MicroDexed/env.cc

/*
 * 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 FRAC_NUM-checked anyway)
};
#endif

void Env::init_sr(FRAC_NUM 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 (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 if (staticcount_) {
            ;
        }
        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_) {
            // approximate number of samples at 44.100 kHz to achieve the time
            // empirically gathered using 2 TF1s, could probably use some FRAC_NUM-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);
            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 ourselve 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_;
}