asymmetric_shaper.hpp

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// sbl/dsp/asymmetric_shaper.hpp — Asymmetric distortion primitive
//
// Adds even-order harmonics via a quadratic term: y = x + k * x²
//
// k controls the asymmetry:
//   k = 0.0: linear (no distortion)
//   k = 0.1: mild warmth (subtle 2nd harmonic)
//   k = 0.3+: obvious asymmetric character
//
// Asymmetric saturation is what gives tube and transformer coloration
// its "warm" quality — the positive and negative half-cycles are shaped
// differently, introducing even-order harmonics (2nd, 4th) that the ear
// perceives as warmth rather than harshness.
//
// This primitive exposes the asymmetry amount as a configurable parameter
// rather than hardcoding it. Pair with SoftLimiter to bound the output.
//
// Usage:
//   sbl::dsp::AsymmetricShaper shaper;
//   shaper.set_asymmetry(0.1f);
//   float out = shaper.process(signal);
 
#ifndef SBL_DSP_PRIMITIVES_ASYMMETRIC_SHAPER_HPP_
#define SBL_DSP_PRIMITIVES_ASYMMETRIC_SHAPER_HPP_
 
#include <cstdint>
 
namespace sbl::dsp::primitives {
 
class AsymmetricShaper {
public:
    /// Set asymmetry depth (not a signal — structural character parameter)
    void set_asymmetry(float k) { k_ = k; }
 
    /// Current asymmetry depth
    float asymmetry() const { return k_; }
 
    /// Process a single sample
    float process(float x) {
        return x + k_ * x * x;
    }
 
    /// Process a block in-place
    void process(float* buf, uint16_t frames) {
        for (uint16_t i = 0; i < frames; ++i) {
            buf[i] = process(buf[i]);
        }
    }
 
private:
    float k_ = 0.0f;
};
 
} // namespace sbl::dsp::primitives
 
#endif // SBL_DSP_PRIMITIVES_ASYMMETRIC_SHAPER_HPP_