text: /*************************************************************************/
  /*  audio_effect_limiter.cpp                                             */
  /*************************************************************************/
  /*                       This file is part of:                           */
  /*                           GODOT ENGINE                                */
  /*                      https://godotengine.org                          */
  /*************************************************************************/
  /* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
  /* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
  /*                                                                       */
  /* Permission is hereby granted, free of charge, to any person obtaining */
  /* a copy of this software and associated documentation files (the       */
  /* "Software"), to deal in the Software without restriction, including   */
  /* without limitation the rights to use, copy, modify, merge, publish,   */
  /* distribute, sublicense, and/or sell copies of the Software, and to    */
  /* permit persons to whom the Software is furnished to do so, subject to */
  /* the following conditions:                                             */
  /*                                                                       */
  /* The above copyright notice and this permission notice shall be        */
  /* included in all copies or substantial portions of the Software.       */
  /*                                                                       */
  /* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
  /* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
  /* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
  /* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
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  /*************************************************************************/
  
  #include "audio_effect_limiter.h"
  
  void AudioEffectLimiterInstance::process(const AudioFrame *p_src_frames, AudioFrame *p_dst_frames, int p_frame_count) {
  
  	float threshdb = base->threshold;
  	float ceiling = Math::db2linear(base->ceiling);
  	float ceildb = base->ceiling;
  	float makeup = Math::db2linear(ceildb - threshdb);
  	float sc = -base->soft_clip;
  	float scv = Math::db2linear(sc);
  	float peakdb = ceildb + 25;
  	float scmult = Math::abs((ceildb - sc) / (peakdb - sc));
  
  	for (int i = 0; i < p_frame_count; i++) {
  
  		float spl0 = p_src_frames[i].l;
  		float spl1 = p_src_frames[i].r;
  		spl0 = spl0 * makeup;
  		spl1 = spl1 * makeup;
  		float sign0 = (spl0 < 0.0 ? -1.0 : 1.0);
  		float sign1 = (spl1 < 0.0 ? -1.0 : 1.0);
  		float abs0 = Math::abs(spl0);
  		float abs1 = Math::abs(spl1);
  		float overdb0 = Math::linear2db(abs0) - ceildb;
  		float overdb1 = Math::linear2db(abs1) - ceildb;
  
  		if (abs0 > scv) {
  			spl0 = sign0 * (scv + Math::db2linear(overdb0 * scmult));
  		}
  		if (abs1 > scv) {
  			spl1 = sign1 * (scv + Math::db2linear(overdb1 * scmult));
  		}
  
  		spl0 = MIN(ceiling, Math::abs(spl0)) * (spl0 < 0.0 ? -1.0 : 1.0);
  		spl1 = MIN(ceiling, Math::abs(spl1)) * (spl1 < 0.0 ? -1.0 : 1.0);
  
  		p_dst_frames[i].l = spl0;
  		p_dst_frames[i].r = spl1;
  	}
  }
  
  Ref<AudioEffectInstance> AudioEffectLimiter::instance() {
  	Ref<AudioEffectLimiterInstance> ins;
  	ins.instance();
  	ins->base = Ref<AudioEffectLimiter>(this);
  
  	return ins;
  }
  
  void AudioEffectLimiter::set_threshold_db(float p_threshold) {
  
  	threshold = p_threshold;
  }
  
  float AudioEffectLimiter::get_threshold_db() const {
  
  	return threshold;
  }
  
  void AudioEffectLimiter::set_ceiling_db(float p_ceiling) {
  
  	ceiling = p_ceiling;
  }
  float AudioEffectLimiter::get_ceiling_db() const {
  
  	return ceiling;
  }
  
  void AudioEffectLimiter::set_soft_clip_db(float p_soft_clip) {
  
  	soft_clip = p_soft_clip;
  }
  float AudioEffectLimiter::get_soft_clip_db() const {
  
  	return soft_clip;
  }
  
  void AudioEffectLimiter::set_soft_clip_ratio(float p_soft_clip) {
  
  	soft_clip_ratio = p_soft_clip;
  }
  float AudioEffectLimiter::get_soft_clip_ratio() const {
  
  	return soft_clip_ratio;
  }
  
  void AudioEffectLimiter::_bind_methods() {
  
  	ClassDB::bind_method(D_METHOD("set_ceiling_db", "ceiling"), &AudioEffectLimiter::set_ceiling_db);
  	ClassDB::bind_method(D_METHOD("get_ceiling_db"), &AudioEffectLimiter::get_ceiling_db);
  
  	ClassDB::bind_method(D_METHOD("set_threshold_db", "threshold"), &AudioEffectLimiter::set_threshold_db);
  	ClassDB::bind_method(D_METHOD("get_threshold_db"), &AudioEffectLimiter::get_threshold_db);
  
  	ClassDB::bind_method(D_METHOD("set_soft_clip_db", "soft_clip"), &AudioEffectLimiter::set_soft_clip_db);
  	ClassDB::bind_method(D_METHOD("get_soft_clip_db"), &AudioEffectLimiter::get_soft_clip_db);
  
  	ClassDB::bind_method(D_METHOD("set_soft_clip_ratio", "soft_clip"), &AudioEffectLimiter::set_soft_clip_ratio);
  	ClassDB::bind_method(D_METHOD("get_soft_clip_ratio"), &AudioEffectLimiter::get_soft_clip_ratio);
  
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "ceiling_db", PROPERTY_HINT_RANGE, "-20,-0.1,0.1"), "set_ceiling_db", "get_ceiling_db");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "threshold_db", PROPERTY_HINT_RANGE, "-30,0,0.1"), "set_threshold_db", "get_threshold_db");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "soft_clip_db", PROPERTY_HINT_RANGE, "0,6,0.1"), "set_soft_clip_db", "get_soft_clip_db");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "soft_clip_ratio", PROPERTY_HINT_RANGE, "3,20,0.1"), "set_soft_clip_ratio", "get_soft_clip_ratio");
  }
  
  AudioEffectLimiter::AudioEffectLimiter() {
  	threshold = 0;
  	ceiling = -0.1;
  	soft_clip = 2;
  	soft_clip_ratio = 10;
  }
  