--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ext/openal-soft/Alc/bs2b.c	Sun Jun 29 18:44:17 2008 +0000
@@ -0,0 +1,203 @@
+/*-
+ * Copyright (c) 2005 Boris Mikhaylov
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <math.h>
+
+#include "bs2b.h"
+
+#ifndef M_PI
+#define M_PI  3.14159265358979323846
+#endif
+
+/* Single pole IIR filter.
+ * O[n] = a0*I[n] + a1*I[n-1] + b1*O[n-1]
+ */
+
+/* Lowpass filter */
+#define lo_filter(in, out_1) (bs2b->a0_lo*(in) + bs2b->b1_lo*(out_1))
+
+/* Highboost filter */
+#define hi_filter(in, in_1, out_1) (bs2b->a0_hi*(in) + bs2b->a1_hi*(in_1) + bs2b->b1_hi*(out_1))
+
+/* Set up all data. */
+static void init(struct bs2b *bs2b)
+{
+    double Fc_lo, Fc_hi;
+    double G_lo,  G_hi;
+    double x;
+
+    if ((bs2b->srate > 192000) || (bs2b->srate < 2000))
+        bs2b->srate = BS2B_DEFAULT_SRATE;
+
+    switch(bs2b->level)
+    {
+    case BS2B_LOW_CLEVEL: /* Low crossfeed level */
+        Fc_lo = 360.0;
+        Fc_hi = 501.0;
+        G_lo  = 0.398107170553497;
+        G_hi  = 0.205671765275719;
+        break;
+
+    case BS2B_MIDDLE_CLEVEL: /* Middle crossfeed level */
+        Fc_lo = 500.0;
+        Fc_hi = 711.0;
+        G_lo  = 0.459726988530872;
+        G_hi  = 0.228208484414988;
+        break;
+
+    case BS2B_HIGH_CLEVEL: /* High crossfeed level (virtual speakers are closer to itself) */
+        Fc_lo = 700.0;
+        Fc_hi = 1021.0;
+        G_lo  = 0.530884444230988;
+        G_hi  = 0.250105790667544;
+        break;
+
+    case BS2B_LOW_ECLEVEL: /* Low easy crossfeed level */
+        Fc_lo = 360.0;
+        Fc_hi = 494.0;
+        G_lo  = 0.316227766016838;
+        G_hi  = 0.168236228897329;
+        break;
+
+    case BS2B_MIDDLE_ECLEVEL: /* Middle easy crossfeed level */
+        Fc_lo = 500.0;
+        Fc_hi = 689.0;
+        G_lo  = 0.354813389233575;
+        G_hi  = 0.187169483835901;
+        break;
+
+    default: /* High easy crossfeed level */
+        bs2b->level = BS2B_HIGH_ECLEVEL;
+
+        Fc_lo = 700.0;
+        Fc_hi = 975.0;
+        G_lo  = 0.398107170553497;
+        G_hi  = 0.205671765275719;
+        break;
+    } /* switch */
+
+    /* $fc = $Fc / $s;
+     * $d  = 1 / 2 / pi / $fc;
+     * $x  = exp(-1 / $d);
+     */
+
+    x           = exp(-2.0 * M_PI * Fc_lo / bs2b->srate);
+    bs2b->b1_lo = x;
+    bs2b->a0_lo = G_lo * (1.0 - x);
+
+    x           = exp(-2.0 * M_PI * Fc_hi / bs2b->srate);
+    bs2b->b1_hi = x;
+    bs2b->a0_hi = 1.0 - G_hi * (1.0 - x);
+    bs2b->a1_hi = -x;
+
+    bs2b->gain  = 1.0 / (1.0 - G_hi + G_lo);
+
+    bs2b_clear(bs2b);
+} /* init */
+
+/* Exported functions.
+ * See descriptions in "bs2b.h"
+ */
+
+void bs2b_set_level(struct bs2b *bs2b, int level)
+{
+    if(level == bs2b->level)
+        return;
+    bs2b->level = level;
+    init(bs2b);
+} /* bs2b_set_level */
+
+int bs2b_get_level(struct bs2b *bs2b)
+{
+    return bs2b->level;
+} /* bs2b_get_level */
+
+void bs2b_set_srate(struct bs2b *bs2b, int srate)
+{
+    if (srate == bs2b->srate)
+        return;
+    bs2b->srate = srate;
+    init(bs2b);
+} /* bs2b_set_srate */
+
+int bs2b_get_srate(struct bs2b *bs2b)
+{
+    return bs2b->srate;
+} /* bs2b_get_srate */
+
+void bs2b_clear(struct bs2b *bs2b)
+{
+    int loopv = sizeof(bs2b->last_sample);
+
+    while (loopv)
+    {
+        ((char *)&bs2b->last_sample)[--loopv] = 0;
+    }
+} /* bs2b_clear */
+
+int bs2b_is_clear(struct bs2b *bs2b)
+{
+    int loopv = sizeof(bs2b->last_sample);
+
+    while (loopv)
+    {
+        if (((char *)&bs2b->last_sample)[--loopv] != 0)
+            return 0;
+    }
+    return 1;
+} /* bs2b_is_clear */
+
+void bs2b_cross_feed(struct bs2b *bs2b, float *sample)
+{
+    /* Lowpass filter */
+    bs2b->last_sample.lo[0] = lo_filter(sample[0], bs2b->last_sample.lo[0]);
+    bs2b->last_sample.lo[1] = lo_filter(sample[1], bs2b->last_sample.lo[1]);
+
+    /* Highboost filter */
+    bs2b->last_sample.hi[0] = hi_filter(sample[0], bs2b->last_sample.asis[0], bs2b->last_sample.hi[0]);
+    bs2b->last_sample.hi[1] = hi_filter(sample[1], bs2b->last_sample.asis[1], bs2b->last_sample.hi[1]);
+    bs2b->last_sample.asis[0] = sample[0];
+    bs2b->last_sample.asis[1] = sample[1];
+
+    /* Crossfeed */
+    sample[0] = bs2b->last_sample.hi[0] + bs2b->last_sample.lo[1];
+    sample[1] = bs2b->last_sample.hi[1] + bs2b->last_sample.lo[0];
+
+    /* Bass boost cause allpass attenuation */
+    sample[0] *= bs2b->gain;
+    sample[1] *= bs2b->gain;
+
+    /* Clipping of overloaded samples */
+#if 0
+    if (sample[0] > 1.0)
+        sample[0] = 1.0;
+    if (sample[0] < -1.0)
+        sample[0] = -1.0;
+    if (sample[1] > 1.0)
+        sample[1] = 1.0;
+    if (sample[1] < -1.0)
+        sample[1] = -1.0;
+#endif
+} /* bs2b_cross_feed */