ss_core.c

   1 /*
   2
   3     Ann Hell Ex Machina - Music Software
   4     Copyright (C) 2003/2005 Angel Ortega <angel@triptico.com>
   5
   6     ss_core.c - Softsynth core functions
   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 <stdlib.h>
  30 #include <string.h>
  31 #include <math.h>
  32
  33 #include "annhell.h"
  34
  35 /*******************
  36         Data
  37 ********************/
  38
  39 /* main output frequency */
  40 int ss_frequency=44100;
  41
  42 /* interpolation type: 0, none; 1, linear; 2, cubic spline; 3, lagrange */
  43 int ss_interpolation=3;
  44
  45 /* output channels */
  46 int ss_nchannels=2;
  47
  48 /* note frequencies */
  49 double ss_middle_A_freq=440.0;
  50 static double note_frequency[128];
  51
  52 /* debug level */
  53 int ss_debug=1;
  54
  55 /*******************
  56         Code
  57 ********************/
  58
  59 /**
  60  * ss_note_frequency - MIDI note to frequency converter
  61  * @note: the MIDI note
  62  *
  63  * Accepts a MIDI note number (range 0 to 127) and
  64  * returns its frequency in Hz.
  65  */
  66 double ss_note_frequency(int note)
  67 {
  68         int n;
  69
  70         if(note < 0 || note > 127)
  71                 return(0);
  72
  73         /* builds the table if empty */
  74         if(note_frequency[0] == 0.0)
  75         {
  76                 for(n=0;n < 128;n++)
  77                         note_frequency[n]=(ss_middle_A_freq / 32.0) *
  78                         pow(2.0, (((double)n - 9.0) / 12.0));
  79         }
  80
  81         return(note_frequency[note]);
  82 }
  83
  84
  85 struct ss_wave * ss_alloc_wave(int size, int n_channels, int s_rate)
  86 {
  87         struct ss_wave * w;
  88
  89         if((w=(struct ss_wave *)malloc(sizeof(struct ss_wave))) != NULL)
  90         {
  91                 int n;
  92
  93                 memset(w, '\0', sizeof(struct ss_wave));
  94
  95                 w->size=(double) size;
  96                 w->n_channels=n_channels;
  97                 w->s_rate=s_rate;
  98
  99                 /* alloc space for the pointers to the waves */
 100                 w->wave=(float **)malloc(n_channels * sizeof(float *));
 101
 102                 /* alloc space for the waves themselves */
 103                 for(n=0;n < n_channels;n++)
 104                         w->wave[n]=(float *)malloc(size * sizeof(float));
 105         }
 106
 107         return(w);
 108 }
 109
 110
 111 /**
 112  * ss_get_sample - Reads a sample from a wave buffer.
 113  * @wave: the wave PCM data
 114  * @size: size of the wave in samples
 115  * @offset: sample number to be returned
 116  *
 117  * Returns the sample number @offset from the @wave buffer
 118  * of @size size, doing interpolation if @offset
 119  * is not an integer.
 120  */
 121 float ss_get_sample(float * wave, double size, double offset)
 122 {
 123         float d, s1, s2, r=0.0;
 124         int o;
 125
 126         /* take care of wrappings */
 127         if(offset < 0) offset += size;
 128
 129         o=(int) offset;
 130
 131         switch(ss_interpolation)
 132         {
 133         case 0:
 134                 /* no interpolation */
 135                 r=wave[o];
 136                 break;
 137
 138         case 1:
 139                 /* linear interpolation */
 140                 if(offset > size - 2)
 141                         r=wave[o];
 142                 else
 143                 {
 144                         d=(float)(offset - floor(offset));
 145                         s1=wave[o];
 146                         s2=(wave[o + 1] - s1) * d;
 147
 148                         r=s1 + s2;
 149                 }
 150
 151                 break;
 152
 153         case 2:
 154                 /* cubic spline (borrowed from timidity) */
 155                 if(offset < 1 || offset > size - 3)
 156                         r=wave[o];
 157                 else
 158                 {
 159                         float s0, s3, t;
 160
 161                         s0=wave[o - 1];
 162                         s1=wave[o];
 163                         s2=wave[o + 1];
 164                         s3=wave[o + 2];
 165
 166                         t=s2;
 167
 168                         d=(float)(offset - floor(offset));
 169
 170                         s2=(6.0 * s2 +
 171                                 ((5.0 * s3 - 11.0 * s2 + 7.0 * s1 - s0) / 4.0) *
 172                                         (d + 1.0) * (d - 1.0)) * d;
 173
 174                         s1=((6.0 * s1 +
 175                                 ((5.0 * s0 - 11.0 * s1 + 7.0 * t - s3) / 4.0) *
 176                                         d * (d - 2.0)) * (1.0 - d) + s2) / 6.0;
 177
 178                         r=s1;
 179                 }
 180
 181                 break;
 182
 183         case 3:
 184                 /* lagrange (borrowed from timidity) */
 185                 if(offset < 1 || offset > size - 3)
 186                         r=wave[o];
 187                 else
 188                 {
 189                         float s0, s3;
 190
 191                         s0=wave[o - 1];
 192                         s1=wave[o];
 193                         s2=wave[o + 1];
 194                         s3=wave[o + 2];
 195
 196                         d=(float)(offset - floor(offset));
 197
 198                         s3 += -3.0 * s2 + 3.0 * s1 - s0;
 199                         s3 *= (d - 2.0) / 6.0;
 200                         s3 += s2 - 2.0 * s1 + s0;
 201                         s3 *= (d - 1.0) / 2.0;
 202                         s3 += s1 - s0;
 203                         s3 *= d;
 204                         s3 += s0;
 205
 206                         r=s3;
 207                 }
 208
 209                 break;
 210         }
 211
 212         return(r);
 213 }
 214
 215
 216 /**
 217  * ss_tempo_from_wave - Calculates a tempo from a wave
 218  * @w: the wave
 219  * @note: note to calculate the tempo from
 220  * @len: whole notes the tempo should match
 221  *
 222  * Calculates the optimal tempo for the @w wave, playing the @note,
 223  * to last @len whole notes.
 224  */
 225 double ss_tempo_from_wave(struct ss_wave * w, int note, double len)
 226 {
 227         double d;
 228
 229         d=ss_note_frequency(note) / w->base_freq;
 230
 231         /* get the length of a whole, in seconds */
 232         d *= w->s_rate / w->size;
 233
 234         /* convert to minutes */
 235         d *= 60.0;
 236
 237         /* then to bpm,s */
 238         d *= 4.0;
 239         d *= len;
 240
 241         return(d);
 242 }
 243
 244
 245 /**
 246  * ss_pitch_from_tempo - Calculates a pitch from a tempo
 247  * @w: the wave
 248  * @tempo: current tempo
 249  * @len: desired length in whole notes
 250  *
 251  * Calculates the optimal frequency (pitch) for the @w wave, at @tempo,
 252  * to last @len whole notes.
 253  */
 254 double ss_pitch_from_tempo(struct ss_wave * w, double tempo, double len)
 255 {
 256         double d;
 257
 258         /* calculate number of seconds the wave lasts */
 259         d=w->size / (double) w->s_rate;
 260
 261         /* convert to minutes, then to wpms */
 262         d /= 60.0;
 263         d *= (tempo / 4.0);
 264
 265         return(w->base_freq * d * len);
 266 }