147 lines
3.8 KiB
C++
147 lines
3.8 KiB
C++
#pragma once
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#include <cmath>
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#include "audio_math.h"
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namespace trnr {
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template <typename sample>
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class pump {
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public:
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pump()
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: attack_ms(10.f)
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, release_ms(100.f)
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, hp_filter(80.0f)
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, threshold_db(0.f)
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, ratio(1000.0f)
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, filter_frq(40000.f)
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, filter_exp(0.f)
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, treble_boost(0.f)
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{
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set_samplerate(44100);
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}
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void set_samplerate(double _samplerate)
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{
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samplerate = _samplerate;
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set_attack(attack_ms);
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set_release(release_ms);
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}
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void set_ratio(float value) { ratio = value; }
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/* set threshold in db */
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void set_threshold(float value) { threshold_db = value; }
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/* set attack in ms */
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void set_attack(float value)
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{
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attack_ms = value;
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attack_coef = exp(-1000.0 / (attack_ms * samplerate));
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}
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/* set release in ms */
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void set_release(float value)
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{
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release_ms = value;
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release_coef = exp(-1000.0 / (release_ms * samplerate));
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}
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/* lowpass filter frequency in hz */
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void set_filter_frq(float value) { filter_frq = value; }
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/* accentuates the filter pumping effect */
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void set_filter_exp(float value) { filter_exp = value; }
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void process_block(sample** audio, sample** sidechain, int frames)
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{
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// highpass filter coefficients
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float hp_x = std::exp(-2.0 * M_PI * hp_filter / samplerate);
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float hp_a0 = 1.0 - hp_x;
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float hp_b1 = -hp_x;
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// top end boost filter coefficients
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float bst_x = exp(-2.0 * M_PI * 5000.0 / samplerate);
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float bst_a0 = 1.0 - bst_x;
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float bst_b1 = -bst_x;
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for (int i = 0; i < frames; i++) {
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sample input_l = audio[0][i];
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sample input_r = audio[1][i];
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sample sidechain_in = (sidechain[0][i] + sidechain[1][i]) / 2.0;
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// highpass filter sidechain signal
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filtered = hp_a0 * sidechain_in - hp_b1 * filtered;
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sidechain_in = sidechain_in - filtered;
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// rectify sidechain input for envelope following
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float link = std::fabs(sidechain_in);
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float linked_db = trnr::lin_2_db(link);
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// cut envelope below threshold
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float overshoot_db = linked_db - (threshold_db - 10.0);
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if (overshoot_db < 0.0) overshoot_db = 0.0;
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// process envelope
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if (overshoot_db > envelope_db) {
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envelope_db = overshoot_db + attack_coef * (envelope_db - overshoot_db);
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} else {
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envelope_db = overshoot_db + release_coef * (envelope_db - overshoot_db);
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}
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float slope = 1.f / ratio;
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// transfer function
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float gain_reduction_db = envelope_db * (slope - 1.0);
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float gain_reduction_lin = db_2_lin(gain_reduction_db);
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// compress left and right signals
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sample output_l = input_l * gain_reduction_lin;
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sample output_r = input_r * gain_reduction_lin;
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if (filter_exp > 0.f) {
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// one pole lowpass filter with envelope applied to frequency for pumping effect
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float freq = filter_frq * pow(gain_reduction_lin, filter_exp);
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float lp_x = exp(-2.0 * M_PI * freq / samplerate);
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float lp_a0 = 1.0 - lp_x;
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float lp_b1 = -lp_x;
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filtered_l = lp_a0 * output_l - lp_b1 * filtered_l;
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filtered_r = lp_a0 * output_r - lp_b1 * filtered_r;
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}
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// top end boost
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boosted_l = bst_a0 * filtered_l - bst_b1 * boosted_l;
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boosted_r = bst_a0 * filtered_r - bst_b1 * boosted_r;
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output_l = filtered_l + (filtered_l - boosted_l) * treble_boost;
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output_r = filtered_r + (filtered_r - boosted_r) * treble_boost;
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// calculate makeup gain
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float makeup_lin = trnr::db_2_lin(-threshold_db / 5.f);
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audio[0][i] = input_l * gain_reduction_lin * makeup_lin;
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audio[1][i] = input_r * gain_reduction_lin * makeup_lin;
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}
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}
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private:
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double samplerate;
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float threshold_db = 0.f;
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float attack_ms;
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float release_ms;
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float hp_filter;
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float ratio;
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float filter_frq;
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float filter_exp;
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float treble_boost;
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sample filtered;
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sample filtered_l = 0;
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sample filtered_r = 0;
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sample boosted_l = 0;
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sample boosted_r = 0;
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float attack_coef;
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float release_coef;
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float envelope_db = 0;
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};
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} // namespace trnr
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