Line data    Source code

       1              : #include "audio/effects/distortion.h"
       2              : #include "audio/effects/effect_factory.h"
       3              : 
       4              : namespace Amplitron {
       5              : 
       6            2 : static EffectRegistrar<Distortion> reg("Distortion");
       7              : 
       8          100 : Distortion::Distortion() {
       9          225 :     params_ = {
      10           75 :         {"Drive",  2.0f,  1.0f, 20.0f,  2.0f, "x", "Amount of input gain slamming into the hard clippers. Creates aggressive, dense harmonic distortion."},
      11           25 :         {"Tone",   0.6f,  0.0f,  1.0f,  0.6f, "", "Low-pass filter cutoff to tame the fizzy high-end generated by hard clipping."},
      12           25 :         {"Level",  0.5f,  0.0f,  1.0f,  0.5f, "", "Master output volume of the pedal. Useful to match volume with the pedal bypassed."},
      13          225 :     };
      14          100 :     drive_smoothed_ = params_[0].value;
      15           75 :     tone_smoothed_  = params_[1].value;
      16           75 :     level_smoothed_ = params_[2].value;
      17          175 : }
      18              : 
      19           27 : void Distortion::process(float* buffer, int num_samples) {
      20           27 :     if (!enabled_) return;
      21              : 
      22              :     // One-pole smoothing: advance states toward raw param targets each block
      23           24 :     const float alpha = 1.0f - std::exp(-1.0f / (sample_rate_ * 0.010f)); // 10 ms
      24           24 :     drive_smoothed_ += alpha * (params_[0].value - drive_smoothed_);
      25           24 :     tone_smoothed_  += alpha * (params_[1].value - tone_smoothed_);
      26           24 :     level_smoothed_ += alpha * (params_[2].value - level_smoothed_);
      27              : 
      28           24 :     float drive = drive_smoothed_;
      29           24 :     float tone = tone_smoothed_;
      30           24 :     float level = level_smoothed_;
      31              : 
      32              :     // Tone control: simple one-pole LP filter coefficient
      33           24 :     float lp_coeff = 0.1f + tone * 0.8f;
      34              : 
      35         6168 :     for (int i = 0; i < num_samples; ++i) {
      36         6144 :         float dry = buffer[i];
      37              : 
      38              :         // Apply drive gain
      39         6144 :         float x = buffer[i] * drive;
      40              : 
      41              :         // Soft path (tube-like via tanh + soft clip)
      42         6144 :         float x_soft = soft_clip(fast_tanh(x) * 1.5f);
      43              : 
      44              :         // Hard path (hard clip at unity)
      45         6144 :         float x_hard = hard_clip(x, 1.0f);
      46              : 
      47              :         // Blend: more drive → more hard clipping
      48         6144 :         float hard_amount = (drive - 1.0f) / 19.0f; // 0 at drive=1, 1 at drive=20
      49         6144 :         x = x_soft * (1.0f - hard_amount) + x_hard * hard_amount;
      50              : 
      51              :         // Tone filter (one-pole LP)
      52         6144 :         x = tone_lp_.lp(x, lp_coeff);
      53              : 
      54              :         // Output level
      55         6144 :         x *= level;
      56              : 
      57              :         // Wet/dry mix
      58         6144 :         buffer[i] = dry * (1.0f - mix_) + x * mix_;
      59         2048 :     }
      60            9 : }
      61              : 
      62           69 : void Distortion::reset() {
      63           69 :     tone_lp_.reset();
      64           69 : }
      65              : 
      66              : } // namespace Amplitron