MicroDexed/env.cpp

/*
   Copyright 2017 Pascal Gauthier.
   Copyright 2012 Google Inc.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

#include <math.h>

#include "synth.h"
#include "env.h"

//using namespace std;

uint32_t Env::sr_multiplier = (1 << 24);

const int levellut[] = {
  0, 5, 9, 13, 17, 20, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 42, 43, 45, 46
};

#ifdef ACCURATE_ENVELOPE
const int statics[] = {
  1764000, 1764000, 1411200, 1411200, 1190700, 1014300, 992250,
  882000, 705600, 705600, 584325, 507150, 502740, 441000, 418950,
  352800, 308700, 286650, 253575, 220500, 220500, 176400, 145530,
  145530, 125685, 110250, 110250, 88200, 88200, 74970, 61740,
  61740, 55125, 48510, 44100, 37485, 31311, 30870, 27562, 27562,
  22050, 18522, 17640, 15435, 14112, 13230, 11025, 9261, 9261, 7717,
  6615, 6615, 5512, 5512, 4410, 3969, 3969, 3439, 2866, 2690, 2249,
  1984, 1896, 1808, 1411, 1367, 1234, 1146, 926, 837, 837, 705,
  573, 573, 529, 441, 441
  // and so on, I stopped measuring after R=76 (needs to be double-checked anyway)
};
#endif

void Env::init_sr(double sampleRate) {
  sr_multiplier = (44100.0 / sampleRate) * (1 << 24);
}

void Env::init(const int r[4], const int l[4], int ol, int rate_scaling) {
  for (int i = 0; i < 4; i++) {
    rates_[i] = r[i];
    levels_[i] = l[i];
  }
  outlevel_ = ol;
  rate_scaling_ = rate_scaling;
  level_ = 0;
  down_ = true;
  advance(0);
}

int32_t Env::getsample() {
#ifdef ACCURATE_ENVELOPE
  if (staticcount_) {
    staticcount_ -= _N_;
    if (staticcount_ <= 0) {
      staticcount_ = 0;
      advance(ix_ + 1);
    }
  }
#endif

  if (ix_ < 3 || ((ix_ < 4) && !down_)) {
    if (staticcount_) {
      ;
    }
    else if (rising_) {
      const int jumptarget = 1716;
      if (level_ < (jumptarget << 16)) {
        level_ = jumptarget << 16;
      }
      level_ += (((17 << 24) - level_) >> 24) * inc_;
      // TODO: should probably be more accurate when inc is large
      if (level_ >= targetlevel_) {
        level_ = targetlevel_;
        advance(ix_ + 1);
      }
    }
    else {  // !rising
      level_ -= inc_;
      if (level_ <= targetlevel_) {
        level_ = targetlevel_;
        advance(ix_ + 1);
      }
    }
  }
  // TODO: this would be a good place to set level to 0 when under threshold
  return level_;
}

void Env::keydown(bool d) {
  if (down_ != d) {
    down_ = d;
    advance(d ? 0 : 3);
  }
}

int Env::scaleoutlevel(int outlevel) {
  return outlevel >= 20 ? 28 + outlevel : levellut[outlevel];
}

void Env::advance(int newix) {
  ix_ = newix;
  if (ix_ < 4) {
    int newlevel = levels_[ix_];
    int actuallevel = scaleoutlevel(newlevel) >> 1;
    actuallevel = (actuallevel << 6) + outlevel_ - 4256;
    actuallevel = actuallevel < 16 ? 16 : actuallevel;
    // level here is same as Java impl
    targetlevel_ = actuallevel << 16;
    rising_ = (targetlevel_ > level_);

    // rate
    int qrate = (rates_[ix_] * 41) >> 6;
    qrate += rate_scaling_;
    qrate = min(qrate, 63);

#ifdef ACCURATE_ENVELOPE
    if (targetlevel_ == level_ || (ix_ == 0 && newlevel == 0)) {
      // approximate number of samples at 44.100 kHz to achieve the time
      // empirically gathered using 2 TF1s, could probably use some double-checking
      // and cleanup, but it's pretty close for now.
      int staticrate = rates_[ix_];
      staticrate += rate_scaling_; // needs to be checked, as well, but seems correct
      staticrate = min(staticrate, 99);
      staticcount_ = staticrate < 77 ? statics[staticrate] : 20 * (99 - staticrate);
      if (staticrate < 77 && (ix_ == 0 && newlevel == 0)) {
        staticcount_ /= 20; // attack is scaled faster
      }
      staticcount_ = (int)(((int64_t)staticcount_ * (int64_t)sr_multiplier) >> 24);
    }
    else {
      staticcount_ = 0;
    }
#endif
    inc_ = (4 + (qrate & 3)) << (2 + LG_N + (qrate >> 2));
    // meh, this should be fixed elsewhere
    inc_ = (int)(((int64_t)inc_ * (int64_t)sr_multiplier) >> 24);
  }
}

void Env::update(const int r[4], const int l[4], int ol, int rate_scaling) {
  for (int i = 0; i < 4; i++) {
    rates_[i] = r[i];
    levels_[i] = l[i];
  }
  outlevel_ = ol;
  rate_scaling_ = rate_scaling;
  if ( down_ ) {
    // for now we simply reset ourselves at level 3
    int newlevel = levels_[2];
    int actuallevel = scaleoutlevel(newlevel) >> 1;
    actuallevel = (actuallevel << 6) - 4256;
    actuallevel = actuallevel < 16 ? 16 : actuallevel;
    targetlevel_ = actuallevel << 16;
    advance(2);
  }
}

void Env::getPosition(char *step) {
  *step = ix_;
}

void Env::transfer(Env &src) {
  for (int i = 0; i < 4; i++) {
    rates_[i] = src.rates_[i];
    levels_[i] = src.levels_[i];
  }
  outlevel_ = src.outlevel_;
  rate_scaling_ = src.rate_scaling_;
  level_ = src.level_;
  targetlevel_ = src.targetlevel_;
  rising_ = src.rising_;
  ix_ = src.ix_;
  down_ = src.down_;
#ifdef ACCURATE_ENVELOPE
  staticcount_ = src.staticcount_;
#endif
  inc_ = src.inc_;
}