Line data    Source code

       1              : #include "audio/effects/distortion/distortion.h"
       2              : 
       3              : #include "audio/effects/core/effect_factory.h"
       4              : 
       5              : namespace Amplitron {
       6              : 
       7            2 : static EffectRegistrar<Distortion> reg("Distortion");
       8              : 
       9          120 : Distortion::Distortion() {
      10          270 :     params_ = {
      11           90 :         {"Drive", 2.0f, 1.0f, 20.0f, 2.0f, "x",
      12           30 :          "Amount of input gain slamming into the hard clippers. Creates aggressive, dense harmonic "
      13              :          "distortion."},
      14           30 :         {"Tone", 0.6f, 0.0f, 1.0f, 0.6f, "",
      15           30 :          "Low-pass filter cutoff to tame the fizzy high-end generated by hard clipping."},
      16           30 :         {"Level", 0.5f, 0.0f, 1.0f, 0.5f, "",
      17           30 :          "Master output volume of the pedal. Useful to match volume with the pedal bypassed."},
      18          270 :     };
      19          120 :     drive_smoothed_ = params_[0].value;
      20           90 :     tone_smoothed_ = params_[1].value;
      21           90 :     level_smoothed_ = params_[2].value;
      22          210 : }
      23              : 
      24           60 : void Distortion::process(float* buffer, int num_samples) {
      25           60 :     if (!enabled_) return;
      26              : 
      27           24 :     const float mix = mix_.load(std::memory_order_relaxed);
      28              : 
      29              :     // One-pole smoothing: advance states toward raw param targets each block
      30           24 :     const float alpha = 1.0f - std::exp(-1.0f / (sample_rate_ * 0.010f));  // 10 ms
      31           24 :     drive_smoothed_ += alpha * (params_[0].value - drive_smoothed_);
      32           24 :     tone_smoothed_ += alpha * (params_[1].value - tone_smoothed_);
      33           24 :     level_smoothed_ += alpha * (params_[2].value - level_smoothed_);
      34              : 
      35           24 :     float drive = drive_smoothed_;
      36           24 :     float tone = tone_smoothed_;
      37           24 :     float level = level_smoothed_;
      38              : 
      39              :     // Tone control: simple one-pole LP filter coefficient
      40           24 :     float lp_coeff = 0.1f + tone * 0.8f;
      41              : 
      42         6168 :     for (int i = 0; i < num_samples; ++i) {
      43         6144 :         float dry = buffer[i];
      44              : 
      45              :         // Apply drive gain
      46         6144 :         float x = buffer[i] * drive;
      47              : 
      48              :         // Soft path (tube-like via tanh + soft clip)
      49         6144 :         float x_soft = soft_clip(fast_tanh(x) * 1.5f);
      50              : 
      51              :         // Hard path (hard clip at unity)
      52         6144 :         float x_hard = hard_clip(x, 1.0f);
      53              : 
      54              :         // Blend: more drive → more hard clipping
      55         4096 :         float hard_amount =
      56         6144 :             (drive - params_[0].min_val) / (params_[0].max_val - params_[0].min_val);
      57         6144 :         x = x_soft * (1.0f - hard_amount) + x_hard * hard_amount;
      58              : 
      59              :         // Tone filter (one-pole LP)
      60         6144 :         x = tone_lp_.lp(x, lp_coeff);
      61              : 
      62              :         // Output level
      63         6144 :         x *= level;
      64              : 
      65              :         // Wet/dry mix
      66         6144 :         buffer[i] = dry * (1.0f - mix) + x * mix;
      67         2048 :     }
      68           20 : }
      69              : 
      70           90 : void Distortion::reset() { tone_lp_.reset(); }
      71              : 
      72              : }  // namespace Amplitron