MicroDexed is a compatible 6-operator-FM-synth based on the Teensy(-3.6/-4.x) Microcontroller. https://www.parasitstudio.de
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/*
Copyright (C) 2015-2017 Pascal Gauthier.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
The code is based on ppplay https://github.com/stohrendorf/ppplay and opl3
math documentation :
https://github.com/gtaylormb/opl3_fpga/blob/master/docs/opl3math/opl3math.pdf
*/
#include "EngineMkI.h"
#define _USE_MATH_DEFINES
#include <cmath>
#include <cstdlib>
#include "sin.h"
#include "exp2.h"
#ifdef DEBUG
#include "time.h"
//#define MKIDEBUG
#endif
#ifdef _WIN32
#if _MSC_VER < 1800
FRAC_NUM log2(FRAC_NUM n) {
//return log(n) / log(2.0);
return LOG_FUNC(n) / LOG_FUNC(2.0);
}
FRAC_NUM round(FRAC_NUM n) {
return n < 0.0 ? ceil(n - 0.5) : floor(n + 0.5);
}
#endif
__declspec(align(16)) const int zeros[N] = {0};
#else
const int32_t __attribute__ ((aligned(16))) zeros[_N_] = {0};
#endif
static const uint16_t NEGATIVE_BIT = 0x8000;
static const uint16_t ENV_BITDEPTH = 14;
static const uint16_t SINLOG_BITDEPTH = 10;
static const uint16_t SINLOG_TABLESIZE = 1 << SINLOG_BITDEPTH;
static uint16_t sinLogTable[SINLOG_TABLESIZE];
static const uint16_t SINEXP_BITDEPTH = 10;
static const uint16_t SINEXP_TABLESIZE = 1 << SINEXP_BITDEPTH;
static uint16_t sinExpTable[SINEXP_TABLESIZE];
const uint16_t ENV_MAX = 1 << ENV_BITDEPTH;
static inline uint16_t sinLog(uint16_t phi) {
const uint16_t SINLOG_TABLEFILTER = SINLOG_TABLESIZE - 1;
const uint16_t index = (phi & SINLOG_TABLEFILTER);
switch ( ( phi & (SINLOG_TABLESIZE * 3) ) ) {
case 0:
return sinLogTable[index];
case SINLOG_TABLESIZE:
return sinLogTable[index ^ SINLOG_TABLEFILTER];
case SINLOG_TABLESIZE * 2 :
return sinLogTable[index] | NEGATIVE_BIT;
default:
return sinLogTable[index ^ SINLOG_TABLEFILTER] | NEGATIVE_BIT;
}
}
EngineMkI::EngineMkI() {
float bitReso = SINLOG_TABLESIZE;
for (int i = 0; i < SINLOG_TABLESIZE; i++) {
//float x1 = sin(((0.5+i)/bitReso) * M_PI/2.0);
float x1 = SIN_FUNC(((0.5 + i) / bitReso) * M_PI / 2.0);
sinLogTable[i] = round(-1024 * log2(x1));
}
bitReso = SINEXP_TABLESIZE;
for (int i = 0; i < SINEXP_TABLESIZE; i++) {
float x1 = (pow(2, float(i) / bitReso) - 1) * 4096;
sinExpTable[i] = round(x1);
}
#ifdef MKIDEBUG
char buffer[4096];
int pos = 0;
for (int i = 0; i < SINLOG_TABLESIZE; i++) {
pos += sprintf(buffer + pos, "%d ", sinLogTable[i]);
if ( pos > 90 ) {
buffer[0] = 0;
pos = 0;
}
}
buffer[0] = 0;
pos = 0;
for (int i = 0; i < SINEXP_TABLESIZE; i++) {
pos += sprintf(buffer + pos, "%d ", sinExpTable[i]);
if ( pos > 90 ) {
buffer[0] = 0;
pos = 0;
}
}
#endif
}
inline int32_t mkiSin(int32_t phase, uint16_t env) {
uint16_t expVal = sinLog(phase >> (22 - SINLOG_BITDEPTH)) + (env);
//int16_t expValShow = expVal;
const bool isSigned = expVal & NEGATIVE_BIT;
expVal &= ~NEGATIVE_BIT;
const uint16_t SINEXP_FILTER = 0x3FF;
uint16_t result = 4096 + sinExpTable[( expVal & SINEXP_FILTER ) ^ SINEXP_FILTER];
//uint16_t resultB4 = result;
result >>= ( expVal >> 10 ); // exp
#ifdef MKIDEBUG
if ( ( time(NULL) % 5 ) == 0 ) {
if ( expValShow < 0 ) {
expValShow = (expValShow + 0x7FFF) * -1;
}
}
#endif
if ( isSigned )
return (-result - 1) << 13;
else
return result << 13;
}
void EngineMkI::compute(int32_t *output, const int32_t *input,
int32_t phase0, int32_t freq,
int32_t gain1, int32_t gain2, bool add) {
int32_t dgain = (gain2 - gain1 + (_N_ >> 1)) >> LG_N;
int32_t gain = gain1;
int32_t phase = phase0;
const int32_t *adder = add ? output : zeros;
for (int i = 0; i < _N_; i++) {
gain += dgain;
int32_t y = mkiSin((phase + input[i]), gain);
output[i] = y + adder[i];
phase += freq;
}
}
void EngineMkI::compute_pure(int32_t *output, int32_t phase0, int32_t freq,
int32_t gain1, int32_t gain2, bool add) {
int32_t dgain = (gain2 - gain1 + (_N_ >> 1)) >> LG_N;
int32_t gain = gain1;
int32_t phase = phase0;
const int32_t *adder = add ? output : zeros;
for (int i = 0; i < _N_; i++) {
gain += dgain;
int32_t y = mkiSin(phase , gain);
output[i] = y + adder[i];
phase += freq;
}
}
void EngineMkI::compute_fb(int32_t *output, int32_t phase0, int32_t freq,
int32_t gain1, int32_t gain2,
int32_t *fb_buf, int fb_shift, bool add) {
int32_t dgain = (gain2 - gain1 + (_N_ >> 1)) >> LG_N;
int32_t gain = gain1;
int32_t phase = phase0;
const int32_t *adder = add ? output : zeros;
int32_t y0 = fb_buf[0];
int32_t y = fb_buf[1];
for (int i = 0; i < _N_; i++) {
gain += dgain;
int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);
y0 = y;
y = mkiSin((phase + scaled_fb), gain);
output[i] = y + adder[i];
phase += freq;
}
fb_buf[0] = y0;
fb_buf[1] = y;
}
// exclusively used for ALGO 6 with feedback
void EngineMkI::compute_fb2(int32_t *output, FmOpParams *parms, int32_t gain01, int32_t gain02, int32_t *fb_buf, int fb_shift) {
int32_t dgain[2];
int32_t gain[2];
int32_t phase[2];
int32_t y0 = fb_buf[0];
int32_t y = fb_buf[1];
phase[0] = parms[0].phase;
phase[1] = parms[1].phase;
parms[1].gain_out = (ENV_MAX - (parms[1].level_in >> (28 - ENV_BITDEPTH)));
gain[0] = gain01;
gain[1] = parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out;
dgain[0] = (gain02 - gain01 + (_N_ >> 1)) >> LG_N;
dgain[1] = (parms[1].gain_out - (parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out));
for (int i = 0; i < _N_; i++) {
int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);
// op 0
gain[0] += dgain[0];
y0 = y;
y = mkiSin(phase[0] + scaled_fb, gain[0]);
phase[0] += parms[0].freq;
// op 1
gain[1] += dgain[1];
y = mkiSin(phase[1] + y, gain[1]);
phase[1] += parms[1].freq;
output[i] = y;
}
fb_buf[0] = y0;
fb_buf[1] = y;
}
// exclusively used for ALGO 4 with feedback
void EngineMkI::compute_fb3(int32_t *output, FmOpParams *parms, int32_t gain01, int32_t gain02, int32_t *fb_buf, int fb_shift) {
int32_t dgain[3];
int32_t gain[3];
int32_t phase[3];
int32_t y0 = fb_buf[0];
int32_t y = fb_buf[1];
phase[0] = parms[0].phase;
phase[1] = parms[1].phase;
phase[2] = parms[2].phase;
parms[1].gain_out = (ENV_MAX - (parms[1].level_in >> (28 - ENV_BITDEPTH)));
parms[2].gain_out = (ENV_MAX - (parms[2].level_in >> (28 - ENV_BITDEPTH)));
gain[0] = gain01;
gain[1] = parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out;
gain[2] = parms[2].gain_out == 0 ? (ENV_MAX - 1) : parms[2].gain_out;
dgain[0] = (gain02 - gain01 + (_N_ >> 1)) >> LG_N;
dgain[1] = (parms[1].gain_out - (parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out));
dgain[2] = (parms[2].gain_out - (parms[2].gain_out == 0 ? (ENV_MAX - 1) : parms[2].gain_out));
for (int i = 0; i < _N_; i++) {
int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);
// op 0
gain[0] += dgain[0];
y0 = y;
y = mkiSin(phase[0] + scaled_fb, gain[0]);
phase[0] += parms[0].freq;
// op 1
gain[1] += dgain[1];
y = mkiSin(phase[1] + y, gain[1]);
phase[1] += parms[1].freq;
// op 2
gain[2] += dgain[2];
y = mkiSin(phase[2] + y, gain[2]);
phase[2] += parms[2].freq;
output[i] = y;
}
fb_buf[0] = y0;
fb_buf[1] = y;
}
void EngineMkI::render(int32_t *output, FmOpParams *params, int algorithm, int32_t *fb_buf, int32_t feedback_shift) {
const int kLevelThresh = ENV_MAX - 100;
FmAlgorithm alg = algorithms[algorithm];
bool has_contents[3] = { true, false, false };
bool fb_on = feedback_shift < 16;
switch (algorithm) {
case 3 : case 5 :
if ( fb_on )
alg.ops[0] = 0xc4;
}
for (int op = 0; op < 6; op++) {
int flags = alg.ops[op];
bool add = (flags & OUT_BUS_ADD) != 0;
FmOpParams &param = params[op];
int inbus = (flags >> 4) & 3;
int outbus = flags & 3;
int32_t *outptr = (outbus == 0) ? output : buf_[outbus - 1].get();
int32_t gain1 = param.gain_out == 0 ? (ENV_MAX - 1) : param.gain_out;
int32_t gain2 = ENV_MAX - (param.level_in >> (28 - ENV_BITDEPTH));
param.gain_out = gain2;
if (gain1 <= kLevelThresh || gain2 <= kLevelThresh) {
if (!has_contents[outbus]) {
add = false;
}
if (inbus == 0 || !has_contents[inbus]) {
// PG: this is my 'dirty' implementation of FB for 2 and 3 operators...
if ((flags & 0xc0) == 0xc0 && fb_on) {
switch ( algorithm ) {
// three operator feedback, process exception for ALGO 4
case 3 :
compute_fb3(outptr, params, gain1, gain2, fb_buf, min((feedback_shift + 2), 16));
params[1].phase += params[1].freq << LG_N; // hack, we already processed op-5 - op-4
params[2].phase += params[2].freq << LG_N; // yuk yuk
op += 2; // ignore the 2 other operators
break;
// two operator feedback, process exception for ALGO 6
case 5 :
compute_fb2(outptr, params, gain1, gain2, fb_buf, min((feedback_shift + 2), 16));
params[1].phase += params[1].freq << LG_N; // yuk, hack, we already processed op-5
op++; // ignore next operator;
break;
default:
// one operator feedback, normal proces
compute_fb(outptr, param.phase, param.freq, gain1, gain2, fb_buf, feedback_shift, add);
break;
}
} else {
compute_pure(outptr, param.phase, param.freq, gain1, gain2, add);
}
} else {
compute(outptr, buf_[inbus - 1].get(), param.phase, param.freq, gain1, gain2, add);
}
has_contents[outbus] = true;
} else if (!add) {
has_contents[outbus] = false;
}
param.phase += param.freq << LG_N;
}
}