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initial forking of open-al to create multiple listeners
author Robert McIntyre <rlm@mit.edu>
date Tue, 25 Oct 2011 13:02:31 -0700
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-1:000000000000 0:f9476ff7637e
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
28 #include "bs2b.h"
29
30 #ifndef M_PI
31 #define M_PI 3.14159265358979323846
32 #endif
33
34 /* Single pole IIR filter.
35 * O[n] = a0*I[n] + a1*I[n-1] + b1*O[n-1]
36 */
37
38 /* Lowpass filter */
39 #define lo_filter(in, out_1) (bs2b->a0_lo*(in) + bs2b->b1_lo*(out_1))
40
41 /* Highboost filter */
42 #define hi_filter(in, in_1, out_1) (bs2b->a0_hi*(in) + bs2b->a1_hi*(in_1) + bs2b->b1_hi*(out_1))
43
44 /* Set up all data. */
45 static void init(struct bs2b *bs2b)
46 {
47 double Fc_lo, Fc_hi;
48 double G_lo, G_hi;
49 double x;
50
51 if ((bs2b->srate > 192000) || (bs2b->srate < 2000))
52 bs2b->srate = BS2B_DEFAULT_SRATE;
53
54 switch(bs2b->level)
55 {
56 case BS2B_LOW_CLEVEL: /* Low crossfeed level */
57 Fc_lo = 360.0;
58 Fc_hi = 501.0;
59 G_lo = 0.398107170553497;
60 G_hi = 0.205671765275719;
61 break;
62
63 case BS2B_MIDDLE_CLEVEL: /* Middle crossfeed level */
64 Fc_lo = 500.0;
65 Fc_hi = 711.0;
66 G_lo = 0.459726988530872;
67 G_hi = 0.228208484414988;
68 break;
69
70 case BS2B_HIGH_CLEVEL: /* High crossfeed level (virtual speakers are closer to itself) */
71 Fc_lo = 700.0;
72 Fc_hi = 1021.0;
73 G_lo = 0.530884444230988;
74 G_hi = 0.250105790667544;
75 break;
76
77 case BS2B_LOW_ECLEVEL: /* Low easy crossfeed level */
78 Fc_lo = 360.0;
79 Fc_hi = 494.0;
80 G_lo = 0.316227766016838;
81 G_hi = 0.168236228897329;
82 break;
83
84 case BS2B_MIDDLE_ECLEVEL: /* Middle easy crossfeed level */
85 Fc_lo = 500.0;
86 Fc_hi = 689.0;
87 G_lo = 0.354813389233575;
88 G_hi = 0.187169483835901;
89 break;
90
91 default: /* High easy crossfeed level */
92 bs2b->level = BS2B_HIGH_ECLEVEL;
93
94 Fc_lo = 700.0;
95 Fc_hi = 975.0;
96 G_lo = 0.398107170553497;
97 G_hi = 0.205671765275719;
98 break;
99 } /* switch */
100
101 /* $fc = $Fc / $s;
102 * $d = 1 / 2 / pi / $fc;
103 * $x = exp(-1 / $d);
104 */
105
106 x = exp(-2.0 * M_PI * Fc_lo / bs2b->srate);
107 bs2b->b1_lo = x;
108 bs2b->a0_lo = G_lo * (1.0 - x);
109
110 x = exp(-2.0 * M_PI * Fc_hi / bs2b->srate);
111 bs2b->b1_hi = x;
112 bs2b->a0_hi = 1.0 - G_hi * (1.0 - x);
113 bs2b->a1_hi = -x;
114
115 bs2b->gain = 1.0 / (1.0 - G_hi + G_lo);
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 */