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Merge pull request godotengine#89088 from lander-vr/limiter
Add AudioEffectHardLimiter as a rework of audio limiter effect
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‎doc/classes/AudioEffectHardLimiter.xml‎

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<?xml version="1.0" encoding="UTF-8" ?>
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<class name="AudioEffectHardLimiter" inherits="AudioEffect" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
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<brief_description>
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Adds a hard limiter audio effect to an Audio bus.
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</brief_description>
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<description>
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A limiter is an effect designed to disallow sound from going over a given dB threshold. Hard limiters predict volume peaks, and will smoothly apply gain reduction when a peak crosses the ceiling threshold to prevent clipping and distortion. It preserves the waveform and prevents it from crossing the ceiling threshold. Adding one in the Master bus is recommended as a safety measure to prevent sudden volume peaks from occurring, and to prevent distortion caused by clipping.
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</description>
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<tutorials>
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<link title="Audio buses">$DOCS_URL/tutorials/audio/audio_buses.html</link>
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</tutorials>
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<members>
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<member name="ceiling_db" type="float" setter="set_ceiling_db" getter="get_ceiling_db" default="-0.3">
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The waveform's maximum allowed value, in decibels. This value can range from [code]-24.0[/code] to [code]0.0[/code].
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The default value of [code]-0.3[/code] prevents potential inter-sample peaks (ISP) from crossing over 0 dB, which can cause slight distortion on some older hardware.
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</member>
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<member name="pre_gain_db" type="float" setter="set_pre_gain_db" getter="get_pre_gain_db" default="0.0">
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Gain to apply before limiting, in decibels.
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</member>
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<member name="release" type="float" setter="set_release" getter="get_release" default="0.1">
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Time it takes in seconds for the gain reduction to fully release.
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</member>
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</members>
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</class>

‎doc/classes/AudioEffectLimiter.xml‎

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<?xml version="1.0" encoding="UTF-8" ?>
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<class name="AudioEffectLimiter" inherits="AudioEffect" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
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<class name="AudioEffectLimiter" inherits="AudioEffect" deprecated="Use [AudioEffectHardLimiter] instead." xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
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<brief_description>
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Adds a soft-clip limiter audio effect to an Audio bus.
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</brief_description>

‎servers/audio/effects/audio_effect_hard_limiter.cpp‎

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/**************************************************************************/
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/* audio_effect_hard_limiter.cpp */
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/**************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/**************************************************************************/
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/**************************************************************************/
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#include "audio_effect_hard_limiter.h"
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#include "servers/audio_server.h"
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void AudioEffectHardLimiterInstance::process(const AudioFrame *p_src_frames, AudioFrame *p_dst_frames, int p_frame_count) {
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float sample_rate = AudioServer::get_singleton()->get_mix_rate();
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float ceiling = Math::db_to_linear(base->ceiling);
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float release = base->release;
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float attack = base->attack;
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float pre_gain = Math::db_to_linear(base->pre_gain);
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for (int i = 0; i < p_frame_count; i++) {
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float sample_left = p_src_frames[i].left;
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float sample_right = p_src_frames[i].right;
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sample_left *= pre_gain;
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sample_right *= pre_gain;
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float largest_sample = MAX(ABS(sample_left), ABS(sample_right));
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release_factor = MAX(0.0, release_factor - 1.0 / sample_rate);
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release_factor = MIN(release_factor, release);
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if (release_factor > 0.0) {
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gain = Math::lerp(gain_target, 1.0f, 1.0f - release_factor / release);
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}
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if (largest_sample * gain > ceiling) {
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gain_target = ceiling / largest_sample;
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release_factor = release;
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attack_factor = attack;
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}
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// Lerp gain over attack time to avoid distortion.
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attack_factor = MAX(0.0f, attack_factor - 1.0f / sample_rate);
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if (attack_factor > 0.0) {
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gain = Math::lerp(gain_target, gain, 1.0f - attack_factor / attack);
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}
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int bucket_id = gain_bucket_cursor / gain_bucket_size;
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// If first item within the current bucket, reset the bucket.
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if (gain_bucket_cursor % gain_bucket_size == 0) {
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gain_buckets[bucket_id] = 1.0f;
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}
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gain_buckets[bucket_id] = MIN(gain_buckets[bucket_id], gain);
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gain_bucket_cursor = (gain_bucket_cursor + 1) % gain_samples_to_store;
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for (int j = 0; j < (int)gain_buckets.size(); j++) {
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gain = MIN(gain, gain_buckets[j]);
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}
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// Introduce latency by grabbing the AudioFrame stored previously,
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// then overwrite it with current audioframe, then update circular
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// buffer cursor.
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float dst_buffer_left = sample_buffer_left[sample_cursor];
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float dst_buffer_right = sample_buffer_right[sample_cursor];
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sample_buffer_left[sample_cursor] = sample_left;
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sample_buffer_right[sample_cursor] = sample_right;
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sample_cursor = (sample_cursor + 1) % sample_buffer_left.size();
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p_dst_frames[i].left = dst_buffer_left * gain;
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p_dst_frames[i].right = dst_buffer_right * gain;
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}
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}
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Ref<AudioEffectInstance> AudioEffectHardLimiter::instantiate() {
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Ref<AudioEffectHardLimiterInstance> ins;
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ins.instantiate();
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ins->base = Ref<AudioEffectHardLimiter>(this);
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float mix_rate = AudioServer::get_singleton()->get_mix_rate();
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for (int i = 0; i < (int)Math::ceil(mix_rate * attack) + 1; i++) {
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ins->sample_buffer_left.push_back(0.0f);
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ins->sample_buffer_right.push_back(0.0f);
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}
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ins->gain_samples_to_store = (int)Math::ceil(mix_rate * (attack + sustain) + 1);
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ins->gain_bucket_size = (int)(mix_rate * attack);
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for (int i = 0; i < ins->gain_samples_to_store; i += ins->gain_bucket_size) {
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ins->gain_buckets.push_back(1.0f);
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}
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return ins;
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}
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void AudioEffectHardLimiter::set_ceiling_db(float p_ceiling) {
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ceiling = p_ceiling;
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}
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float AudioEffectHardLimiter::get_ceiling_db() const {
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return ceiling;
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}
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float AudioEffectHardLimiter::get_pre_gain_db() const {
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return pre_gain;
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}
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void AudioEffectHardLimiter::set_pre_gain_db(const float p_pre_gain) {
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pre_gain = p_pre_gain;
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}
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float AudioEffectHardLimiter::get_release() const {
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return release;
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}
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void AudioEffectHardLimiter::set_release(const float p_release) {
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release = p_release;
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}
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void AudioEffectHardLimiter::_bind_methods() {
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ClassDB::bind_method(D_METHOD("set_ceiling_db", "ceiling"), &AudioEffectHardLimiter::set_ceiling_db);
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ClassDB::bind_method(D_METHOD("get_ceiling_db"), &AudioEffectHardLimiter::get_ceiling_db);
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ClassDB::bind_method(D_METHOD("set_pre_gain_db", "p_pre_gain"), &AudioEffectHardLimiter::set_pre_gain_db);
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ClassDB::bind_method(D_METHOD("get_pre_gain_db"), &AudioEffectHardLimiter::get_pre_gain_db);
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ClassDB::bind_method(D_METHOD("set_release", "p_release"), &AudioEffectHardLimiter::set_release);
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ClassDB::bind_method(D_METHOD("get_release"), &AudioEffectHardLimiter::get_release);
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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");
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ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "ceiling_db", PROPERTY_HINT_RANGE, "-24,0.0,0.01,suffix:dB"), "set_ceiling_db", "get_ceiling_db");
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ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "release", PROPERTY_HINT_RANGE, "0.01,3,0.01"), "set_release", "get_release");
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}

‎servers/audio/effects/audio_effect_hard_limiter.h‎

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/**************************************************************************/
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/* audio_effect_hard_limiter.h */
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/**************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/**************************************************************************/
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/**************************************************************************/
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#ifndef AUDIO_EFFECT_HARD_LIMITER_H
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#define AUDIO_EFFECT_HARD_LIMITER_H
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#include "servers/audio/audio_effect.h"
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class AudioEffectHardLimiter;
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class AudioEffectHardLimiterInstance : public AudioEffectInstance {
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GDCLASS(AudioEffectHardLimiterInstance, AudioEffectInstance);
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friend class AudioEffectHardLimiter;
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Ref<AudioEffectHardLimiter> base;
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private:
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int sample_cursor = 0;
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float release_factor = 0;
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float attack_factor = 0;
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float gain = 1;
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float gain_target = 1;
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LocalVector<float> sample_buffer_left;
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LocalVector<float> sample_buffer_right;
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int gain_samples_to_store = 0;
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int gain_bucket_cursor = 0;
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int gain_bucket_size = 0;
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LocalVector<float> gain_buckets;
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public:
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virtual void process(const AudioFrame *p_src_frames, AudioFrame *p_dst_frames, int p_frame_count) override;
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};
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class AudioEffectHardLimiter : public AudioEffect {
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GDCLASS(AudioEffectHardLimiter, AudioEffect);
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friend class AudioEffectHardLimiterInstance;
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float pre_gain = 0.0f;
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float ceiling = -0.3f;
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float sustain = 0.02f;
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float release = 0.1f;
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const float attack = 0.002;
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protected:
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static void _bind_methods();
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public:
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void set_ceiling_db(float p_ceiling);
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float get_ceiling_db() const;
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void set_release(float p_release);
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float get_release() const;
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void set_pre_gain_db(float p_pre_gain);
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float get_pre_gain_db() const;
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Ref<AudioEffectInstance> instantiate() override;
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};
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#endif // AUDIO_EFFECT_HARD_LIMITER_H

‎servers/register_server_types.cpp‎

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#include "audio/effects/audio_effect_distortion.h"
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#include "audio/effects/audio_effect_eq.h"
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#include "audio/effects/audio_effect_filter.h"
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#include "audio/effects/audio_effect_hard_limiter.h"
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#include "audio/effects/audio_effect_limiter.h"
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#include "audio/effects/audio_effect_panner.h"
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#include "audio/effects/audio_effect_phaser.h"
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GDREGISTER_CLASS(AudioEffectDelay);
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GDREGISTER_CLASS(AudioEffectCompressor);
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GDREGISTER_CLASS(AudioEffectLimiter);
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GDREGISTER_CLASS(AudioEffectHardLimiter);
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GDREGISTER_CLASS(AudioEffectPitchShift);
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GDREGISTER_CLASS(AudioEffectPhaser);
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