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+/* Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009 Dean Beeler, Jerome Fisher
+ * Copyright (C) 2011, 2012 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 "mt32emu.h"
+
+#if MT32EMU_USE_REVERBMODEL == 2
+
+#include "BReverbModel.h"
+
+// Analysing of state of reverb RAM address lines gives exact sizes of the buffers of filters used. This also indicates that
+// the reverb model implemented in the real devices consists of three series allpass filters preceded by a non-feedback comb (or a delay with a LPF)
+// and followed by three parallel comb filters
+
+namespace MT32Emu {
+
+// Because LA-32 chip makes it's output available to process by the Boss chip with a significant delay,
+// the Boss chip puts to the buffer the LA32 dry output when it is ready and performs processing of the _previously_ latched data.
+// Of course, the right way would be to use a dedicated variable for this, but our reverb model is way higher level,
+// so we can simply increase the input buffer size.
+static const Bit32u PROCESS_DELAY = 1;
+
+static const Bit32u MODE_3_ADDITIONAL_DELAY = 1;
+static const Bit32u MODE_3_FEEDBACK_DELAY = 1;
+
+// Default reverb settings for modes 0-2. These correspond to CM-32L / LAPC-I "new" reverb settings. MT-32 reverb is a bit different.
+// Found by tracing reverb RAM data lines (thanks go to Lord_Nightmare & balrog).
+
+static const Bit32u MODE_0_NUMBER_OF_ALLPASSES = 3;
+static const Bit32u MODE_0_ALLPASSES[] = {994, 729, 78};
+static const Bit32u MODE_0_NUMBER_OF_COMBS = 4; // Well, actually there are 3 comb filters, but the entrance LPF + delay can be processed via a hacked comb.
+static const Bit32u MODE_0_COMBS[] = {705 + PROCESS_DELAY, 2349, 2839, 3632};
+static const Bit32u MODE_0_OUTL[] = {2349, 141, 1960};
+static const Bit32u MODE_0_OUTR[] = {1174, 1570, 145};
+static const Bit32u MODE_0_COMB_FACTOR[] = {0xA0, 0x60, 0x60, 0x60};
+static const Bit32u MODE_0_COMB_FEEDBACK[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x28, 0x48, 0x60, 0x78, 0x80, 0x88, 0x90, 0x98,
+ 0x28, 0x48, 0x60, 0x78, 0x80, 0x88, 0x90, 0x98,
+ 0x28, 0x48, 0x60, 0x78, 0x80, 0x88, 0x90, 0x98};
+static const Bit32u MODE_0_DRY_AMP[] = {0xA0, 0xA0, 0xA0, 0xA0, 0xB0, 0xB0, 0xB0, 0xD0};
+static const Bit32u MODE_0_WET_AMP[] = {0x10, 0x30, 0x50, 0x70, 0x90, 0xC0, 0xF0, 0xF0};
+static const Bit32u MODE_0_LPF_AMP = 0x60;
+
+static const Bit32u MODE_1_NUMBER_OF_ALLPASSES = 3;
+static const Bit32u MODE_1_ALLPASSES[] = {1324, 809, 176};
+static const Bit32u MODE_1_NUMBER_OF_COMBS = 4; // Same as for mode 0 above
+static const Bit32u MODE_1_COMBS[] = {961 + PROCESS_DELAY, 2619, 3545, 4519};
+static const Bit32u MODE_1_OUTL[] = {2618, 1760, 4518};
+static const Bit32u MODE_1_OUTR[] = {1300, 3532, 2274};
+static const Bit32u MODE_1_COMB_FACTOR[] = {0x80, 0x60, 0x60, 0x60};
+static const Bit32u MODE_1_COMB_FEEDBACK[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x28, 0x48, 0x60, 0x70, 0x78, 0x80, 0x90, 0x98,
+ 0x28, 0x48, 0x60, 0x78, 0x80, 0x88, 0x90, 0x98,
+ 0x28, 0x48, 0x60, 0x78, 0x80, 0x88, 0x90, 0x98};
+static const Bit32u MODE_1_DRY_AMP[] = {0xA0, 0xA0, 0xB0, 0xB0, 0xB0, 0xB0, 0xB0, 0xE0};
+static const Bit32u MODE_1_WET_AMP[] = {0x10, 0x30, 0x50, 0x70, 0x90, 0xC0, 0xF0, 0xF0};
+static const Bit32u MODE_1_LPF_AMP = 0x60;
+
+static const Bit32u MODE_2_NUMBER_OF_ALLPASSES = 3;
+static const Bit32u MODE_2_ALLPASSES[] = {969, 644, 157};
+static const Bit32u MODE_2_NUMBER_OF_COMBS = 4; // Same as for mode 0 above
+static const Bit32u MODE_2_COMBS[] = {116 + PROCESS_DELAY, 2259, 2839, 3539};
+static const Bit32u MODE_2_OUTL[] = {2259, 718, 1769};
+static const Bit32u MODE_2_OUTR[] = {1136, 2128, 1};
+static const Bit32u MODE_2_COMB_FACTOR[] = {0, 0x20, 0x20, 0x20};
+static const Bit32u MODE_2_COMB_FEEDBACK[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x30, 0x58, 0x78, 0x88, 0xA0, 0xB8, 0xC0, 0xD0,
+ 0x30, 0x58, 0x78, 0x88, 0xA0, 0xB8, 0xC0, 0xD0,
+ 0x30, 0x58, 0x78, 0x88, 0xA0, 0xB8, 0xC0, 0xD0};
+static const Bit32u MODE_2_DRY_AMP[] = {0xA0, 0xA0, 0xB0, 0xB0, 0xB0, 0xB0, 0xC0, 0xE0};
+static const Bit32u MODE_2_WET_AMP[] = {0x10, 0x30, 0x50, 0x70, 0x90, 0xC0, 0xF0, 0xF0};
+static const Bit32u MODE_2_LPF_AMP = 0x80;
+
+static const Bit32u MODE_3_NUMBER_OF_ALLPASSES = 0;
+static const Bit32u MODE_3_NUMBER_OF_COMBS = 1;
+static const Bit32u MODE_3_DELAY[] = {16000 + MODE_3_FEEDBACK_DELAY + PROCESS_DELAY + MODE_3_ADDITIONAL_DELAY};
+static const Bit32u MODE_3_OUTL[] = {400, 624, 960, 1488, 2256, 3472, 5280, 8000};
+static const Bit32u MODE_3_OUTR[] = {800, 1248, 1920, 2976, 4512, 6944, 10560, 16000};
+static const Bit32u MODE_3_COMB_FACTOR[] = {0x68};
+static const Bit32u MODE_3_COMB_FEEDBACK[] = {0x68, 0x60};
+static const Bit32u MODE_3_DRY_AMP[] = {0x20, 0x50, 0x50, 0x50, 0x50, 0x50, 0x50, 0x50};
+static const Bit32u MODE_3_WET_AMP[] = {0x18, 0x18, 0x28, 0x40, 0x60, 0x80, 0xA8, 0xF8};
+
+static const BReverbSettings REVERB_MODE_0_SETTINGS = {MODE_0_NUMBER_OF_ALLPASSES, MODE_0_ALLPASSES, MODE_0_NUMBER_OF_COMBS, MODE_0_COMBS, MODE_0_OUTL, MODE_0_OUTR, MODE_0_COMB_FACTOR, MODE_0_COMB_FEEDBACK, MODE_0_DRY_AMP, MODE_0_WET_AMP, MODE_0_LPF_AMP};
+static const BReverbSettings REVERB_MODE_1_SETTINGS = {MODE_1_NUMBER_OF_ALLPASSES, MODE_1_ALLPASSES, MODE_1_NUMBER_OF_COMBS, MODE_1_COMBS, MODE_1_OUTL, MODE_1_OUTR, MODE_1_COMB_FACTOR, MODE_1_COMB_FEEDBACK, MODE_1_DRY_AMP, MODE_1_WET_AMP, MODE_1_LPF_AMP};
+static const BReverbSettings REVERB_MODE_2_SETTINGS = {MODE_2_NUMBER_OF_ALLPASSES, MODE_2_ALLPASSES, MODE_2_NUMBER_OF_COMBS, MODE_2_COMBS, MODE_2_OUTL, MODE_2_OUTR, MODE_2_COMB_FACTOR, MODE_2_COMB_FEEDBACK, MODE_2_DRY_AMP, MODE_2_WET_AMP, MODE_2_LPF_AMP};
+static const BReverbSettings REVERB_MODE_3_SETTINGS = {MODE_3_NUMBER_OF_ALLPASSES, NULL, MODE_3_NUMBER_OF_COMBS, MODE_3_DELAY, MODE_3_OUTL, MODE_3_OUTR, MODE_3_COMB_FACTOR, MODE_3_COMB_FEEDBACK, MODE_3_DRY_AMP, MODE_3_WET_AMP, 0};
+
+static const BReverbSettings * const REVERB_SETTINGS[] = {&REVERB_MODE_0_SETTINGS, &REVERB_MODE_1_SETTINGS, &REVERB_MODE_2_SETTINGS, &REVERB_MODE_3_SETTINGS};
+
+// This algorithm tries to emulate exactly Boss multiplication operation (at least this is what we see on reverb RAM data lines).
+// Also LA32 is suspected to use the similar one to perform PCM interpolation and ring modulation.
+static Bit32s weirdMul(Bit32s a, Bit8u addMask, Bit8u carryMask) {
+ Bit8u mask = 0x80;
+ Bit32s res = 0;
+ for (int i = 0; i < 8; i++) {
+ Bit32s carry = (a < 0) && (mask & carryMask) > 0 ? a & 1 : 0;
+ a >>= 1;
+ res += (mask & addMask) > 0 ? a + carry : 0;
+ mask >>= 1;
+ }
+ return res;
+}
+
+RingBuffer::RingBuffer(Bit32u newsize) : size(newsize), index(0) {
+ buffer = new Bit16s[size];
+}
+
+RingBuffer::~RingBuffer() {
+ delete[] buffer;
+ buffer = NULL;
+}
+
+Bit32s RingBuffer::next() {
+ if (++index >= size) {
+ index = 0;
+ }
+ return buffer[index];
+}
+
+bool RingBuffer::isEmpty() const {
+ if (buffer == NULL) return true;
+
+ Bit16s *buf = buffer;
+ for (Bit32u i = 0; i < size; i++) {
+ if (*buf < -8 || *buf > 8) return false;
+ buf++;
+ }
+ return true;
+}
+
+void RingBuffer::mute() {
+ Bit16s *buf = buffer;
+ for (Bit32u i = 0; i < size; i++) {
+ *buf++ = 0;
+ }
+}
+
+AllpassFilter::AllpassFilter(const Bit32u useSize) : RingBuffer(useSize) {}
+
+Bit32s AllpassFilter::process(const Bit32s in) {
+ // This model corresponds to the allpass filter implementation of the real CM-32L device
+ // found from sample analysis
+
+ Bit16s bufferOut = next();
+
+ // store input - feedback / 2
+ buffer[index] = in - (bufferOut >> 1);
+
+ // return buffer output + feedforward / 2
+ return bufferOut + (buffer[index] >> 1);
+}
+
+CombFilter::CombFilter(const Bit32u useSize, const Bit32u useFilterFactor) : RingBuffer(useSize), filterFactor(useFilterFactor) {}
+
+void CombFilter::process(const Bit32s in) {
+ // This model corresponds to the comb filter implementation of the real CM-32L device
+
+ // the previously stored value
+ Bit32s last = buffer[index];
+
+ // prepare input + feedback
+ Bit32s filterIn = in + weirdMul(next(), feedbackFactor, 0xF0 /* Maybe 0x80 ? */);
+
+ // store input + feedback processed by a low-pass filter
+ buffer[index] = weirdMul(last, filterFactor, 0x40) - filterIn;
+}
+
+Bit32s CombFilter::getOutputAt(const Bit32u outIndex) const {
+ return buffer[(size + index - outIndex) % size];
+}
+
+void CombFilter::setFeedbackFactor(const Bit32u useFeedbackFactor) {
+ feedbackFactor = useFeedbackFactor;
+}
+
+DelayWithLowPassFilter::DelayWithLowPassFilter(const Bit32u useSize, const Bit32u useFilterFactor, const Bit32u useAmp)
+ : CombFilter(useSize, useFilterFactor), amp(useAmp) {}
+
+void DelayWithLowPassFilter::process(const Bit32s in) {
+ // the previously stored value
+ Bit32s last = buffer[index];
+
+ // move to the next index
+ next();
+
+ // low-pass filter process
+ Bit32s lpfOut = weirdMul(last, filterFactor, 0xFF) + in;
+
+ // store lpfOut multiplied by LPF amp factor
+ buffer[index] = weirdMul(lpfOut, amp, 0xFF);
+}
+
+TapDelayCombFilter::TapDelayCombFilter(const Bit32u useSize, const Bit32u useFilterFactor) : CombFilter(useSize, useFilterFactor) {}
+
+void TapDelayCombFilter::process(const Bit32s in) {
+ // the previously stored value
+ Bit32s last = buffer[index];
+
+ // move to the next index
+ next();
+
+ // prepare input + feedback
+ // Actually, the size of the filter varies with the TIME parameter, the feedback sample is taken from the position just below the right output
+ Bit32s filterIn = in + weirdMul(getOutputAt(outR + MODE_3_FEEDBACK_DELAY), feedbackFactor, 0xF0);
+
+ // store input + feedback processed by a low-pass filter
+ buffer[index] = weirdMul(last, filterFactor, 0xF0) - filterIn;
+}
+
+Bit32s TapDelayCombFilter::getLeftOutput() const {
+ return getOutputAt(outL + PROCESS_DELAY + MODE_3_ADDITIONAL_DELAY);
+}
+
+Bit32s TapDelayCombFilter::getRightOutput() const {
+ return getOutputAt(outR + PROCESS_DELAY + MODE_3_ADDITIONAL_DELAY);
+}
+
+void TapDelayCombFilter::setOutputPositions(const Bit32u useOutL, const Bit32u useOutR) {
+ outL = useOutL;
+ outR = useOutR;
+}
+
+BReverbModel::BReverbModel(const ReverbMode mode)
+ : allpasses(NULL), combs(NULL), currentSettings(*REVERB_SETTINGS[mode]), tapDelayMode(mode == REVERB_MODE_TAP_DELAY) {}
+
+BReverbModel::~BReverbModel() {
+ close();
+}
+
+void BReverbModel::open() {
+ if (currentSettings.numberOfAllpasses > 0) {
+ allpasses = new AllpassFilter*[currentSettings.numberOfAllpasses];
+ for (Bit32u i = 0; i < currentSettings.numberOfAllpasses; i++) {
+ allpasses[i] = new AllpassFilter(currentSettings.allpassSizes[i]);
+ }
+ }
+ combs = new CombFilter*[currentSettings.numberOfCombs];
+ if (tapDelayMode) {
+ *combs = new TapDelayCombFilter(*currentSettings.combSizes, *currentSettings.filterFactors);
+ } else {
+ combs[0] = new DelayWithLowPassFilter(currentSettings.combSizes[0], currentSettings.filterFactors[0], currentSettings.lpfAmp);
+ for (Bit32u i = 1; i < currentSettings.numberOfCombs; i++) {
+ combs[i] = new CombFilter(currentSettings.combSizes[i], currentSettings.filterFactors[i]);
+ }
+ }
+ mute();
+}
+
+void BReverbModel::close() {
+ if (allpasses != NULL) {
+ for (Bit32u i = 0; i < currentSettings.numberOfAllpasses; i++) {
+ if (allpasses[i] != NULL) {
+ delete allpasses[i];
+ allpasses[i] = NULL;
+ }
+ }
+ delete[] allpasses;
+ allpasses = NULL;
+ }
+ if (combs != NULL) {
+ for (Bit32u i = 0; i < currentSettings.numberOfCombs; i++) {
+ if (combs[i] != NULL) {
+ delete combs[i];
+ combs[i] = NULL;
+ }
+ }
+ delete[] combs;
+ combs = NULL;
+ }
+}
+
+void BReverbModel::mute() {
+ if (allpasses != NULL) {
+ for (Bit32u i = 0; i < currentSettings.numberOfAllpasses; i++) {
+ allpasses[i]->mute();
+ }
+ }
+ if (combs != NULL) {
+ for (Bit32u i = 0; i < currentSettings.numberOfCombs; i++) {
+ combs[i]->mute();
+ }
+ }
+}
+
+void BReverbModel::setParameters(Bit8u time, Bit8u level) {
+ if (combs == NULL) return;
+ level &= 7;
+ time &= 7;
+ if (tapDelayMode) {
+ TapDelayCombFilter *comb = static_cast<TapDelayCombFilter *> (*combs);
+ comb->setOutputPositions(currentSettings.outLPositions[time], currentSettings.outRPositions[time & 7]);
+ comb->setFeedbackFactor(currentSettings.feedbackFactors[((level < 3) || (time < 6)) ? 0 : 1]);
+ } else {
+ for (Bit32u i = 0; i < currentSettings.numberOfCombs; i++) {
+ combs[i]->setFeedbackFactor(currentSettings.feedbackFactors[(i << 3) + time]);
+ }
+ }
+ if (time == 0 && level == 0) {
+ dryAmp = wetLevel = 0;
+ } else {
+ dryAmp = currentSettings.dryAmps[level];
+ wetLevel = currentSettings.wetLevels[level];
+ }
+}
+
+bool BReverbModel::isActive() const {
+ for (Bit32u i = 0; i < currentSettings.numberOfAllpasses; i++) {
+ if (!allpasses[i]->isEmpty()) return true;
+ }
+ for (Bit32u i = 0; i < currentSettings.numberOfCombs; i++) {
+ if (!combs[i]->isEmpty()) return true;
+ }
+ return false;
+}
+
+void BReverbModel::process(const float *inLeft, const float *inRight, float *outLeft, float *outRight, unsigned long numSamples) {
+ Bit32s dry, link, outL1, outR1;
+
+ for (unsigned long i = 0; i < numSamples; i++) {
+ if (tapDelayMode) {
+ dry = Bit32s(*inLeft * 8192.0f) + Bit32s(*inRight * 8192.0f);
+ } else {
+ dry = Bit32s(*inLeft * 8192.0f) / 2 + Bit32s(*inRight * 8192.0f) / 2;
+ }
+
+ // Looks like dryAmp doesn't change in MT-32 but it does in CM-32L / LAPC-I
+ dry = weirdMul(dry, dryAmp, 0xFF);
+
+ if (tapDelayMode) {
+ TapDelayCombFilter *comb = static_cast<TapDelayCombFilter *> (*combs);
+ comb->process(dry);
+ *outLeft = weirdMul(comb->getLeftOutput(), wetLevel, 0xFF) / 8192.0f;
+ *outRight = weirdMul(comb->getRightOutput(), wetLevel, 0xFF) / 8192.0f;
+ } else {
+ // Get the last stored sample before processing in order not to loose it
+ link = combs[0]->getOutputAt(currentSettings.combSizes[0] - 1);
+
+ // Entrance LPF. Note, comb.process() differs a bit here.
+ combs[0]->process(dry);
+
+ // This introduces reverb noise which actually makes output from the real Boss chip nondeterministic
+ link = link - 1;
+ link = allpasses[0]->process(link);
+ link = allpasses[1]->process(link);
+ link = allpasses[2]->process(link);
+
+ // If the output position is equal to the comb size, get it now in order not to loose it
+ outL1 = combs[1]->getOutputAt(currentSettings.outLPositions[0] - 1);
+ outL1 += outL1 >> 1;
+
+ combs[1]->process(link);
+ combs[2]->process(link);
+ combs[3]->process(link);
+
+ link = combs[2]->getOutputAt(currentSettings.outLPositions[1]);
+ link += link >> 1;
+ link += outL1;
+ link += combs[3]->getOutputAt(currentSettings.outLPositions[2]);
+ *outLeft = weirdMul(link, wetLevel, 0xFF) / 8192.0f;
+
+ outR1 = combs[1]->getOutputAt(currentSettings.outRPositions[0]);
+ outR1 += outR1 >> 1;
+ link = combs[2]->getOutputAt(currentSettings.outRPositions[1]);
+ link += link >> 1;
+ link += outR1;
+ link += combs[3]->getOutputAt(currentSettings.outRPositions[2]);
+ *outRight = weirdMul(link, wetLevel, 0xFF) / 8192.0f;
+ }
+
+ inLeft++;
+ inRight++;
+ outLeft++;
+ outRight++;
+ }
+}
+
+}
+
+#endif
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