godot/servers/audio/effects/audio_effect_limiter.cpp

/**************************************************************************/
/*  audio_effect_limiter.cpp                                              */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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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::db_to_linear(base->ceiling);
	float ceildb = base->ceiling;
	float makeup = Math::db_to_linear(ceildb - threshdb);
	float sc = -base->soft_clip;
	float scv = Math::db_to_linear(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::linear_to_db(abs0) - ceildb;
		float overdb1 = Math::linear_to_db(abs1) - ceildb;

		if (abs0 > scv) {
			spl0 = sign0 * (scv + Math::db_to_linear(overdb0 * scmult));
		}
		if (abs1 > scv) {
			spl1 = sign1 * (scv + Math::db_to_linear(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::instantiate() {
	Ref<AudioEffectLimiterInstance> ins;
	ins.instantiate();
	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::FLOAT, "ceiling_db", PROPERTY_HINT_RANGE, "-20,-0.1,0.1,suffix:dB"), "set_ceiling_db", "get_ceiling_db");
	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "threshold_db", PROPERTY_HINT_RANGE, "-30,0,0.1,suffix:dB"), "set_threshold_db", "get_threshold_db");
	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "soft_clip_db", PROPERTY_HINT_RANGE, "0,6,0.1,suffix:dB"), "set_soft_clip_db", "get_soft_clip_db");
	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "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;
}