MicroDexed/EngineOpl.cpp

/*
   Copyright (C) 2014  Pascal Gauthier.
   Copyright (C) 2012  Steffen Ohrendorf <steffen.ohrendorf@gmx.de>

   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

   Original Java Code: Copyright (C) 2008 Robson Cozendey <robson@cozendey.com>

   Some code based on forum posts in: http://forums.submarine.org.uk/phpBB/viewforum.php?f=9,
   Copyright (C) 2010-2013 by carbon14 and opl3

*/

#include "EngineOpl.h"

#ifdef _WIN32
__declspec(align(16)) const int zeros[N] = {0};
#else
const int32_t __attribute__ ((aligned(16))) zeros[_N_] = {0};
#endif

uint16_t SignBit = 0x8000;

uint16_t sinLogTable[256] = {
  2137, 1731, 1543, 1419, 1326, 1252, 1190, 1137, 1091, 1050, 1013, 979, 949, 920, 894, 869,
  846, 825, 804, 785, 767, 749, 732, 717, 701, 687, 672, 659, 646, 633, 621, 609,
  598, 587, 576, 566, 556, 546, 536, 527, 518, 509, 501, 492, 484, 476, 468, 461,
  453, 446, 439, 432, 425, 418, 411, 405, 399, 392, 386, 380, 375, 369, 363, 358,
  352, 347, 341, 336, 331, 326, 321, 316, 311, 307, 302, 297, 293, 289, 284, 280,
  276, 271, 267, 263, 259, 255, 251, 248, 244, 240, 236, 233, 229, 226, 222, 219,
  215, 212, 209, 205, 202, 199, 196, 193, 190, 187, 184, 181, 178, 175, 172, 169,
  167, 164, 161, 159, 156, 153, 151, 148, 146, 143, 141, 138, 136, 134, 131, 129,
  127, 125, 122, 120, 118, 116, 114, 112, 110, 108, 106, 104, 102, 100, 98, 96,
  94, 92, 91, 89, 87, 85, 83, 82, 80, 78, 77, 75, 74, 72, 70, 69,
  67, 66, 64, 63, 62, 60, 59, 57, 56, 55, 53, 52, 51, 49, 48, 47,
  46, 45, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30,
  29, 28, 27, 26, 25, 24, 23, 23, 22, 21, 20, 20, 19, 18, 17, 17,
  16, 15, 15, 14, 13, 13, 12, 12, 11, 10, 10, 9, 9, 8, 8, 7,
  7, 7, 6, 6, 5, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2,
  2, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0
};

uint16_t sinExpTable[256] = {
  0, 3, 6, 8, 11, 14, 17, 20, 22, 25, 28, 31, 34, 37, 40, 42,
  45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 90,
  93, 96, 99, 102, 105, 108, 111, 114, 117, 120, 123, 126, 130, 133, 136, 139,
  142, 145, 148, 152, 155, 158, 161, 164, 168, 171, 174, 177, 181, 184, 187, 190,
  194, 197, 200, 204, 207, 210, 214, 217, 220, 224, 227, 231, 234, 237, 241, 244,
  248, 251, 255, 258, 262, 265, 268, 272, 276, 279, 283, 286, 290, 293, 297, 300,
  304, 308, 311, 315, 318, 322, 326, 329, 333, 337, 340, 344, 348, 352, 355, 359,
  363, 367, 370, 374, 378, 382, 385, 389, 393, 397, 401, 405, 409, 412, 416, 420,
  424, 428, 432, 436, 440, 444, 448, 452, 456, 460, 464, 468, 472, 476, 480, 484,
  488, 492, 496, 501, 505, 509, 513, 517, 521, 526, 530, 534, 538, 542, 547, 551,
  555, 560, 564, 568, 572, 577, 581, 585, 590, 594, 599, 603, 607, 612, 616, 621,
  625, 630, 634, 639, 643, 648, 652, 657, 661, 666, 670, 675, 680, 684, 689, 693,
  698, 703, 708, 712, 717, 722, 726, 731, 736, 741, 745, 750, 755, 760, 765, 770,
  774, 779, 784, 789, 794, 799, 804, 809, 814, 819, 824, 829, 834, 839, 844, 849,
  854, 859, 864, 869, 874, 880, 885, 890, 895, 900, 906, 911, 916, 921, 927, 932,
  937, 942, 948, 953, 959, 964, 969, 975, 980, 986, 991, 996, 1002, 1007, 1013, 1018
};

inline uint16_t sinLog(uint16_t phi) {
  const uint8_t index = (phi & 0xff);

  switch ( ( phi & 0x0300 ) ) {
    case 0x0000:
      // rising quarter wave  Shape A
      return sinLogTable[index];
    case 0x0100:
      // falling quarter wave  Shape B
      return sinLogTable[index ^ 0xFF];
    case 0x0200:
      // rising quarter wave -ve  Shape C
      return sinLogTable[index] | SignBit;
    default:
      // falling quarter wave -ve  Shape D
      return sinLogTable[index ^ 0xFF] | SignBit;
  }
}

// 16 env units are ~3dB and halve the output
/**
   @brief OPL Sine Wave calculation
   @param[in] phase Wave phase (0..1023)
   @param[in] env Envelope value (0..511)
   @warning @a env will not be checked for correct values.
*/
inline int16_t oplSin( uint16_t phase, uint16_t env ) {
  uint16_t expVal = sinLog(phase) + (env << 3);
  const bool isSigned = expVal & SignBit;

  expVal &= ~SignBit;
  // expVal: 0..2137+511*8 = 0..6225
  // result: 0..1018+1024
  uint32_t result = 0x0400 + sinExpTable[( expVal & 0xff ) ^ 0xFF];
  result <<= 1;
  result >>= ( expVal >> 8 ); // exp

  if ( isSigned ) {
    // -1 for one's complement
    return -result - 1;
  } else {
    return result;
  }
}

void EngineOpl::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 = oplSin((phase + input[i]) >> 14, gain);
    output[i] = (y << 14) + adder[i];
    phase += freq;
  }

}
void EngineOpl::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 = oplSin(phase >> 14, gain);
    output[i] = (y << 14) + adder[i];
    phase += freq;
  }
}

void EngineOpl::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 = oplSin((phase + scaled_fb) >> 14, gain) << 14;
    output[i] = y + adder[i];
    phase += freq;
  }

  fb_buf[0] = y0;
  fb_buf[1] = y;
}


void EngineOpl::render(int32_t *output, FmOpParams *params, int algorithm, int32_t *fb_buf, int32_t feedback_shift) {
  const int kLevelThresh = 507;  // really ????
  const FmAlgorithm alg = algorithms[algorithm];
  bool has_contents[3] = { true, false, false };
  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 ? 511 : param.gain_out;
    int32_t gain2 = 512 - (param.level_in >> 19);
    param.gain_out = gain2;

    if (gain1 <= kLevelThresh || gain2 <= kLevelThresh) {
      if (!has_contents[outbus]) {
        add = false;
      }
      if (inbus == 0 || !has_contents[inbus]) {
        // todo: more than one op in a feedback loop
        if ((flags & 0xc0) == 0xc0 && feedback_shift < 16) {
          // cout << op << " fb " << inbus << outbus << add << endl;
          compute_fb(outptr, param.phase, param.freq,
                     gain1, gain2,
                     fb_buf, feedback_shift, add);
        } else {
          // cout << op << " pure " << inbus << outbus << add << endl;
          compute_pure(outptr, param.phase, param.freq,
                       gain1, gain2, add);
        }
      } else {
        // cout << op << " normal " << inbus << outbus << " " << param.freq << add << endl;
        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;
  }
}