Line data    Source code

       1              : #include "audio/effects/dynamics/compressor.h"
       2              : 
       3              : #include "audio/effects/core/effect_factory.h"
       4              : 
       5              : namespace Amplitron {
       6              : 
       7            2 : static EffectRegistrar<Compressor> reg("Compressor");
       8              : 
       9           88 : Compressor::Compressor() {
      10          286 :     params_ = {
      11           66 :         {"Threshold", -20.0f, -60.0f, 0.0f, -20.0f, "dB",
      12           22 :          "Signal level at which compression begins. Signals above this level will be reduced in "
      13              :          "volume."},
      14           22 :         {"Ratio", 4.0f, 1.0f, 20.0f, 4.0f, ":1",
      15           22 :          "How strongly to reduce peaks that exceed the threshold. Higher values create a more "
      16              :          "squashed sound."},
      17           22 :         {"Attack", 5.0f, 0.1f, 50.0f, 5.0f, "ms",
      18           22 :          "How quickly the compressor reacts to peaks. Fast attack clamps down immediately, slow "
      19              :          "allows pick transients through."},
      20           22 :         {"Release", 100.0f, 10.0f, 500.0f, 100.0f, "ms",
      21           22 :          "How quickly the compressor stops reducing volume after the signal drops below "
      22              :          "threshold."},
      23           22 :         {"Makeup", 0.0f, 0.0f, 30.0f, 0.0f, "dB",
      24           22 :          "Gain boost applied after compression to compensate for the volume lost during peak "
      25              :          "reduction."},
      26          286 :     };
      27          132 : }
      28              : 
      29           36 : void Compressor::process(float* buffer, int num_samples) {
      30           36 :     if (!enabled_) return;
      31              : 
      32           36 :     float threshold_db = params_[0].value;
      33           36 :     float ratio = params_[1].value;
      34           36 :     float attack_ms = params_[2].value;
      35           36 :     float release_ms = params_[3].value;
      36           36 :     float makeup = db_to_linear(params_[4].value);
      37              : 
      38              :     // Parameter smoothing (anti-zipper) — keep short enough to reduce zipper noise
      39              :     // while limiting lag in fast attack/release settings.
      40           36 :     const float alpha = 1.0f - std::exp(-1.0f / (sample_rate_ * 0.002f));  // 2 ms
      41           36 :     smoothed_attack_ms_ += alpha * (attack_ms - smoothed_attack_ms_);
      42           36 :     smoothed_release_ms_ += alpha * (release_ms - smoothed_release_ms_);
      43              : 
      44           36 :     float attack_coeff = EnvelopeFollower::time_to_coeff(smoothed_attack_ms_, sample_rate_);
      45           36 :     float release_coeff = EnvelopeFollower::time_to_coeff(smoothed_release_ms_, sample_rate_);
      46              : 
      47        35364 :     for (int i = 0; i < num_samples; ++i) {
      48        35328 :         float envelope = env_.process_additive(buffer[i], attack_coeff, release_coeff);
      49              : 
      50        35328 :         float env_db = linear_to_db(envelope);
      51        35328 :         float gain_db = 0.0f;
      52        35328 :         if (env_db > threshold_db) {
      53        33759 :             gain_db = (threshold_db - env_db) * (1.0f - 1.0f / ratio);
      54        11253 :         }
      55              : 
      56        35328 :         float gain = db_to_linear(gain_db) * makeup;
      57        35328 :         buffer[i] *= gain;
      58        11776 :     }
      59           12 : }
      60              : 
      61           57 : void Compressor::reset() { env_.reset(); }
      62              : 
      63              : }  // namespace Amplitron