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diff --git a/audio/softsynth/mt32/TVF.cpp b/audio/softsynth/mt32/TVF.cpp
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+++ b/audio/softsynth/mt32/TVF.cpp
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+/* Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009 Dean Beeler, Jerome Fisher
+ * Copyright (C) 2011 Dean Beeler, Jerome Fisher, Sergey V. Mikayev
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Lesser General Public License as published by
+ *  the Free Software Foundation, either version 2.1 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+//#include <cmath>
+
+#include "mt32emu.h"
+#include "mmath.h"
+
+namespace MT32Emu {
+
+// Note that when entering nextPhase(), newPhase is set to phase + 1, and the descriptions/names below refer to
+// newPhase's value.
+enum {
+	// When this is the target phase, level[0] is targeted within time[0]
+	// Note that this phase is always set up in reset(), not nextPhase()
+	PHASE_ATTACK = 1,
+
+	// When this is the target phase, level[1] is targeted within time[1]
+	PHASE_2 = 2,
+
+	// When this is the target phase, level[2] is targeted within time[2]
+	PHASE_3 = 3,
+
+	// When this is the target phase, level[3] is targeted within time[3]
+	PHASE_4 = 4,
+
+	// When this is the target phase, immediately goes to PHASE_RELEASE unless the poly is set to sustain.
+	// Otherwise level[3] is continued with increment 0 - no phase change will occur until some external influence (like pedal release)
+	PHASE_SUSTAIN = 5,
+
+	// 0 is targeted within time[4] (the time calculation is quite different from the other phases)
+	PHASE_RELEASE = 6,
+
+	// 0 is targeted with increment 0 (thus theoretically staying that way forever)
+	PHASE_DONE = 7
+};
+
+static int calcBaseCutoff(const TimbreParam::PartialParam *partialParam, Bit32u basePitch, unsigned int key) {
+	// This table matches the values used by a real LAPC-I.
+	static const Bit8s biasLevelToBiasMult[] = {85, 42, 21, 16, 10, 5, 2, 0, -2, -5, -10, -16, -21, -74, -85};
+	// These values represent unique options with no consistent pattern, so we have to use something like a table in any case.
+	// The table entries, when divided by 21, match approximately what the manual claims:
+	// -1, -1/2, -1/4, 0, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8, 1, 5/4, 3/2, 2, s1, s2
+	// Note that the entry for 1/8 is rounded to 2 (from 1/8 * 21 = 2.625), which seems strangely inaccurate compared to the others.
+	static const Bit8s keyfollowMult21[] = {-21, -10, -5, 0, 2, 5, 8, 10, 13, 16, 18, 21, 26, 32, 42, 21, 21};
+	int baseCutoff = keyfollowMult21[partialParam->tvf.keyfollow] - keyfollowMult21[partialParam->wg.pitchKeyfollow];
+	// baseCutoff range now: -63 to 63
+	baseCutoff *= (int)key - 60;
+	// baseCutoff range now: -3024 to 3024
+	int biasPoint = partialParam->tvf.biasPoint;
+	if ((biasPoint & 0x40) == 0) {
+		// biasPoint range here: 0 to 63
+		int bias = biasPoint + 33 - key; // bias range here: -75 to 84 
+		if (bias > 0) {
+			bias = -bias; // bias range here: -1 to -84
+			baseCutoff += bias * biasLevelToBiasMult[partialParam->tvf.biasLevel]; // Calculation range: -7140 to 7140
+			// baseCutoff range now: -10164 to 10164 
+		}
+	} else {
+		// biasPoint range here: 64 to 127
+		int bias = biasPoint - 31 - key; // bias range here: -75 to 84
+		if (bias < 0) {
+			baseCutoff += bias * biasLevelToBiasMult[partialParam->tvf.biasLevel]; // Calculation range: −6375 to 6375
+			// baseCutoff range now: -9399 to 9399
+		}
+	}
+	// baseCutoff range now: -10164 to 10164
+	baseCutoff += ((partialParam->tvf.cutoff << 4) - 800);
+	// baseCutoff range now: -10964 to 10964
+	if (baseCutoff >= 0) {
+		// FIXME: Potentially bad if baseCutoff ends up below -2056?
+		int pitchDeltaThing = (basePitch >> 4) + baseCutoff - 3584;
+		if (pitchDeltaThing > 0) {
+			baseCutoff -= pitchDeltaThing;
+		}
+	} else if (baseCutoff < -2048) {
+		baseCutoff = -2048;
+	}
+	baseCutoff += 2056;
+	baseCutoff >>= 4; // PORTABILITY NOTE: Hmm... Depends whether it could've been below -2056, but maybe arithmetic shift assumed?
+	if (baseCutoff > 255) {
+		baseCutoff = 255;
+	}
+	return (Bit8u)baseCutoff;
+}
+
+TVF::TVF(const Partial *usePartial, LA32Ramp *useCutoffModifierRamp) :
+	partial(usePartial), cutoffModifierRamp(useCutoffModifierRamp) {
+}
+
+void TVF::startRamp(Bit8u newTarget, Bit8u newIncrement, int newPhase) {
+	target = newTarget;
+	phase = newPhase;
+	cutoffModifierRamp->startRamp(newTarget, newIncrement);
+#if MT32EMU_MONITOR_TVF >= 1
+	partial->getSynth()->printDebug("[+%lu] [Partial %d] TVF,ramp,%d,%d,%d,%d", partial->debugGetSampleNum(), partial->debugGetPartialNum(), newTarget, (newIncrement & 0x80) ? -1 : 1, (newIncrement & 0x7F), newPhase);
+#endif
+}
+
+void TVF::reset(const TimbreParam::PartialParam *newPartialParam, unsigned int basePitch) {
+	partialParam = newPartialParam;
+
+	unsigned int key = partial->getPoly()->getKey();
+	unsigned int velocity = partial->getPoly()->getVelocity();
+
+	Tables *tables = &partial->getSynth()->tables;
+
+	baseCutoff = calcBaseCutoff(newPartialParam, basePitch, key);
+#if MT32EMU_MONITOR_TVF >= 1
+	partial->getSynth()->printDebug("[+%lu] [Partial %d] TVF,base,%d", partial->debugGetSampleNum(), partial->debugGetPartialNum(), baseCutoff);
+#endif
+
+	int newLevelMult = velocity * newPartialParam->tvf.envVeloSensitivity;
+	newLevelMult >>= 6;
+	newLevelMult += 109 - newPartialParam->tvf.envVeloSensitivity;
+	newLevelMult += ((signed)key - 60) >> (4 - newPartialParam->tvf.envDepthKeyfollow);
+	if (newLevelMult < 0) {
+		newLevelMult = 0;
+	}
+	newLevelMult *= newPartialParam->tvf.envDepth;
+	newLevelMult >>= 6;
+	if (newLevelMult > 255) {
+		newLevelMult = 255;
+	}
+	levelMult = newLevelMult;
+
+	if (newPartialParam->tvf.envTimeKeyfollow != 0) {
+		keyTimeSubtraction = ((signed)key - 60) >> (5 - newPartialParam->tvf.envTimeKeyfollow);
+	} else {
+		keyTimeSubtraction = 0;
+	}
+
+	int newTarget = (newLevelMult * newPartialParam->tvf.envLevel[0]) >> 8;
+	int envTimeSetting = newPartialParam->tvf.envTime[0] - keyTimeSubtraction;
+	int newIncrement;
+	if (envTimeSetting <= 0) {
+		newIncrement = (0x80 | 127);
+	} else {
+		newIncrement = tables->envLogarithmicTime[newTarget] - envTimeSetting;
+		if (newIncrement <= 0) {
+			newIncrement = 1;
+		}
+	}
+	cutoffModifierRamp->reset();
+	startRamp(newTarget, newIncrement, PHASE_2 - 1);
+}
+
+Bit8u TVF::getBaseCutoff() const {
+	return baseCutoff;
+}
+
+void TVF::handleInterrupt() {
+	nextPhase();
+}
+
+void TVF::startDecay() {
+	if (phase >= PHASE_RELEASE) {
+		return;
+	}
+	if (partialParam->tvf.envTime[4] == 0) {
+		startRamp(0, 1, PHASE_DONE - 1);
+	} else {
+		startRamp(0, -partialParam->tvf.envTime[4], PHASE_DONE - 1);
+	}
+}
+
+void TVF::nextPhase() {
+	Tables *tables = &partial->getSynth()->tables;
+	int newPhase = phase + 1;
+
+	switch (newPhase) {
+	case PHASE_DONE:
+		startRamp(0, 0, newPhase);
+		return;
+	case PHASE_SUSTAIN:
+	case PHASE_RELEASE:
+		// FIXME: Afaict newPhase should never be PHASE_RELEASE here. And if it were, this is an odd way to handle it.
+		if (!partial->getPoly()->canSustain()) {
+			phase = newPhase; // FIXME: Correct?
+			startDecay(); // FIXME: This should actually start decay even if phase is already 6. Does that matter?
+			return;
+		}
+		startRamp((levelMult * partialParam->tvf.envLevel[3]) >> 8, 0, newPhase);
+		return;
+	}
+
+	int envPointIndex = phase;
+	int envTimeSetting = partialParam->tvf.envTime[envPointIndex] - keyTimeSubtraction;
+
+	int newTarget = (levelMult * partialParam->tvf.envLevel[envPointIndex]) >> 8;
+	int newIncrement;
+	if (envTimeSetting > 0) {
+		int targetDelta = newTarget - target;
+		if (targetDelta == 0) {
+			if (newTarget == 0) {
+				targetDelta = 1;
+				newTarget = 1;
+			} else {
+				targetDelta = -1;
+				newTarget--;
+			}
+		}
+		newIncrement = tables->envLogarithmicTime[targetDelta < 0 ? -targetDelta : targetDelta] - envTimeSetting;
+		if (newIncrement <= 0) {
+			newIncrement = 1;
+		}
+		if (targetDelta < 0) {
+			newIncrement |= 0x80;
+		}
+	} else {
+		newIncrement = newTarget >= target ? (0x80 | 127) : 127;
+	}
+	startRamp(newTarget, newIncrement, newPhase);
+}
+
+}