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/**************************************************************************/
/* audio_effect_hard_limiter.cpp */
/**************************************************************************/
/* This file is part of: */
/* REDOT ENGINE */
/* https://redotengine.org */
/**************************************************************************/
/* Copyright (c) 2024-present Redot Engine contributors */
/* (see REDOT_AUTHORS.md) */
/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
/* */
/* 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 */
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
/**************************************************************************/
#include "audio_effect_hard_limiter.h"
#include "servers/audio_server.h"
void AudioEffectHardLimiterInstance::process(const AudioFrame *p_src_frames, AudioFrame *p_dst_frames, int p_frame_count) {
float sample_rate = AudioServer::get_singleton()->get_mix_rate();
float ceiling = Math::db_to_linear(base->ceiling);
float release = base->release;
float attack = base->attack;
float pre_gain = Math::db_to_linear(base->pre_gain);
for (int i = 0; i < p_frame_count; i++) {
float sample_left = p_src_frames[i].left;
float sample_right = p_src_frames[i].right;
sample_left *= pre_gain;
sample_right *= pre_gain;
float largest_sample = MAX(ABS(sample_left), ABS(sample_right));
release_factor = MAX(0.0, release_factor - 1.0 / sample_rate);
release_factor = MIN(release_factor, release);
if (release_factor > 0.0) {
gain = Math::lerp(gain_target, 1.0f, 1.0f - release_factor / release);
}
if (largest_sample * gain > ceiling) {
gain_target = ceiling / largest_sample;
release_factor = release;
attack_factor = attack;
}
// Lerp gain over attack time to avoid distortion.
attack_factor = MAX(0.0f, attack_factor - 1.0f / sample_rate);
if (attack_factor > 0.0) {
gain = Math::lerp(gain_target, gain, 1.0f - attack_factor / attack);
}
int bucket_id = gain_bucket_cursor / gain_bucket_size;
// If first item within the current bucket, reset the bucket.
if (gain_bucket_cursor % gain_bucket_size == 0) {
gain_buckets[bucket_id] = 1.0f;
}
gain_buckets[bucket_id] = MIN(gain_buckets[bucket_id], gain);
gain_bucket_cursor = (gain_bucket_cursor + 1) % gain_samples_to_store;
for (int j = 0; j < (int)gain_buckets.size(); j++) {
gain = MIN(gain, gain_buckets[j]);
}
// Introduce latency by grabbing the AudioFrame stored previously,
// then overwrite it with current audioframe, then update circular
// buffer cursor.
float dst_buffer_left = sample_buffer_left[sample_cursor];
float dst_buffer_right = sample_buffer_right[sample_cursor];
sample_buffer_left[sample_cursor] = sample_left;
sample_buffer_right[sample_cursor] = sample_right;
sample_cursor = (sample_cursor + 1) % sample_buffer_left.size();
p_dst_frames[i].left = dst_buffer_left * gain;
p_dst_frames[i].right = dst_buffer_right * gain;
}
}
Ref<AudioEffectInstance> AudioEffectHardLimiter::instantiate() {
Ref<AudioEffectHardLimiterInstance> ins;
ins.instantiate();
ins->base = Ref<AudioEffectHardLimiter>(this);
float mix_rate = AudioServer::get_singleton()->get_mix_rate();
for (int i = 0; i < (int)Math::ceil(mix_rate * attack) + 1; i++) {
ins->sample_buffer_left.push_back(0.0f);
ins->sample_buffer_right.push_back(0.0f);
}
ins->gain_samples_to_store = (int)Math::ceil(mix_rate * (attack + sustain) + 1);
ins->gain_bucket_size = (int)(mix_rate * attack);
for (int i = 0; i < ins->gain_samples_to_store; i += ins->gain_bucket_size) {
ins->gain_buckets.push_back(1.0f);
}
return ins;
}
void AudioEffectHardLimiter::set_ceiling_db(float p_ceiling) {
ceiling = p_ceiling;
}
float AudioEffectHardLimiter::get_ceiling_db() const {
return ceiling;
}
float AudioEffectHardLimiter::get_pre_gain_db() const {
return pre_gain;
}
void AudioEffectHardLimiter::set_pre_gain_db(const float p_pre_gain) {
pre_gain = p_pre_gain;
}
float AudioEffectHardLimiter::get_release() const {
return release;
}
void AudioEffectHardLimiter::set_release(const float p_release) {
release = p_release;
}
void AudioEffectHardLimiter::_bind_methods() {
ClassDB::bind_method(D_METHOD("set_ceiling_db", "ceiling"), &AudioEffectHardLimiter::set_ceiling_db);
ClassDB::bind_method(D_METHOD("get_ceiling_db"), &AudioEffectHardLimiter::get_ceiling_db);
ClassDB::bind_method(D_METHOD("set_pre_gain_db", "p_pre_gain"), &AudioEffectHardLimiter::set_pre_gain_db);
ClassDB::bind_method(D_METHOD("get_pre_gain_db"), &AudioEffectHardLimiter::get_pre_gain_db);
ClassDB::bind_method(D_METHOD("set_release", "p_release"), &AudioEffectHardLimiter::set_release);
ClassDB::bind_method(D_METHOD("get_release"), &AudioEffectHardLimiter::get_release);
ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "pre_gain_db", PROPERTY_HINT_RANGE, "-24,24,0.01,suffix:dB"), "set_pre_gain_db", "get_pre_gain_db");
ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "ceiling_db", PROPERTY_HINT_RANGE, "-24,0.0,0.01,suffix:dB"), "set_ceiling_db", "get_ceiling_db");
ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "release", PROPERTY_HINT_RANGE, "0.01,3,0.01"), "set_release", "get_release");
}
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