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 <math.h>
  25
  26 #include "bs2b.h"
  27
  28 #ifndef M_PI
  29 #define M_PI  3.14159265358979323846
  30 #endif
  31
  32 /* Single pole IIR filter.
  33  * O[n] = a0*I[n] + a1*I[n-1] + b1*O[n-1]
  34  */
  35
  36 /* Lowpass filter */
  37 #define lo_filter(in, out_1) (bs2b->a0_lo*(in) + bs2b->b1_lo*(out_1))
  38
  39 /* Highboost filter */
  40 #define hi_filter(in, in_1, out_1) (bs2b->a0_hi*(in) + bs2b->a1_hi*(in_1) + bs2b->b1_hi*(out_1))
  41
  42 /* Set up all data. */
  43 static void init(struct bs2b *bs2b)
  44 {
  45     double Fc_lo, Fc_hi;
  46     double G_lo,  G_hi;
  47     double x;
  48
  49     if ((bs2b->srate > 192000) || (bs2b->srate < 2000))
  50         bs2b->srate = BS2B_DEFAULT_SRATE;
  51
  52     switch(bs2b->level)
  53     {
  54     case BS2B_LOW_CLEVEL: /* Low crossfeed level */
  55         Fc_lo = 360.0;
  56         Fc_hi = 501.0;
  57         G_lo  = 0.398107170553497;
  58         G_hi  = 0.205671765275719;
  59         break;
  60
  61     case BS2B_MIDDLE_CLEVEL: /* Middle crossfeed level */
  62         Fc_lo = 500.0;
  63         Fc_hi = 711.0;
  64         G_lo  = 0.459726988530872;
  65         G_hi  = 0.228208484414988;
  66         break;
  67
  68     case BS2B_HIGH_CLEVEL: /* High crossfeed level (virtual speakers are closer to itself) */
  69         Fc_lo = 700.0;
  70         Fc_hi = 1021.0;
  71         G_lo  = 0.530884444230988;
  72         G_hi  = 0.250105790667544;
  73         break;
  74
  75     case BS2B_LOW_ECLEVEL: /* Low easy crossfeed level */
  76         Fc_lo = 360.0;
  77         Fc_hi = 494.0;
  78         G_lo  = 0.316227766016838;
  79         G_hi  = 0.168236228897329;
  80         break;
  81
  82     case BS2B_MIDDLE_ECLEVEL: /* Middle easy crossfeed level */
  83         Fc_lo = 500.0;
  84         Fc_hi = 689.0;
  85         G_lo  = 0.354813389233575;
  86         G_hi  = 0.187169483835901;
  87         break;
  88
  89     default: /* High easy crossfeed level */
  90         bs2b->level = BS2B_HIGH_ECLEVEL;
  91
  92         Fc_lo = 700.0;
  93         Fc_hi = 975.0;
  94         G_lo  = 0.398107170553497;
  95         G_hi  = 0.205671765275719;
  96         break;
  97     } /* switch */
  98
  99     /* $fc = $Fc / $s;
 100      * $d  = 1 / 2 / pi / $fc;
 101      * $x  = exp(-1 / $d);
 102      */
 103
 104     x           = exp(-2.0 * M_PI * Fc_lo / bs2b->srate);
 105     bs2b->b1_lo = x;
 106     bs2b->a0_lo = G_lo * (1.0 - x);
 107
 108     x           = exp(-2.0 * M_PI * Fc_hi / bs2b->srate);
 109     bs2b->b1_hi = x;
 110     bs2b->a0_hi = 1.0 - G_hi * (1.0 - x);
 111     bs2b->a1_hi = -x;
 112
 113     bs2b->gain  = 1.0 / (1.0 - G_hi + G_lo);
 114
 115     bs2b_clear(bs2b);
 116 } /* init */
 117
 118 /* Exported functions.
 119  * See descriptions in "bs2b.h"
 120  */
 121
 122 void bs2b_set_level(struct bs2b *bs2b, int level)
 123 {
 124     if(level == bs2b->level)
 125         return;
 126     bs2b->level = level;
 127     init(bs2b);
 128 } /* bs2b_set_level */
 129
 130 int bs2b_get_level(struct bs2b *bs2b)
 131 {
 132     return bs2b->level;
 133 } /* bs2b_get_level */
 134
 135 void bs2b_set_srate(struct bs2b *bs2b, int srate)
 136 {
 137     if (srate == bs2b->srate)
 138         return;
 139     bs2b->srate = srate;
 140     init(bs2b);
 141 } /* bs2b_set_srate */
 142
 143 int bs2b_get_srate(struct bs2b *bs2b)
 144 {
 145     return bs2b->srate;
 146 } /* bs2b_get_srate */
 147
 148 void bs2b_clear(struct bs2b *bs2b)
 149 {
 150     int loopv = sizeof(bs2b->last_sample);
 151
 152     while (loopv)
 153     {
 154         ((char *)&bs2b->last_sample)[--loopv] = 0;
 155     }
 156 } /* bs2b_clear */
 157
 158 int bs2b_is_clear(struct bs2b *bs2b)
 159 {
 160     int loopv = sizeof(bs2b->last_sample);
 161
 162     while (loopv)
 163     {
 164         if (((char *)&bs2b->last_sample)[--loopv] != 0)
 165             return 0;
 166     }
 167     return 1;
 168 } /* bs2b_is_clear */
 169
 170 void bs2b_cross_feed(struct bs2b *bs2b, float *sample)
 171 {
 172     /* Lowpass filter */
 173     bs2b->last_sample.lo[0] = lo_filter(sample[0], bs2b->last_sample.lo[0]);
 174     bs2b->last_sample.lo[1] = lo_filter(sample[1], bs2b->last_sample.lo[1]);
 175
 176     /* Highboost filter */
 177     bs2b->last_sample.hi[0] = hi_filter(sample[0], bs2b->last_sample.asis[0], bs2b->last_sample.hi[0]);
 178     bs2b->last_sample.hi[1] = hi_filter(sample[1], bs2b->last_sample.asis[1], bs2b->last_sample.hi[1]);
 179     bs2b->last_sample.asis[0] = sample[0];
 180     bs2b->last_sample.asis[1] = sample[1];
 181
 182     /* Crossfeed */
 183     sample[0] = bs2b->last_sample.hi[0] + bs2b->last_sample.lo[1];
 184     sample[1] = bs2b->last_sample.hi[1] + bs2b->last_sample.lo[0];
 185
 186     /* Bass boost cause allpass attenuation */
 187     sample[0] *= bs2b->gain;
 188     sample[1] *= bs2b->gain;
 189
 190     /* Clipping of overloaded samples */
 191 #if 0
 192     if (sample[0] > 1.0)
 193         sample[0] = 1.0;
 194     if (sample[0] < -1.0)
 195         sample[0] = -1.0;
 196     if (sample[1] > 1.0)
 197         sample[1] = 1.0;
 198     if (sample[1] < -1.0)
 199         sample[1] = -1.0;
 200 #endif
 201 } /* bs2b_cross_feed */