Alc/bs2b.c

   1 /*-
   2  * Copyright (c) 2005 Boris Mikhaylov
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  18  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  19  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  20  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  21  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 #include "config.h"
  25
  26 #include <math.h>
  27 #include <string.h>
  28
  29 #include "bs2b.h"
  30
  31 #ifndef M_PI
  32 #define M_PI  3.14159265358979323846
  33 #endif
  34
  35 /* Single pole IIR filter.
  36  * O[n] = a0*I[n] + a1*I[n-1] + b1*O[n-1]
  37  */
  38
  39 /* Lowpass filter */
  40 #define lo_filter(in, out_1) (bs2b->a0_lo*(in) + bs2b->b1_lo*(out_1))
  41
  42 /* Highboost filter */
  43 #define hi_filter(in, in_1, out_1) (bs2b->a0_hi*(in) + bs2b->a1_hi*(in_1) + bs2b->b1_hi*(out_1))
  44
  45 /* Set up all data. */
  46 static void init(struct bs2b *bs2b)
  47 {
  48     double Fc_lo, Fc_hi;
  49     double G_lo,  G_hi;
  50     double x;
  51
  52     if ((bs2b->srate > 192000) || (bs2b->srate < 2000))
  53         bs2b->srate = BS2B_DEFAULT_SRATE;
  54
  55     switch(bs2b->level)
  56     {
  57     case BS2B_LOW_CLEVEL: /* Low crossfeed level */
  58         Fc_lo = 360.0;
  59         Fc_hi = 501.0;
  60         G_lo  = 0.398107170553497;
  61         G_hi  = 0.205671765275719;
  62         break;
  63
  64     case BS2B_MIDDLE_CLEVEL: /* Middle crossfeed level */
  65         Fc_lo = 500.0;
  66         Fc_hi = 711.0;
  67         G_lo  = 0.459726988530872;
  68         G_hi  = 0.228208484414988;
  69         break;
  70
  71     case BS2B_HIGH_CLEVEL: /* High crossfeed level (virtual speakers are closer to itself) */
  72         Fc_lo = 700.0;
  73         Fc_hi = 1021.0;
  74         G_lo  = 0.530884444230988;
  75         G_hi  = 0.250105790667544;
  76         break;
  77
  78     case BS2B_LOW_ECLEVEL: /* Low easy crossfeed level */
  79         Fc_lo = 360.0;
  80         Fc_hi = 494.0;
  81         G_lo  = 0.316227766016838;
  82         G_hi  = 0.168236228897329;
  83         break;
  84
  85     case BS2B_MIDDLE_ECLEVEL: /* Middle easy crossfeed level */
  86         Fc_lo = 500.0;
  87         Fc_hi = 689.0;
  88         G_lo  = 0.354813389233575;
  89         G_hi  = 0.187169483835901;
  90         break;
  91
  92     default: /* High easy crossfeed level */
  93         bs2b->level = BS2B_HIGH_ECLEVEL;
  94
  95         Fc_lo = 700.0;
  96         Fc_hi = 975.0;
  97         G_lo  = 0.398107170553497;
  98         G_hi  = 0.205671765275719;
  99         break;
 100     } /* switch */
 101
 102     /* $fc = $Fc / $s;
 103      * $d  = 1 / 2 / pi / $fc;
 104      * $x  = exp(-1 / $d);
 105      */
 106
 107     x           = exp(-2.0 * M_PI * Fc_lo / bs2b->srate);
 108     bs2b->b1_lo = x;
 109     bs2b->a0_lo = G_lo * (1.0 - x);
 110
 111     x           = exp(-2.0 * M_PI * Fc_hi / bs2b->srate);
 112     bs2b->b1_hi = x;
 113     bs2b->a0_hi = 1.0 - G_hi * (1.0 - x);
 114     bs2b->a1_hi = -x;
 115
 116     bs2b->gain  = 1.0f / (float)(1.0 - G_hi + G_lo);
 117 } /* init */
 118
 119 /* Exported functions.
 120  * See descriptions in "bs2b.h"
 121  */
 122
 123 void bs2b_set_level(struct bs2b *bs2b, int level)
 124 {
 125     if(level == bs2b->level)
 126         return;
 127     bs2b->level = level;
 128     init(bs2b);
 129 } /* bs2b_set_level */
 130
 131 int bs2b_get_level(struct bs2b *bs2b)
 132 {
 133     return bs2b->level;
 134 } /* bs2b_get_level */
 135
 136 void bs2b_set_srate(struct bs2b *bs2b, int srate)
 137 {
 138     if (srate == bs2b->srate)
 139         return;
 140     bs2b->srate = srate;
 141     init(bs2b);
 142 } /* bs2b_set_srate */
 143
 144 int bs2b_get_srate(struct bs2b *bs2b)
 145 {
 146     return bs2b->srate;
 147 } /* bs2b_get_srate */
 148
 149 void bs2b_clear(struct bs2b *bs2b)
 150 {
 151     memset(&bs2b->last_sample, 0, sizeof(bs2b->last_sample));
 152 } /* bs2b_clear */
 153
 154 void bs2b_cross_feed(struct bs2b *bs2b, float *sample)
 155 {
 156     /* Lowpass filter */
 157     bs2b->last_sample.lo[0] = lo_filter(sample[0], bs2b->last_sample.lo[0]);
 158     bs2b->last_sample.lo[1] = lo_filter(sample[1], bs2b->last_sample.lo[1]);
 159
 160     /* Highboost filter */
 161     bs2b->last_sample.hi[0] = hi_filter(sample[0], bs2b->last_sample.asis[0], bs2b->last_sample.hi[0]);
 162     bs2b->last_sample.hi[1] = hi_filter(sample[1], bs2b->last_sample.asis[1], bs2b->last_sample.hi[1]);
 163     bs2b->last_sample.asis[0] = sample[0];
 164     bs2b->last_sample.asis[1] = sample[1];
 165
 166     /* Crossfeed */
 167     sample[0] = (float)(bs2b->last_sample.hi[0] + bs2b->last_sample.lo[1]);
 168     sample[1] = (float)(bs2b->last_sample.hi[1] + bs2b->last_sample.lo[0]);
 169
 170     /* Bass boost cause allpass attenuation */
 171     sample[0] *= bs2b->gain;
 172     sample[1] *= bs2b->gain;
 173
 174     /* Clipping of overloaded samples */
 175 #if 0
 176     if (sample[0] > 1.0)
 177         sample[0] = 1.0;
 178     if (sample[0] < -1.0)
 179         sample[0] = -1.0;
 180     if (sample[1] > 1.0)
 181         sample[1] = 1.0;
 182     if (sample[1] < -1.0)
 183         sample[1] = -1.0;
 184 #endif
 185 } /* bs2b_cross_feed */