convert pump compressor to procedural approach

dynamics/pump.h

@@ -1,66 +1,92 @@
 #pragma once
 
-#include <cmath>
 #include "audio_math.h"
+#include <cmath>
 
 namespace trnr {
+struct pump {
+	double samplerate;
+	float threshold_db = 0.f;
+	float attack_ms = 10.f;
+	float release_ms = 100.f;
+	float hp_filter = 80.f;
+	float ratio = 1000.f;
+	float filter_frq = 40000.f;
+	float filter_exp = 0.f;
+	float treble_boost = 0.f;
+
+	float filtered = 0.f;
+	float filtered_l = 0.f;
+	float filtered_r = 0.f;
+	float boosted_l = 0.f;
+	float boosted_r = 0.f;
+	float attack_coef = 0.f;
+	float release_coef = 0.f;
+	float envelope_db = 0.f;
+};
+
+enum pump_param {
+	PUMP_THRESHOLD,
+	PUMP_ATTACK,
+	PUMP_RELEASE,
+	PUMP_HP_FILTER,
+	PUMP_RATIO,
+	PUMP_FILTER_FRQ,
+	PUMP_FILTER_EXP,
+	PUMP_TREBLE_BOOST
+};
+
+inline void pump_set_param(pump& p, pump_param param, float value)
+{
+	switch (param) {
+	case PUMP_THRESHOLD:
+		p.threshold_db = value;
+		break;
+	case PUMP_ATTACK:
+		p.attack_ms = value;
+		p.attack_coef = exp(-1000.0 / (p.attack_ms * p.samplerate));
+		break;
+	case PUMP_RELEASE:
+		p.release_ms = value;
+		p.release_coef = exp(-1000.0 / (p.release_ms * p.samplerate));
+		break;
+	case PUMP_HP_FILTER:
+		p.hp_filter = value;
+		break;
+	case PUMP_RATIO:
+		p.ratio = value;
+		break;
+	case PUMP_FILTER_FRQ:
+		p.filter_frq = value;
+		break;
+	case PUMP_FILTER_EXP:
+		p.filter_exp = value;
+		break;
+	case PUMP_TREBLE_BOOST:
+		p.treble_boost = value;
+		break;
+	default:
+		break;
+	}
+}
+
+inline void pump_init(pump& p, double samplerate)
+{
+	p.samplerate = samplerate;
+	pump_set_param(p, PUMP_ATTACK, p.attack_ms);
+	pump_set_param(p, PUMP_RELEASE, p.release_ms);
+}
+
 template <typename sample>
-class pump {
+inline void pump_process_block(pump& p, sample** audio, sample** sidechain, int frames)
-public:
-	pump()
-		: attack_ms(10.f)
-		, release_ms(100.f)
-		, hp_filter(80.0f)
-		, threshold_db(0.f)
-		, ratio(1000.0f)
-		, filter_frq(40000.f)
-		, filter_exp(0.f)
-		, treble_boost(0.f)
-	{
-		set_samplerate(44100);
-	}
-
-	void set_samplerate(double _samplerate)
-	{
-		samplerate = _samplerate;
-		set_attack(attack_ms);
-		set_release(release_ms);
-	}
-
-	void set_ratio(float value) { ratio = value; }
-
-	/* set threshold in db */
-	void set_threshold(float value) { threshold_db = value; }
-
-	/* set attack in ms */
-	void set_attack(float value)
-	{
-		attack_ms = value;
-		attack_coef = exp(-1000.0 / (attack_ms * samplerate));
-	}
-
-	/* set release in ms */
-	void set_release(float value)
-	{
-		release_ms = value;
-		release_coef = exp(-1000.0 / (release_ms * samplerate));
-	}
-
-	/* lowpass filter frequency in hz */
-	void set_filter_frq(float value) { filter_frq = value; }
-
-	/* accentuates the filter pumping effect */
-	void set_filter_exp(float value) { filter_exp = value; }
-
-	void process_block(sample** audio, sample** sidechain, int frames)
 {
 	// highpass filter coefficients
-		float hp_x = std::exp(-2.0 * M_PI * hp_filter / samplerate);
+	float hp_x = std::exp(-2.0 * M_PI * p.hp_filter / p.samplerate);
 	float hp_a0 = 1.0 - hp_x;
 	float hp_b1 = -hp_x;
 
 	// top end boost filter coefficients
-		float bst_x = exp(-2.0 * M_PI * 5000.0 / samplerate);
+	float bst_x = exp(-2.0 * M_PI * 5000.0 / p.samplerate);
 	float bst_a0 = 1.0 - bst_x;
 	float bst_b1 = -bst_x;
 
@@ -72,76 +98,55 @@ public:
 		sample sidechain_in = (sidechain[0][i] + sidechain[1][i]) / 2.0;
 
 		// highpass filter sidechain signal
-			filtered = hp_a0 * sidechain_in - hp_b1 * filtered;
+		p.filtered = hp_a0 * sidechain_in - hp_b1 * p.filtered;
-			sidechain_in = sidechain_in - filtered;
+		sidechain_in = sidechain_in - p.filtered;
 
 		// rectify sidechain input for envelope following
 		float link = std::fabs(sidechain_in);
 		float linked_db = trnr::lin_2_db(link);
 
 		// cut envelope below threshold
-			float overshoot_db = linked_db - (threshold_db - 10.0);
+		float overshoot_db = linked_db - (p.threshold_db - 10.0);
 		if (overshoot_db < 0.0) overshoot_db = 0.0;
 
 		// process envelope
-			if (overshoot_db > envelope_db) {
+		if (overshoot_db > p.envelope_db) {
-				envelope_db = overshoot_db + attack_coef * (envelope_db - overshoot_db);
+			p.envelope_db = overshoot_db + p.attack_coef * (p.envelope_db - overshoot_db);
 		} else {
-				envelope_db = overshoot_db + release_coef * (envelope_db - overshoot_db);
+			p.envelope_db = overshoot_db + p.release_coef * (p.envelope_db - overshoot_db);
 		}
 
-			float slope = 1.f / ratio;
+		float slope = 1.f / p.ratio;
 
 		// transfer function
-			float gain_reduction_db = envelope_db * (slope - 1.0);
+		float gain_reduction_db = p.envelope_db * (slope - 1.0);
 		float gain_reduction_lin = db_2_lin(gain_reduction_db);
 
 		// compress left and right signals
 		sample output_l = input_l * gain_reduction_lin;
 		sample output_r = input_r * gain_reduction_lin;
 
-			if (filter_exp > 0.f) {
+		if (p.filter_exp > 0.f) {
 			// one pole lowpass filter with envelope applied to frequency for pumping effect
-				float freq = filter_frq * pow(gain_reduction_lin, filter_exp);
+			float freq = p.filter_frq * pow(gain_reduction_lin, p.filter_exp);
-				float lp_x = exp(-2.0 * M_PI * freq / samplerate);
+			float lp_x = exp(-2.0 * M_PI * freq / p.samplerate);
 			float lp_a0 = 1.0 - lp_x;
 			float lp_b1 = -lp_x;
-				filtered_l = lp_a0 * output_l - lp_b1 * filtered_l;
+			p.filtered_l = lp_a0 * output_l - lp_b1 * p.filtered_l;
-				filtered_r = lp_a0 * output_r - lp_b1 * filtered_r;
+			p.filtered_r = lp_a0 * output_r - lp_b1 * p.filtered_r;
 		}
 
 		// top end boost
-			boosted_l = bst_a0 * filtered_l - bst_b1 * boosted_l;
+		p.boosted_l = bst_a0 * p.filtered_l - bst_b1 * p.boosted_l;
-			boosted_r = bst_a0 * filtered_r - bst_b1 * boosted_r;
+		p.boosted_r = bst_a0 * p.filtered_r - bst_b1 * p.boosted_r;
-			output_l = filtered_l + (filtered_l - boosted_l) * treble_boost;
+		output_l = p.filtered_l + (p.filtered_l - p.boosted_l) * p.treble_boost;
-			output_r = filtered_r + (filtered_r - boosted_r) * treble_boost;
+		output_r = p.filtered_r + (p.filtered_r - p.boosted_r) * p.treble_boost;
 
 		// calculate makeup gain
-			float makeup_lin = trnr::db_2_lin(-threshold_db / 5.f);
+		float makeup_lin = trnr::db_2_lin(-p.threshold_db / 5.f);
 
 		audio[0][i] = input_l * gain_reduction_lin * makeup_lin;
 		audio[1][i] = input_r * gain_reduction_lin * makeup_lin;
 	}
 }
-
-private:
-	double samplerate;
-	float threshold_db = 0.f;
-	float attack_ms;
-	float release_ms;
-	float hp_filter;
-	float ratio;
-	float filter_frq;
-	float filter_exp;
-	float treble_boost;
-
-	sample filtered;
-	sample filtered_l = 0;
-	sample filtered_r = 0;
-	sample boosted_l = 0;
-	sample boosted_r = 0;
-	float attack_coef;
-	float release_coef;
-	float envelope_db = 0;
-};
 } // namespace trnr