ss_eff.c

   1 /*
   2
   3     Ann Hell Ex Machina - Music Software
   4     Copyright (C) 2003/2006 Angel Ortega <angel@triptico.com>
   5
   6     ss_eff.c - Software syntesizer's digital effects
   7
   8     This program is free software; you can redistribute it and/or
   9     modify it under the terms of the GNU General Public License
  10     as published by the Free Software Foundation; either version 2
  11     of the License, or (at your option) any later version.
  12
  13     This program is distributed in the hope that it will be useful,
  14     but WITHOUT ANY WARRANTY; without even the implied warranty of
  15     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16     GNU General Public License for more details.
  17
  18     You should have received a copy of the GNU General Public License
  19     along with this program; if not, write to the Free Software
  20     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21
  22     http://www.triptico.com
  23
  24 */
  25
  26 #include "config.h"
  27
  28 #include <stdio.h>
  29 #include <string.h>
  30 #include <stdlib.h>
  31 #include <math.h>
  32
  33 #include "ahxm.h"
  34
  35 /*******************
  36         Data
  37 ********************/
  38
  39 /*******************
  40         Code
  41 ********************/
  42
  43 static struct ss_eff * ss_eff_add(struct ss_eff ** ec, double size,
  44         sample_t gain, sample_t (* func)(struct ss_eff *, sample_t))
  45 /* adds an effect to the ec chain */
  46 {
  47         struct ss_eff * e;
  48
  49         /* convert to frames */
  50         size = MS2F(size);
  51
  52         /* create new structure and reset */
  53         if((e = malloc(sizeof(struct ss_eff))) == NULL)
  54                 return(NULL);
  55
  56         memset(e, '\0', sizeof(struct ss_eff));
  57
  58         /* enqueue */
  59         if(*ec == NULL)
  60                 *ec = e;
  61         else
  62         {
  63                 struct ss_eff * t;
  64
  65                 /* loop to add e to the end */
  66                 for(t = *ec;t->next != NULL;t = t->next);
  67
  68                 t->next = e;
  69         }
  70
  71         /* add buffer */
  72         if(size > 0)
  73         {
  74                 e->wave = ss_alloc_wave((int) size, 1, ss_frequency, -1);
  75                 ss_prepare_wave(e->wave);
  76         }
  77
  78         e->gain = gain;
  79         e->func = func;
  80
  81         return(e);
  82 }
  83
  84
  85 static void ss_eff_set_lfo(struct ss_eff * e, double freq,
  86         double phase, double depth)
  87 /* sets an alfo */
  88 {
  89         e->lfo = phase * 6.28;
  90         e->lfo_inc = (freq * 6.28) / (double) ss_frequency;
  91         e->lfo_depth = MS2F(depth);
  92 }
  93
  94
  95 static double ss_eff_lfo(struct ss_eff * e)
  96 /* processes an lfo */
  97 {
  98         double r = sin(e->lfo);
  99         e->lfo += e->lfo_inc;
 100
 101         return(r);
 102 }
 103
 104
 105 /**
 106  * ss_eff_process - Processes a chain of digital effects
 107  * @e: the effect chain
 108  * @s: input sample
 109  *
 110  * Processes a chain of digital effects, taking each one as input
 111  * the output of the previous one.
 112  */
 113 sample_t ss_eff_process(struct ss_eff * e, sample_t s)
 114 {
 115         while(e != NULL)
 116         {
 117                 /* filter */
 118                 s = e->func(e, s);
 119
 120                 /* increment cursor */
 121                 if(e->wave != NULL)
 122                 {
 123                         if(++e->cursor >= e->wave->size)
 124                                 e->cursor = 0;
 125                 }
 126
 127                 /* move to next */
 128                 e = e->next;
 129         }
 130
 131         return(s);
 132 }
 133
 134
 135 /**
 136  * ss_eff_off - Destroys a chain of digital effects
 137  * @ec: the effect chain
 138  *
 139  * Destroys a chain of digital effects.
 140  */
 141 void ss_eff_off(struct ss_eff ** ec)
 142 {
 143         while(*ec != NULL)
 144         {
 145                 struct ss_eff * e = (*ec)->next;
 146
 147                 /* free the buffer, if any */
 148                 if((*ec)->wave != NULL)
 149                         ss_free_wave((*ec)->wave);
 150
 151                 /* free the effect itself */
 152                 free(*ec);
 153
 154                 /* move to next */
 155                 *ec = e;
 156         }
 157 }
 158
 159
 160 /* effects */
 161
 162 static sample_t * eff_cursor_ptr(struct ss_eff * e)
 163 /* returns a pointer to the current sample */
 164 {
 165         sample_t * wave = e->wave->wave[0];
 166         return(wave + (int) e->cursor);
 167 }
 168
 169
 170 /* delay */
 171
 172 static sample_t func_delay(struct ss_eff * e, sample_t input)
 173 {
 174         sample_t * p;
 175         sample_t s;
 176
 177         p = eff_cursor_ptr(e);
 178         s = *p;
 179         *p = input;
 180
 181         return(s);
 182 }
 183
 184
 185 /**
 186  * ss_eff_delay - Adds a delay effect.
 187  * @ec: the effect chain
 188  * @size: delay in milliseconds
 189  *
 190  * Adds a delay effect. On output, this effect will simply
 191  * delay the output of the samples fed to it in @size
 192  * frames. No further filtering is done.
 193  */
 194 void ss_eff_delay(struct ss_eff ** ec, double size)
 195 {
 196         ss_eff_add(ec, size, 0, func_delay);
 197 }
 198
 199
 200 /* echo */
 201
 202 static sample_t func_echo(struct ss_eff * e, sample_t input)
 203 {
 204         sample_t * p;
 205         sample_t s;
 206
 207         p = eff_cursor_ptr(e);
 208         s = *p * e->gain;
 209         *p = input;
 210
 211         return(input + s);
 212 }
 213
 214
 215 /**
 216  * ss_eff_echo - Adds an echo effect.
 217  * @ec: the effect chain
 218  * @size: delay in milliseconds
 219  * @gain: echo gain
 220  *
 221  * Adds an echo effect. Outputs the current sample mixed
 222  * with the product of the sample sent @size frames ago
 223  * multiplied by the specified @gain.
 224  */
 225 void ss_eff_echo(struct ss_eff ** ec, double size, sample_t gain)
 226 {
 227         ss_eff_add(ec, size, gain, func_echo);
 228 }
 229
 230
 231 /* comb */
 232
 233 static sample_t func_comb(struct ss_eff * e, sample_t input)
 234 {
 235         sample_t * p;
 236         sample_t s;
 237
 238         p = eff_cursor_ptr(e);
 239         s = *p;
 240         *p = input + (s * e->gain);
 241
 242         return(input + s);
 243 }
 244
 245
 246 /**
 247  * ss_effect_comb - Adds a comb filter.
 248  * @ec: the effect chain
 249  * @size: delay in milliseconds
 250  * @gain: filter gain
 251  *
 252  * Adds a comb filter, being @size the number of samples to
 253  * delay and @gain the feedback output. Comb filters are
 254  * used in reverbs.
 255  */
 256 void ss_eff_comb(struct ss_eff ** ec, double size, sample_t gain)
 257 {
 258         ss_eff_add(ec, size, gain, func_comb);
 259 }
 260
 261
 262 /* allpass */
 263
 264 static sample_t func_allpass(struct ss_eff * e, sample_t input)
 265 {
 266         sample_t * p;
 267         sample_t s, t, u;
 268
 269         p = eff_cursor_ptr(e);
 270         t = *p;
 271
 272         u = input + (t * e->gain);
 273         s = t - (e->gain * u);
 274
 275         *p = u;
 276
 277         return(s);
 278 }
 279
 280
 281 /**
 282  * ss_eff_allpass - Adds an allpass filter.
 283  * @ec: the effect chain
 284  * @size: delay in milliseconds
 285  * @gain: filter gain
 286  *
 287  * Adds an allpass filter, being @size the number of samples to
 288  * delay and @gain the feedback output. Allpass filters are
 289  * used in reverbs.
 290  */
 291 void ss_eff_allpass(struct ss_eff ** ec, double size, sample_t gain)
 292 {
 293         ss_eff_add(ec, size, gain, func_allpass);
 294 }
 295
 296
 297 /* flanger */
 298
 299 static sample_t func_flanger(struct ss_eff * e, sample_t input)
 300 {
 301         double c;
 302         sample_t s;
 303         sample_t * p;
 304
 305         c = e->cursor - e->lfo_depth - (e->lfo_depth * ss_eff_lfo(e));
 306
 307         s = ss_get_sample(e->wave, 0, c) * e->gain;
 308
 309         p = eff_cursor_ptr(e);
 310         *p = input;
 311
 312         return(input + s);
 313 }
 314
 315
 316
 317 /**
 318  * ss_eff_flanger - Adds a flanger effect.
 319  * @ec: the effect chain
 320  * @size: delay in milliseconds
 321  * @gain: output gain
 322  * @depth: flanger depth in milliseconds
 323  * @freq: LFO frequency [0..1]
 324  * @phase: initial phase [0..1]
 325  *
 326  * Adds a flanger effect, being @size the number of samples
 327  * to delay, @gain the output gain, @depth the number of samples
 328  * the output will be 'flanged' (bigger values mean bigger
 329  * fluctuations in the final frequency), @freq the frequency of
 330  * the LFO in Hz and @phase the initial LFO value as a
 331  * fractional part of a period, being 0 the start of the period,
 332  * 0.5 half a period and so on. The LFO is sinusoidal.
 333  */
 334 void ss_eff_flanger(struct ss_eff ** ec, double size, sample_t gain,
 335         double depth, double freq, double phase)
 336 {
 337         struct ss_eff * e;
 338
 339         e = ss_eff_add(ec, size, gain, func_flanger);
 340         ss_eff_set_lfo(e, freq, phase, depth);
 341 }
 342
 343
 344 /* wobble */
 345
 346 static sample_t func_wobble(struct ss_eff * e, sample_t input)
 347 {
 348         sample_t s;
 349
 350         s = (input * fabs(ss_eff_lfo(e)) * e->gain) +
 351             (input * (1.0 - e->gain));
 352
 353         return(s);
 354 }
 355
 356
 357 /**
 358  * ss_effect_wobble - Adds a wobble effect.
 359  * @ec: the effect chain
 360  * @freq: frequency [0..1]
 361  * @phase: initial phase [0..1]
 362  * @gain: ammount of effect [0..1]
 363  *
 364  * Adds a wobble effect, where the sample amplitudes are
 365  * multiplied by an LFO, so sound volume wobbles from full
 366  * volume to silence twice a period. @freq is the LFO frequency
 367  * in Hz and @phase the initial LFO value as a
 368  * fractional part of a period, being 0 the start of the period,
 369  * 0.5 half a period and so on. The LFO is sinusoidal.
 370  */
 371 void ss_eff_wobble(struct ss_eff ** ec, double freq, double phase, sample_t gain)
 372 {
 373         struct ss_eff * e;
 374
 375         e = ss_eff_add(ec, 0, gain, func_wobble);
 376         ss_eff_set_lfo(e, freq, phase, 0);
 377 }
 378
 379
 380 /* square wave wobble */
 381
 382 static sample_t func_square_wobble(struct ss_eff * e, sample_t input)
 383 {
 384         return(ss_eff_lfo(e) > 0 ? input : 0);
 385 }
 386
 387
 388 /**
 389  * ss_eff_square_wobble - Adds a square wave wobble effect.
 390  * @ec: the effect chain
 391  * @freq: frequency [0..1]
 392  * @phase: initial phase [0..1]
 393  *
 394  * Adds an effect like the wobble one (see documentation for
 395  * effect_wobble()), but using a square wave, meaning that input
 396  * goes unfiltered (full amplitude) for half the period and
 397  * complete silence the other half.
 398  */
 399 void ss_eff_square_wobble(struct ss_eff ** ec, double freq, double phase)
 400 {
 401         struct ss_eff * e;
 402
 403         e = ss_eff_add(ec, 0, 0, func_square_wobble);
 404         ss_eff_set_lfo(e, freq, phase, 0);
 405 }
 406
 407
 408 /* half wobble */
 409
 410 static sample_t func_half_wobble(struct ss_eff * e, sample_t input)
 411 {
 412         sample_t s;
 413
 414         s = ss_eff_lfo(e);
 415
 416         return(s > 0.0 ? s * input : 0.0);
 417 }
 418
 419
 420 /**
 421  * ss_eff_half_wobble - Adds a half wave wobble effect.
 422  * @ec: the effect chain
 423  * @freq: frequency [0..1]
 424  * @phase: initial phase [0..1]
 425  *
 426  * Adds an effect like the wobble one (see documentation for
 427  * effect_wobble()), but returning only the first half of the
 428  * full period as a wobble and the second as silence.
 429  */
 430 void ss_eff_half_wobble(struct ss_eff ** ec, double freq, double phase)
 431 {
 432         struct ss_eff * e;
 433
 434         e = ss_eff_add(ec, 0, 0, func_half_wobble);
 435         ss_eff_set_lfo(e, freq, phase, 0);
 436 }
 437
 438
 439 /* fader */
 440
 441 static sample_t func_fader(struct ss_eff * e, sample_t input)
 442 {
 443         sample_t s;
 444
 445         s = input * e->gain;
 446         e->gain += e->igain;
 447
 448         if(e->cursor == e->wave->size - 1)
 449                 e->igain = 0;
 450
 451         return(s);
 452 }
 453
 454
 455 /**
 456  * ss_eff_fader - Adds a fader effect.
 457  * @ec: the effect chain
 458  * @size: number of milliseconds the fader will last
 459  * @initial: initial volume
 460  * @final: final volume
 461  *
 462  * Adds a fader effect. The effect will fade in or out the input
 463  * volume from @initial to @final during @size samples.
 464  */
 465 void ss_eff_fader(struct ss_eff ** ec, double size, sample_t initial, sample_t final)
 466 {
 467         struct ss_eff * e;
 468
 469         e = ss_eff_add(ec, size, initial, func_fader);
 470
 471         e->igain = (final - initial) / (sample_t) MS2F(size);
 472 }
 473
 474
 475 /**
 476  * ss_eff_reverb - Adds a simple reverb effect.
 477  * @ec: the effect chain
 478  *
 479  * Adds a simple reverb effect, using a chain of allpass filters.
 480  */
 481 void ss_eff_reverb(struct ss_eff ** ec)
 482 {
 483         ss_eff_allpass(ec, 20.0, 0.9);
 484         ss_eff_allpass(ec, 36.0, 0.9);
 485         ss_eff_allpass(ec, 39.0, 0.9);
 486 }
 487
 488
 489 /* foldback distortion */
 490
 491 static sample_t func_foldback(struct ss_eff * e, sample_t input)
 492 {
 493         sample_t s = input;
 494
 495         /* http://www.musicdsp.org/archive.php?classid=4#203 */
 496         if(input > e->gain)
 497                 s = e->gain - (input - e->gain);
 498         else
 499         if(input < -e->gain)
 500                 s = -e->gain + (-e->gain - input);
 501
 502         /* atan */
 503         /* http://www.musicdsp.org/showArchiveComment.php?ArchiveID=104 */
 504         /*s = atan(input * e->gain) / e->gain;*/
 505
 506         /* overdrive */
 507         /* http://www.musicdsp.org/archive.php?classid=4#41 */
 508         /*s = s * (fabs(s) + e->gain) / (s * s + (e->gain - 1) * fabs(s) + 1);*/
 509
 510         /* distort */
 511         /* http://www.musicdsp.org/showArchiveComment.php?ArchiveID=86 */
 512         /*s = s - e->gain * s * s * s;*/
 513
 514         return(s);
 515 }
 516
 517
 518 /**
 519  * ss_eff_foldback - Adds a foldback distortion effect.
 520  * @ec: the effect chain
 521  * @threshold: threshold to apply the folding
 522  *
 523  * Adds a foldback distortion effect. All aplitudes above the
 524  * threshold are folded back.
 525  */
 526 void ss_eff_foldback(struct ss_eff ** ec, sample_t threshold)
 527 {
 528         ss_eff_add(ec, 0, threshold, func_foldback);
 529 }