
    std::array<float, kBufferSize> buffer_{};
    FxEngine engine_{buffer_, {0.5f / sample_rate, 0.3f / sample_rate}};
 
    // size
    float reverb_time_ = 0.665f;
 
    // width
    float diffusion_ = 0.625f;
 
    // damping
    float lp_{0.7f};
    float lp_val_{0.7f};
 
    // These are the state variables for the low-pass filters
    float lp_decay_1_{0};
    float lp_decay_2_{0};
 
    // High-pass
    float hp_cutoff_val_{0.f};
    // corresponds to 20Hz
    float hp_cutoff_{calcFilterCutoff<FilterType::HighPass>(0)};
    float hp_l_{0.0}; // HP state variable
    float hp_r_{0.0}; // HP state variable
 
    // Low-pass
    float lp_cutoff_val_{0.f};
    // corresponds to 0Hz
    float lp_cutoff_{calcFilterCutoff<FilterType::LowPass>(0)};
    float lp_l_{0.0}; // LP state variable
    float lp_r_{0.0}; // LP state variable
};
 
} // namespace deluge::dsp::reverb