Line data    Source code

       1              : #pragma once
       2              : 
       3              : // Pitch shifting effect for semitone-based transposition.
       4              : // The shift ratio is r = 2^(semitones/12); the processor reads from a delay
       5              : // line/resampling window at rate r and crossfades windows to reduce clicks,
       6              : // producing y[n] from time-scaled input samples.
       7              : 
       8              : #include "audio/effects/effect.h"
       9              : #include <vector>
      10              : #include <array>
      11              : 
      12              : namespace Amplitron {
      13              : 
      14              : /**
      15              :  * Pitch Shifter — shifts pitch by +/- 12 semitones using a dual-tap
      16              :  * granular overlap-add algorithm.
      17              :  *
      18              :  * Two read pointers scan through a circular buffer at a rate determined by
      19              :  * the pitch ratio. A raised-cosine (Hann) crossfade between the two taps
      20              :  * hides the grain boundary discontinuities.
      21              :  *
      22              :  * Controls: Shift (semitones), Fine (cents), Mix.
      23              :  */
      24              : class PitchShifter : public Effect {
      25              : public:
      26              :     PitchShifter();
      27              :     void process(float* buffer, int num_samples) override;
      28              :     void set_sample_rate(int sample_rate) override;
      29              :     void reset() override;
      30            3 :     const char* name() const override { return "Pitch Shifter"; }
      31            6 :     const char* type_id() const override { return "Pitch Shifter"; }
      32          124 :     std::vector<EffectParam>& params() override { return params_; }
      33              : 
      34              : private:
      35              :     std::vector<EffectParam> params_;
      36              : 
      37              :     // Grain buffer
      38              :     std::vector<float> grain_buf_;
      39              :     int buf_size_ = 0;
      40              :     int write_pos_ = 0;
      41              : 
      42              :     // Two crossfading read taps (phase in [0, buf_size_))
      43              :     float read_phase_a_ = 0.0f;
      44              :     float read_phase_b_ = 0.0f;
      45              : 
      46              :     // Parameter smoothing
      47              :     float shift_smooth_ = 0.0f;
      48              :     float fine_smooth_ = 0.0f;
      49              :     float mix_smooth_ = 0.0f;
      50              : 
      51              :     // --- NEW OPTIMIZATION VARIABLES ---
      52              :     // Adds the function to pre-calculate the cosine math
      53              :     void build_hann_lut();
      54              : 
      55              :     // 8192 is a power of 2 (allows fast bitwise wrapping) and fits easily in L1 cache
      56              :     std::array<float, 8192> hann_lut_; 
      57              :     
      58              :     // Cached pitch ratio to avoid per-sample pow()
      59              :     float ratio_ = 1.0f;
      60              : 
      61              :     float read_linear(float phase) const;
      62              : };
      63              : 
      64              : } // namespace Amplitron