engines/common/BiquadFilter.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the Free Software           *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#ifndef __LS_BIQUADFILTER_H__
#define __LS_BIQUADFILTER_H__

#include <math.h>

#include "../../common/global.h"

/// ln(2) / 2
#define LN_2_2                  0.34657359f

#ifndef LIMIT
# define LIMIT(v,l,u)           (v < l ? l : (v > u ? u : v))
#endif

namespace LinuxSampler {

    typedef float bq_t;

    /**
     * Internal parameters of the biquad filter, which are actually the
     * final parameters of the filter's transfer function. This strucure is
     * only needed when these parameters should stored outside the
     * BiquadFilter class, e.g. to save calculation time by sharing them
     * between multiple filters.
     */
    struct biquad_param_t {
        bq_t b0;
        bq_t b1;
        bq_t b2;
        bq_t a1;
        bq_t a2;
    };

    /**
     * Bi-quadratic filter
     * (adapted from lisp code by Eli Brandt, http://www.cs.cmu.edu/~eli/)
     */
    class BiquadFilter {
        protected:
            // following five variables are only used if no external biquad_param_t reference is used
            bq_t b0;
            bq_t b1;
            bq_t b2;
            bq_t a1;
            bq_t a2;
            // following four variables are used to buffer the feedback
            bq_t x1;
            bq_t x2;
            bq_t y1;
            bq_t y2;

            const static float fbc = 0.98;

            /**
             * Prevent \a f from going into denormal mode which would slow down
             * subsequent floating point calculations, we achieve that by setting
             * \a f to zero when it falls under the denormal threshold value.
             */
            inline void KillDenormal(bq_t& f) {
                // TODO: this is a generic solution for 32bit floats, should be replaced by CPU specific asm code
                f += 1e-18f;
                f -= 1e-18f;
            }
        public:
            BiquadFilter() {
                Reset();
            }

            void Reset() {
                x1 = 0.0f;
                x2 = 0.0f;
                y1 = 0.0f;
                y2 = 0.0f;
            }

            inline bq_t Apply(const bq_t x) {
                bq_t y;

                y = this->b0 * x + this->b1 * this->x1 + this->b2 * this->x2 +
                    this->a1 * this->y1 + this->a2 * this->y2;
                KillDenormal(y);
                this->x2 = this->x1;
                this->x1 = x;
                this->y2 = this->y1;
                this->y1 = y;

                return y;
            }

            inline bq_t Apply(biquad_param_t* param, const bq_t x) {
                bq_t y;

                y = param->b0 * x + param->b1 * this->x1 + param->b2 * this->x2 +
                    param->a1 * this->y1 + param->a2 * this->y2;
                KillDenormal(y);
                this->x2 = this->x1;
                this->x1 = x;
                this->y2 = this->y1;
                this->y1 = y;

                return y;
            }

#if ARCH_X86
            // expects to find input in xmm0 (xmm0 stays unmodified) and finally leaves output in xmm6
            inline void Apply4StepsSSE(biquad_param_t* param) {
                __asm__ __volatile__ (
                    "movss (%2),%%xmm4                # b0\n\t"
                    "shufps   $0x00,%%xmm4,%%xmm4     # copy b0 to other cells\n\t"
                    "mulps  %%xmm0,%%xmm4             # xmm4 = x*b0\n\t"
                    "movups (%0),%%xmm2               # load b1,b2,a1,a2\n\t"
                    "movups (%1),%%xmm5               # load x1,x2,y1,y2\n\t"
                    /* sample 0 */
                    "movaps %%xmm5,%%xmm3\n\t"
                    "mulps  %%xmm2,%%xmm5             # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
                    "shufps $0x0a,%%xmm3,%%xmm3       # x2 = x1, y2 = y1\n\t"
                    "movss  %%xmm4,%%xmm6\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6             # xmm6 = b0*x + b1*x1 + b2*x2 + a1*y1 + a2*y2\n\t"
                    /* sample 1 */
                    "shufps $0x39,%%xmm4,%%xmm4       # rotate xmm4 down 1 cell\n\t"
                    "movss  %%xmm6,%%xmm3             # y1 = y\n\t"
                    "shufps $0x4e,%%xmm3,%%xmm3       # rotate 2 cells\n\t"
                    "movss  %%xmm0,%%xmm3             # x1 = x\n\t"
                    "shufps $0x93,%%xmm6,%%xmm6       # rotate output up 1 cell\n\t"
                    "movaps %%xmm3,%%xmm5\n\t"
                    "shufps $0x39,%%xmm0,%%xmm0       # rotate input down 1 cell\n\t"
                    "mulps  %%xmm2,%%xmm5             # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
                    "movss  %%xmm5,%%xmm6\n\t"
                    "addss  %%xmm4,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6             # xmm6 = b0*x + b1*x1 + b2*x2 + a1*y1 + a2*y2\n\t"
                    /* sample 2 */
                    "shufps $0x0a,%%xmm3,%%xmm3       # x2 = x1, y2 = y1\n\t"
                    "shufps $0x39,%%xmm4,%%xmm4       # rotate xmm4 down 1 cell\n\t"
                    "movss  %%xmm6,%%xmm3             # y1 = y\n\t"
                    "shufps $0x4e,%%xmm3,%%xmm3       # rotate 2 cells\n\t"
                    "movss  %%xmm0,%%xmm3             # x1 = x\n\t"
                    "shufps $0x93,%%xmm6,%%xmm6       # rotate output up 1 cell\n\t"
                    "movaps %%xmm3,%%xmm5\n\t"
                    "shufps $0x39,%%xmm0,%%xmm0       # rotate input down 1 cell\n\t"
                    "mulps  %%xmm2,%%xmm5             # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
                    "movss  %%xmm5,%%xmm6\n\t"
                    "addss  %%xmm4,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6\n\t"
                    "shufps $0x39,%%xmm5,%%xmm5\n\t"
                    "addss  %%xmm5,%%xmm6             # xmm6 = b0*x + b1*x1 + b2*x2 + a1*y1 + a2*y2\n\t"
                    /* sample 3 */
                    "shufps $0x0a,%%xmm3,%%xmm3       # x2 = x1, y2 = y1\n\t"
                    "shufps $0x39,%%xmm4,%%xmm4       # rotate xmm4 down 1 cell\n\t"
                    "movss  %%xmm6,%%xmm3             # y1 = y\n\t"
                    "shufps $0x4e,%%xmm3,%%xmm3       # rotate 2 cells\n\t"
                    "movss  %%xmm0,%%xmm3             # x1 = x\n\t"
                    "shufps $0x93,%%xmm6,%%xmm6       # rotate output up 1 cell\n\t"
                    "mulps  %%xmm3,%%xmm2             # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
                    "shufps $0x39,%%xmm0,%%xmm0       # rotate input down 1 cell\n\t"
                    "movss  %%xmm2,%%xmm6\n\t"
                    "shufps $0x39,%%xmm2,%%xmm2\n\t"
                    "addss  %%xmm2,%%xmm6\n\t"
                    "shufps $0x39,%%xmm2,%%xmm2\n\t"
                    "addss  %%xmm2,%%xmm6\n\t"
                    "shufps $0x39,%%xmm2,%%xmm2\n\t"
                    "addss  %%xmm2,%%xmm6\n\t"
                    "addss  %%xmm4,%%xmm6             # xmm6 = b0*x + b1*x1 + b2*x2 + a1*y1 + a2*y2\n\t"
                    /* done */
                    "shufps $0x0a,%%xmm3,%%xmm3       # x2 = x1, y2 = y1\n\t"
                    "movss  %%xmm6,%%xmm3             # y1 = y\n\t"
                    "shufps $0x4e,%%xmm3,%%xmm3       # rotate 2 cells\n\t"
                    "movss  %%xmm0,%%xmm3             # x1 = x\n\t"
                    "shufps $0x1b,%%xmm6,%%xmm6       # swap output to correct order\n\t"
                    "shufps $0x39,%%xmm0,%%xmm0       # rotate input down 1 cell, to restore original input\n\t"
                    "movups %%xmm3,(%1)               # store x1,x2,y1,y2\n\t"
                    : /* no output */
                    : "r" (&param->b1), /* %0 - [b1,b2,a1,a2] */
                      "r" (&x1),        /* %1 - [x1,x2,y1,y2] */
                      "r" (&param->b0)  /* %2 */
                );
            }
#endif // ARCH_X86

            inline bq_t ApplyFB(bq_t x, const bq_t fb) {
                bq_t y;

                x += this->y1 * fb * 0.98;
                y = this->b0 * x + this->b1 * this->x1 + this->b2 * this->x2 +
                    this->a1 * this->y1 + this->a2 * this->y2;
                KillDenormal(y);
                this->x2 = this->x1;
                this->x1 = x;
                this->y2 = this->y1;
                this->y1 = y;

                return y;
            }

            inline bq_t ApplyFB(biquad_param_t* param, bq_t x, const bq_t fb) {
                bq_t y;

                x += this->y1 * fb * 0.98;
                y = param->b0 * x + param->b1 * this->x1 + param->b2 * this->x2 +
                    param->a1 * this->y1 + param->a2 * this->y2;
                KillDenormal(y);
                this->x2 = this->x1;
                this->x1 = x;
                this->y2 = this->y1;
                this->y1 = y;

                return y;
            }

#if ARCH_X86
            // expects to find input in xmm0 (xmm0 stays unmodified) and finally leaves output in xmm7
            inline void ApplyFB4StepsSSE(biquad_param_t* param, const bq_t &fb) {
                float xs, ys;
                float t0, t1, t2, t3, t4, t5, t6, t7, t8; // temporary stack space
                __asm__ __volatile__ (
                    /* prepare input */
                    "movss  %15,%%xmm5\n\t"
                    "movss  %%xmm0,(%14)\n\t"
                    /* sample 0 */
                    "movss   %0, %%xmm3\n\t"
                    "movss   %1, %%xmm4\n\t"
                    "mulss   %%xmm4, %%xmm5\n\t"
                    "movss   %%xmm3, %2\n\t"
                    "movss   %%xmm5, %16\n\t"
                    "mulss   %%xmm3, %%xmm5\n\t"
                    "movss   %19, %%xmm2\n\t"
                    "movss   %3, %%xmm6\n\t"
                    "movss   %21, %%xmm3\n\t"
                    "addss   %%xmm5, %%xmm6\n\t"
                    "movss  %%xmm2, %%xmm5\n\t"
                    "movss   %20, %%xmm4\n\t"
                    "movss   %%xmm6, %4\n\t"
                    "mulss   %%xmm6, %%xmm5\n\t"
                    "movss   %5, %%xmm6\n\t"
                    "movss   %%xmm2, %6\n\t"
                    "movss   %%xmm4, %7\n\t"
                    "movss   %%xmm3, %%xmm2\n\t"
                    "mulss   %%xmm6, %%xmm4\n\t"
                    "mulss   %8, %%xmm2\n\t"
                    "movss   %%xmm3, %9\n\t"
                    "addss   %%xmm4, %%xmm5\n\t"
                    "movss   %18, %%xmm3\n\t"
                    "movss   %17, %%xmm4\n\t"
                    "addss   %%xmm2, %%xmm5\n\t"
                    "movss   %%xmm4, %10\n\t"
                    "movss   %%xmm3, %%xmm2\n\t"
                    "mulss   %11, %%xmm4\n\t"
                    "mulss   %12, %%xmm2\n\t"
                    "movss   %%xmm3, %13\n\t"
                    "addss   %%xmm4, %%xmm5\n\t"
                    "movss   %11, %%xmm3\n\t"
                    "movss   %4, %%xmm4\n\t"
                    "addss   %%xmm2, %%xmm5\n\t"
                    :: "m" (y1),  /* %0 */
                       "m" (fbc), /* %1 */
                       "m" (t0),  /* %2 */
                       "m" (xs),  /* %3 */
                       "m" (t7),  /* %4 */
                       "m" (x1),  /* %5 */
                       "m" (t1),  /* %6 */
                       "m" (t2),  /* %7 */
                       "m" (x2),  /* %8 */
                       "m" (t3),  /* %9 */
                       "m" (t4),  /* %10 */
                       "m" (t0),  /* %11 */
                       "m" (y2),  /* %12 */
                       "m" (t5),  /* %13 */
                       "r" (&xs),  /* %14 */
                       "m" (fb),   /* %15 */
                       "m" (ys),   /* %16 */
                       "m" (param->a1), /* %17 */
                       "m" (param->a2), /* %18 */
                       "m" (param->b0), /* %19 */
                       "m" (param->b1), /* %20 */
                       "m" (param->b2) /* %21 */
                );
                __asm__ __volatile__ (
                    "shufps $0x39,%%xmm0,%%xmm0  # rotate down one cell\n\t"
                    "movss  %%xmm5,%%xmm7\n\t"
                    ::
                );
                /* sample 1 */
                __asm__ __volatile__ (
                    "movss   %0, %%xmm4\n\t"
                    "movss   %%xmm0, %%xmm3\n\t"
                    "mulss   %%xmm5, %%xmm4\n\t"
                    "mulss   %3, %%xmm6\n\t"
                    "movss   %5, %%xmm2\n\t"
                    "addss   %%xmm4, %%xmm3\n\t"
                    "mulss   %7, %%xmm2\n\t"
                    "movss   %6, %%xmm4\n\t"
                    "movss   %%xmm3, %8\n\t"
                    "mulss   %%xmm3, %%xmm4\n\t"
                    "addss   %%xmm2, %%xmm4\n\t"
                    "movss   %9, %%xmm3\n\t"
                    "mulss   %%xmm5, %%xmm3\n\t"
                    "movss   %10, %%xmm2\n\t"
                    "addss   %%xmm6, %%xmm4\n\t"
                    "mulss   %11, %%xmm2\n\t"
                    "addss   %%xmm3, %%xmm4\n\t"
                    "addss   %%xmm2, %%xmm4\n\t"
                    :: "m" (ys),  /* %0 */
                       "m" (fbc), /* %1 */
                       "m" (xs),  /* %2 */
                       "m" (t3),  /* %3 */
                       "m" (y2),  /* %4 */
                       "m" (t2),  /* %5 */
                       "m" (t1),  /* %6 */
                       "m" (t7),  /* %7 */
                       "m" (t8),  /* %8 */
                       "m" (t4),  /* %9 */
                       "m" (t5),  /* %10 */
                       "m" (t0),  /* %11 */
                       "m" (x2),  /* %12 */
                       "m" (x1),  /* %13 */
                       "m" (y1)   /* %14 */
                );
                __asm__ __volatile__ (
                    "shufps $0x93,%%xmm7,%%xmm7  # rotate up one cell\n\t"
                    "shufps $0x39,%%xmm0,%%xmm0  # rotate down one cell\n\t"
                    "movss  %%xmm4,%%xmm7\n\t"
                    ::
                );
                /* sample 2 */
                __asm__ __volatile__ (
                    "movss   %2, %%xmm6\n\t"
                    "movss   %3, %%xmm3\n\t"
                    "mulss   %%xmm4, %%xmm6\n\t"
                    "movss   %4, %%xmm2\n\t"
                    "mulss   %9, %%xmm2\n\t"
                    "addss   %%xmm0, %%xmm6\n\t"
                    "mulss   %7, %%xmm5\n\t"
                    "mulss   %%xmm6, %%xmm3\n\t"
                    "addss   %%xmm2, %%xmm3\n\t"
                    "movss   %5, %%xmm2\n\t"
                    "mulss   %8, %%xmm2\n\t"
                    "addss   %%xmm2, %%xmm3\n\t"
                    "movss   %6, %%xmm2\n\t"
                    "mulss   %%xmm4, %%xmm2\n\t"
                    "addss   %%xmm5, %%xmm2\n\t"
                    "addss   %%xmm2, %%xmm3\n\t"
                    :: "m" (xs),  /* %0 */
                       "m" (fb),  /* %1 */
                       "m" (ys), /* %2 */
                       "m" (t1),  /* %3 */
                       "m" (t2),  /* %4 */
                       "m" (t3),  /* %5 */
                       "m" (t4),  /* %6 */
                       "m" (t5),  /* %7 */
                       "m" (t7),  /* %8 */
                       "m" (t8),  /* %9 */
                       "m" (x1),  /* %10 */
                       "m" (x2),  /* %11 */
                       "m" (y1),  /* %12 */
                       "m" (y2)   /* %13 */
                );
                __asm__ __volatile__ (
                    "shufps $0x39,%%xmm0,%%xmm0  # rotate down one cell\n\t"
                    "shufps $0x93,%%xmm7,%%xmm7  # rotate up one cell\n\t"
                    "movss  %%xmm3,%%xmm7\n\t"
                    ::
                );
                /* sample 3 */
                __asm__ __volatile__ (
                    "movss   %1, %%xmm2\n\t"
                    "mulss   %7, %%xmm4\n\t"
                    "mulss   %%xmm3, %%xmm2\n\t"
                    "movss   %3, %%xmm5\n\t"
                    "movss   %%xmm6, %11\n\t"
                    "addss   %%xmm0, %%xmm2\n\t"
                    "movss   %%xmm3, %13\n\t"
                    "mulss   %%xmm2, %%xmm5\n\t"
                    "mulss   %4, %%xmm6\n\t"
                    "movss   %%xmm2, %10\n\t"
                    "addss   %%xmm6, %%xmm5\n\t"
                    "movss   %5, %%xmm2\n\t"
                    "mulss   %9, %%xmm2\n\t"
                    "mulss   %6, %%xmm3\n\t"
                    "addss   %%xmm2, %%xmm5\n\t"
                    "addss   %%xmm3, %%xmm4\n\t"
                    "addss   %%xmm4, %%xmm5\n\t"
                    "movss   %%xmm5, %12\n\t"
                    :: "m" (xs),  /* %0 */
                       "m" (ys),  /* %1 */
                       "m" (fbc), /* %2 */
                       "m" (t1),  /* %3 */
                       "m" (t2),  /* %4 */
                       "m" (t3),  /* %5 */
                       "m" (t4),  /* %6 */
                       "m" (t5),  /* %7 */
                       "m" (t6),  /* %8 */
                       "m" (t8),  /* %9 */
                       "m" (x1),  /* %10 */
                       "m" (x2),  /* %11 */
                       "m" (y1),  /* %12 */
                       "m" (y2)   /* %13 */
                );
                __asm__ __volatile__ (
                    "shufps $0x93,%%xmm7,%%xmm7  # rotate up one cell\n\t"
                    "shufps $0x39,%%xmm0,%%xmm0  # rotate down one cell to restore original input\n\t"
                    "movss  %%xmm5,%%xmm7\n\t"
                    "shufps $0x1b,%%xmm7,%%xmm7  # swap output to correct order\n\t"
                    ::
                );
            }
    };
#endif // ARCH_X86

    class LowpassFilter : public BiquadFilter {
        public:
            inline LowpassFilter() : BiquadFilter() {}

            inline void SetParameters(bq_t fc, bq_t bw, bq_t fs) {
                bq_t omega = 2.0 * M_PI * fc / fs;
                bq_t sn    = sin(omega);
                bq_t cs    = cos(omega);
                bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);

                const float a0r = 1.0 / (1.0 + alpha);
                this->b0 = a0r * (1.0 - cs) * 0.5;
                this->b1 = a0r * (1.0 - cs);
                this->b2 = a0r * (1.0 - cs) * 0.5;
                this->a1 = a0r * (2.0 * cs);
                this->a2 = a0r * (alpha - 1.0);
            }

            inline void SetParameters(biquad_param_t* param, bq_t fc, bq_t bw, bq_t fs) {
                bq_t omega = 2.0 * M_PI * fc / fs;
                bq_t sn    = sin(omega);
                bq_t cs    = cos(omega);
                bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);

                const float a0r = 1.0 / (1.0 + alpha);
                param->b0 = a0r * (1.0 - cs) * 0.5;
                param->b1 = a0r * (1.0 - cs);
                param->b2 = a0r * (1.0 - cs) * 0.5;
                param->a1 = a0r * (2.0 * cs);
                param->a2 = a0r * (alpha - 1.0);
            }
    };

    class BandpassFilter : public BiquadFilter {
        public:
            inline BandpassFilter() : BiquadFilter() {}

            inline void SetParameters(bq_t fc, bq_t bw, bq_t fs) {
                bq_t omega = 2.0 * M_PI * fc / fs;
                bq_t sn    = sin(omega);
                bq_t cs    = cos(omega);
                bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);

                const float a0r = 1.0 / (1.0 + alpha);
                this->b0 = a0r * alpha;
                this->b1 = 0.0;
                this->b2 = a0r * -alpha;
                this->a1 = a0r * (2.0 * cs);
                this->a2 = a0r * (alpha - 1.0);
            }

            inline void SetParameters(biquad_param_t* param, bq_t fc, bq_t bw, bq_t fs) {
                bq_t omega = 2.0 * M_PI * fc / fs;
                bq_t sn    = sin(omega);
                bq_t cs    = cos(omega);
                bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);

                const float a0r = 1.0 / (1.0 + alpha);
                param->b0 = a0r * alpha;
                param->b1 = 0.0;
                param->b2 = a0r * -alpha;
                param->a1 = a0r * (2.0 * cs);
                param->a2 = a0r * (alpha - 1.0);
            }
    };

    class HighpassFilter : public BiquadFilter {
        public:
            inline HighpassFilter() : BiquadFilter() {}

            inline void SetParameters(bq_t fc, bq_t bw, bq_t fs) {
                bq_t omega = 2.0 * M_PI * fc / fs;
                bq_t sn    = sin(omega);
                bq_t cs    = cos(omega);
                bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);

                const float a0r = 1.0 / (1.0 + alpha);
                this->b0 = a0r * (1.0 + cs) * 0.5;
                this->b1 = a0r * -(1.0 + cs);
                this->b2 = a0r * (1.0 + cs) * 0.5;
                this->a1 = a0r * (2.0 * cs);
                this->a2 = a0r * (alpha - 1.0);
            }

            inline void SetParameters(biquad_param_t* param, bq_t fc, bq_t bw, bq_t fs) {
                bq_t omega = 2.0 * M_PI * fc / fs;
                bq_t sn    = sin(omega);
                bq_t cs    = cos(omega);
                bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);

                const float a0r = 1.0 / (1.0 + alpha);
                param->b0 = a0r * (1.0 + cs) * 0.5;
                param->b1 = a0r * -(1.0 + cs);
                param->b2 = a0r * (1.0 + cs) * 0.5;
                param->a1 = a0r * (2.0 * cs);
                param->a2 = a0r * (alpha - 1.0);
            }
    };

} // namespace LinuxSampler

#endif // __LS_BIQUADFILTER_H__
1	schoenebeck	53	/***************************************************************************
2			* *
3			* LinuxSampler - modular, streaming capable sampler *
4			* *
5	schoenebeck	56	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	schoenebeck	53	* *
7			* This program is free software; you can redistribute it and/or modify *
8			* it under the terms of the GNU General Public License as published by *
9			* the Free Software Foundation; either version 2 of the License, or *
10			* (at your option) any later version. *
11			* *
12			* This program is distributed in the hope that it will be useful, *
13			* but WITHOUT ANY WARRANTY; without even the implied warranty of *
14			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
15			* GNU General Public License for more details. *
16			* *
17			* You should have received a copy of the GNU General Public License *
18			* along with this program; if not, write to the Free Software *
19			* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
20			* MA 02111-1307 USA *
21			***************************************************************************/
22
23			#ifndef __LS_BIQUADFILTER_H__
24			#define __LS_BIQUADFILTER_H__
25
26	capela	268	#include <math.h>
27
28	schoenebeck	328	#include "../../common/global.h"
29
30	schoenebeck	53	/// ln(2) / 2
31			#define LN_2_2 0.34657359f
32
33			#ifndef LIMIT
34			# define LIMIT(v,l,u) (v < l ? l : (v > u ? u : v))
35			#endif
36
37			namespace LinuxSampler {
38
39			typedef float bq_t;
40
41			/**
42	schoenebeck	80	* Internal parameters of the biquad filter, which are actually the
43			* final parameters of the filter's transfer function. This strucure is
44			* only needed when these parameters should stored outside the
45			* BiquadFilter class, e.g. to save calculation time by sharing them
46			* between multiple filters.
47			*/
48			struct biquad_param_t {
49			bq_t b0;
50			bq_t b1;
51			bq_t b2;
52	senkov	324	bq_t a1;
53			bq_t a2;
54	schoenebeck	80	};
55
56			/**
57			* Bi-quadratic filter
58			* (adapted from lisp code by Eli Brandt, http://www.cs.cmu.edu/~eli/)
59			*/
60	schoenebeck	53	class BiquadFilter {
61			protected:
62	schoenebeck	80	// following five variables are only used if no external biquad_param_t reference is used
63	schoenebeck	53	bq_t b0;
64			bq_t b1;
65			bq_t b2;
66	senkov	324	bq_t a1;
67			bq_t a2;
68	schoenebeck	80	// following four variables are used to buffer the feedback
69	schoenebeck	53	bq_t x1;
70			bq_t x2;
71			bq_t y1;
72			bq_t y2;
73
74	schoenebeck	319	const static float fbc = 0.98;
75
76	schoenebeck	53	/**
77	schoenebeck	80	* Prevent \a f from going into denormal mode which would slow down
78			* subsequent floating point calculations, we achieve that by setting
79			* \a f to zero when it falls under the denormal threshold value.
80			*/
81			inline void KillDenormal(bq_t& f) {
82	schoenebeck	53	// TODO: this is a generic solution for 32bit floats, should be replaced by CPU specific asm code
83			f += 1e-18f;
84			f -= 1e-18f;
85			}
86			public:
87	schoenebeck	319	BiquadFilter() {
88			Reset();
89			}
90
91			void Reset() {
92	schoenebeck	53	x1 = 0.0f;
93			x2 = 0.0f;
94			y1 = 0.0f;
95			y2 = 0.0f;
96			}
97
98			inline bq_t Apply(const bq_t x) {
99			bq_t y;
100
101			y = this->b0 * x + this->b1 * this->x1 + this->b2 * this->x2 +
102			this->a1 * this->y1 + this->a2 * this->y2;
103			KillDenormal(y);
104			this->x2 = this->x1;
105			this->x1 = x;
106			this->y2 = this->y1;
107			this->y1 = y;
108
109			return y;
110			}
111
112	schoenebeck	80	inline bq_t Apply(biquad_param_t* param, const bq_t x) {
113			bq_t y;
114
115			y = param->b0 * x + param->b1 * this->x1 + param->b2 * this->x2 +
116			param->a1 * this->y1 + param->a2 * this->y2;
117			KillDenormal(y);
118			this->x2 = this->x1;
119			this->x1 = x;
120			this->y2 = this->y1;
121			this->y1 = y;
122
123			return y;
124			}
125
126	schoenebeck	328	#if ARCH_X86
127	schoenebeck	319	// expects to find input in xmm0 (xmm0 stays unmodified) and finally leaves output in xmm6
128			inline void Apply4StepsSSE(biquad_param_t* param) {
129			__asm__ __volatile__ (
130			"movss (%2),%%xmm4 # b0\n\t"
131			"shufps $0x00,%%xmm4,%%xmm4 # copy b0 to other cells\n\t"
132			"mulps %%xmm0,%%xmm4 # xmm4 = x*b0\n\t"
133			"movups (%0),%%xmm2 # load b1,b2,a1,a2\n\t"
134			"movups (%1),%%xmm5 # load x1,x2,y1,y2\n\t"
135			/* sample 0 */
136			"movaps %%xmm5,%%xmm3\n\t"
137			"mulps %%xmm2,%%xmm5 # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
138			"shufps $0x0a,%%xmm3,%%xmm3 # x2 = x1, y2 = y1\n\t"
139			"movss %%xmm4,%%xmm6\n\t"
140			"addss %%xmm5,%%xmm6\n\t"
141			"shufps $0x39,%%xmm5,%%xmm5\n\t"
142			"addss %%xmm5,%%xmm6\n\t"
143			"shufps $0x39,%%xmm5,%%xmm5\n\t"
144			"addss %%xmm5,%%xmm6\n\t"
145			"shufps $0x39,%%xmm5,%%xmm5\n\t"
146			"addss %%xmm5,%%xmm6 # xmm6 = b0x + b1x1 + b2x2 + a1y1 + a2*y2\n\t"
147			/* sample 1 */
148			"shufps $0x39,%%xmm4,%%xmm4 # rotate xmm4 down 1 cell\n\t"
149			"movss %%xmm6,%%xmm3 # y1 = y\n\t"
150			"shufps $0x4e,%%xmm3,%%xmm3 # rotate 2 cells\n\t"
151			"movss %%xmm0,%%xmm3 # x1 = x\n\t"
152			"shufps $0x93,%%xmm6,%%xmm6 # rotate output up 1 cell\n\t"
153			"movaps %%xmm3,%%xmm5\n\t"
154			"shufps $0x39,%%xmm0,%%xmm0 # rotate input down 1 cell\n\t"
155			"mulps %%xmm2,%%xmm5 # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
156			"movss %%xmm5,%%xmm6\n\t"
157			"addss %%xmm4,%%xmm6\n\t"
158			"shufps $0x39,%%xmm5,%%xmm5\n\t"
159			"addss %%xmm5,%%xmm6\n\t"
160			"shufps $0x39,%%xmm5,%%xmm5\n\t"
161			"addss %%xmm5,%%xmm6\n\t"
162			"shufps $0x39,%%xmm5,%%xmm5\n\t"
163			"addss %%xmm5,%%xmm6 # xmm6 = b0x + b1x1 + b2x2 + a1y1 + a2*y2\n\t"
164			/* sample 2 */
165			"shufps $0x0a,%%xmm3,%%xmm3 # x2 = x1, y2 = y1\n\t"
166			"shufps $0x39,%%xmm4,%%xmm4 # rotate xmm4 down 1 cell\n\t"
167			"movss %%xmm6,%%xmm3 # y1 = y\n\t"
168			"shufps $0x4e,%%xmm3,%%xmm3 # rotate 2 cells\n\t"
169			"movss %%xmm0,%%xmm3 # x1 = x\n\t"
170			"shufps $0x93,%%xmm6,%%xmm6 # rotate output up 1 cell\n\t"
171			"movaps %%xmm3,%%xmm5\n\t"
172			"shufps $0x39,%%xmm0,%%xmm0 # rotate input down 1 cell\n\t"
173			"mulps %%xmm2,%%xmm5 # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
174			"movss %%xmm5,%%xmm6\n\t"
175			"addss %%xmm4,%%xmm6\n\t"
176			"shufps $0x39,%%xmm5,%%xmm5\n\t"
177			"addss %%xmm5,%%xmm6\n\t"
178			"shufps $0x39,%%xmm5,%%xmm5\n\t"
179			"addss %%xmm5,%%xmm6\n\t"
180			"shufps $0x39,%%xmm5,%%xmm5\n\t"
181			"addss %%xmm5,%%xmm6 # xmm6 = b0x + b1x1 + b2x2 + a1y1 + a2*y2\n\t"
182			/* sample 3 */
183			"shufps $0x0a,%%xmm3,%%xmm3 # x2 = x1, y2 = y1\n\t"
184			"shufps $0x39,%%xmm4,%%xmm4 # rotate xmm4 down 1 cell\n\t"
185			"movss %%xmm6,%%xmm3 # y1 = y\n\t"
186			"shufps $0x4e,%%xmm3,%%xmm3 # rotate 2 cells\n\t"
187			"movss %%xmm0,%%xmm3 # x1 = x\n\t"
188			"shufps $0x93,%%xmm6,%%xmm6 # rotate output up 1 cell\n\t"
189			"mulps %%xmm3,%%xmm2 # xmm5 = [b1,b2,a1,a2] * [x1,x2,y1,y2]\n\t"
190			"shufps $0x39,%%xmm0,%%xmm0 # rotate input down 1 cell\n\t"
191			"movss %%xmm2,%%xmm6\n\t"
192			"shufps $0x39,%%xmm2,%%xmm2\n\t"
193			"addss %%xmm2,%%xmm6\n\t"
194			"shufps $0x39,%%xmm2,%%xmm2\n\t"
195			"addss %%xmm2,%%xmm6\n\t"
196			"shufps $0x39,%%xmm2,%%xmm2\n\t"
197			"addss %%xmm2,%%xmm6\n\t"
198			"addss %%xmm4,%%xmm6 # xmm6 = b0x + b1x1 + b2x2 + a1y1 + a2*y2\n\t"
199			/* done */
200			"shufps $0x0a,%%xmm3,%%xmm3 # x2 = x1, y2 = y1\n\t"
201			"movss %%xmm6,%%xmm3 # y1 = y\n\t"
202			"shufps $0x4e,%%xmm3,%%xmm3 # rotate 2 cells\n\t"
203			"movss %%xmm0,%%xmm3 # x1 = x\n\t"
204			"shufps $0x1b,%%xmm6,%%xmm6 # swap output to correct order\n\t"
205			"shufps $0x39,%%xmm0,%%xmm0 # rotate input down 1 cell, to restore original input\n\t"
206			"movups %%xmm3,(%1) # store x1,x2,y1,y2\n\t"
207			: /* no output */
208			: "r" (&param->b1), /* %0 - [b1,b2,a1,a2] */
209			"r" (&x1), /* %1 - [x1,x2,y1,y2] */
210			"r" (&param->b0) /* %2 */
211			);
212			}
213	schoenebeck	328	#endif // ARCH_X86
214	schoenebeck	319
215	schoenebeck	53	inline bq_t ApplyFB(bq_t x, const bq_t fb) {
216			bq_t y;
217
218			x += this->y1 * fb * 0.98;
219			y = this->b0 * x + this->b1 * this->x1 + this->b2 * this->x2 +
220			this->a1 * this->y1 + this->a2 * this->y2;
221			KillDenormal(y);
222			this->x2 = this->x1;
223			this->x1 = x;
224			this->y2 = this->y1;
225			this->y1 = y;
226
227			return y;
228			}
229	schoenebeck	80
230			inline bq_t ApplyFB(biquad_param_t* param, bq_t x, const bq_t fb) {
231			bq_t y;
232
233			x += this->y1 * fb * 0.98;
234			y = param->b0 * x + param->b1 * this->x1 + param->b2 * this->x2 +
235			param->a1 * this->y1 + param->a2 * this->y2;
236			KillDenormal(y);
237			this->x2 = this->x1;
238			this->x1 = x;
239			this->y2 = this->y1;
240			this->y1 = y;
241
242			return y;
243			}
244	schoenebeck	319
245	schoenebeck	328	#if ARCH_X86
246	schoenebeck	319	// expects to find input in xmm0 (xmm0 stays unmodified) and finally leaves output in xmm7
247			inline void ApplyFB4StepsSSE(biquad_param_t* param, const bq_t &fb) {
248			float xs, ys;
249			float t0, t1, t2, t3, t4, t5, t6, t7, t8; // temporary stack space
250			__asm__ __volatile__ (
251			/* prepare input */
252			"movss %15,%%xmm5\n\t"
253			"movss %%xmm0,(%14)\n\t"
254			/* sample 0 */
255			"movss %0, %%xmm3\n\t"
256			"movss %1, %%xmm4\n\t"
257			"mulss %%xmm4, %%xmm5\n\t"
258			"movss %%xmm3, %2\n\t"
259			"movss %%xmm5, %16\n\t"
260			"mulss %%xmm3, %%xmm5\n\t"
261			"movss %19, %%xmm2\n\t"
262			"movss %3, %%xmm6\n\t"
263			"movss %21, %%xmm3\n\t"
264			"addss %%xmm5, %%xmm6\n\t"
265			"movss %%xmm2, %%xmm5\n\t"
266			"movss %20, %%xmm4\n\t"
267			"movss %%xmm6, %4\n\t"
268			"mulss %%xmm6, %%xmm5\n\t"
269			"movss %5, %%xmm6\n\t"
270			"movss %%xmm2, %6\n\t"
271			"movss %%xmm4, %7\n\t"
272			"movss %%xmm3, %%xmm2\n\t"
273			"mulss %%xmm6, %%xmm4\n\t"
274			"mulss %8, %%xmm2\n\t"
275			"movss %%xmm3, %9\n\t"
276			"addss %%xmm4, %%xmm5\n\t"
277			"movss %18, %%xmm3\n\t"
278			"movss %17, %%xmm4\n\t"
279			"addss %%xmm2, %%xmm5\n\t"
280			"movss %%xmm4, %10\n\t"
281			"movss %%xmm3, %%xmm2\n\t"
282			"mulss %11, %%xmm4\n\t"
283			"mulss %12, %%xmm2\n\t"
284			"movss %%xmm3, %13\n\t"
285			"addss %%xmm4, %%xmm5\n\t"
286			"movss %11, %%xmm3\n\t"
287			"movss %4, %%xmm4\n\t"
288			"addss %%xmm2, %%xmm5\n\t"
289			:: "m" (y1), /* %0 */
290			"m" (fbc), /* %1 */
291			"m" (t0), /* %2 */
292			"m" (xs), /* %3 */
293			"m" (t7), /* %4 */
294			"m" (x1), /* %5 */
295			"m" (t1), /* %6 */
296			"m" (t2), /* %7 */
297			"m" (x2), /* %8 */
298			"m" (t3), /* %9 */
299			"m" (t4), /* %10 */
300			"m" (t0), /* %11 */
301			"m" (y2), /* %12 */
302			"m" (t5), /* %13 */
303			"r" (&xs), /* %14 */
304			"m" (fb), /* %15 */
305			"m" (ys), /* %16 */
306			"m" (param->a1), /* %17 */
307			"m" (param->a2), /* %18 */
308			"m" (param->b0), /* %19 */
309			"m" (param->b1), /* %20 */
310			"m" (param->b2) /* %21 */
311			);
312			__asm__ __volatile__ (
313			"shufps $0x39,%%xmm0,%%xmm0 # rotate down one cell\n\t"
314			"movss %%xmm5,%%xmm7\n\t"
315			::
316			);
317			/* sample 1 */
318			__asm__ __volatile__ (
319			"movss %0, %%xmm4\n\t"
320			"movss %%xmm0, %%xmm3\n\t"
321			"mulss %%xmm5, %%xmm4\n\t"
322			"mulss %3, %%xmm6\n\t"
323			"movss %5, %%xmm2\n\t"
324			"addss %%xmm4, %%xmm3\n\t"
325			"mulss %7, %%xmm2\n\t"
326			"movss %6, %%xmm4\n\t"
327			"movss %%xmm3, %8\n\t"
328			"mulss %%xmm3, %%xmm4\n\t"
329			"addss %%xmm2, %%xmm4\n\t"
330			"movss %9, %%xmm3\n\t"
331			"mulss %%xmm5, %%xmm3\n\t"
332			"movss %10, %%xmm2\n\t"
333			"addss %%xmm6, %%xmm4\n\t"
334			"mulss %11, %%xmm2\n\t"
335			"addss %%xmm3, %%xmm4\n\t"
336			"addss %%xmm2, %%xmm4\n\t"
337			:: "m" (ys), /* %0 */
338			"m" (fbc), /* %1 */
339			"m" (xs), /* %2 */
340			"m" (t3), /* %3 */
341			"m" (y2), /* %4 */
342			"m" (t2), /* %5 */
343			"m" (t1), /* %6 */
344			"m" (t7), /* %7 */
345			"m" (t8), /* %8 */
346			"m" (t4), /* %9 */
347			"m" (t5), /* %10 */
348			"m" (t0), /* %11 */
349			"m" (x2), /* %12 */
350			"m" (x1), /* %13 */
351			"m" (y1) /* %14 */
352			);
353			__asm__ __volatile__ (
354			"shufps $0x93,%%xmm7,%%xmm7 # rotate up one cell\n\t"
355			"shufps $0x39,%%xmm0,%%xmm0 # rotate down one cell\n\t"
356			"movss %%xmm4,%%xmm7\n\t"
357			::
358			);
359			/* sample 2 */
360			__asm__ __volatile__ (
361			"movss %2, %%xmm6\n\t"
362			"movss %3, %%xmm3\n\t"
363			"mulss %%xmm4, %%xmm6\n\t"
364			"movss %4, %%xmm2\n\t"
365			"mulss %9, %%xmm2\n\t"
366			"addss %%xmm0, %%xmm6\n\t"
367			"mulss %7, %%xmm5\n\t"
368			"mulss %%xmm6, %%xmm3\n\t"
369			"addss %%xmm2, %%xmm3\n\t"
370			"movss %5, %%xmm2\n\t"
371			"mulss %8, %%xmm2\n\t"
372			"addss %%xmm2, %%xmm3\n\t"
373			"movss %6, %%xmm2\n\t"
374			"mulss %%xmm4, %%xmm2\n\t"
375			"addss %%xmm5, %%xmm2\n\t"
376			"addss %%xmm2, %%xmm3\n\t"
377			:: "m" (xs), /* %0 */
378			"m" (fb), /* %1 */
379			"m" (ys), /* %2 */
380			"m" (t1), /* %3 */
381			"m" (t2), /* %4 */
382			"m" (t3), /* %5 */
383			"m" (t4), /* %6 */
384			"m" (t5), /* %7 */
385			"m" (t7), /* %8 */
386			"m" (t8), /* %9 */
387			"m" (x1), /* %10 */
388			"m" (x2), /* %11 */
389			"m" (y1), /* %12 */
390			"m" (y2) /* %13 */
391			);
392			__asm__ __volatile__ (
393			"shufps $0x39,%%xmm0,%%xmm0 # rotate down one cell\n\t"
394			"shufps $0x93,%%xmm7,%%xmm7 # rotate up one cell\n\t"
395			"movss %%xmm3,%%xmm7\n\t"
396			::
397			);
398			/* sample 3 */
399			__asm__ __volatile__ (
400			"movss %1, %%xmm2\n\t"
401			"mulss %7, %%xmm4\n\t"
402			"mulss %%xmm3, %%xmm2\n\t"
403			"movss %3, %%xmm5\n\t"
404			"movss %%xmm6, %11\n\t"
405			"addss %%xmm0, %%xmm2\n\t"
406			"movss %%xmm3, %13\n\t"
407			"mulss %%xmm2, %%xmm5\n\t"
408			"mulss %4, %%xmm6\n\t"
409			"movss %%xmm2, %10\n\t"
410			"addss %%xmm6, %%xmm5\n\t"
411			"movss %5, %%xmm2\n\t"
412			"mulss %9, %%xmm2\n\t"
413			"mulss %6, %%xmm3\n\t"
414			"addss %%xmm2, %%xmm5\n\t"
415			"addss %%xmm3, %%xmm4\n\t"
416			"addss %%xmm4, %%xmm5\n\t"
417			"movss %%xmm5, %12\n\t"
418			:: "m" (xs), /* %0 */
419			"m" (ys), /* %1 */
420			"m" (fbc), /* %2 */
421			"m" (t1), /* %3 */
422			"m" (t2), /* %4 */
423			"m" (t3), /* %5 */
424			"m" (t4), /* %6 */
425			"m" (t5), /* %7 */
426			"m" (t6), /* %8 */
427			"m" (t8), /* %9 */
428			"m" (x1), /* %10 */
429			"m" (x2), /* %11 */
430			"m" (y1), /* %12 */
431			"m" (y2) /* %13 */
432			);
433			__asm__ __volatile__ (
434			"shufps $0x93,%%xmm7,%%xmm7 # rotate up one cell\n\t"
435			"shufps $0x39,%%xmm0,%%xmm0 # rotate down one cell to restore original input\n\t"
436			"movss %%xmm5,%%xmm7\n\t"
437			"shufps $0x1b,%%xmm7,%%xmm7 # swap output to correct order\n\t"
438			::
439			);
440			}
441	schoenebeck	53	};
442	schoenebeck	328	#endif // ARCH_X86
443	schoenebeck	53
444			class LowpassFilter : public BiquadFilter {
445			public:
446			inline LowpassFilter() : BiquadFilter() {}
447
448			inline void SetParameters(bq_t fc, bq_t bw, bq_t fs) {
449			bq_t omega = 2.0 * M_PI * fc / fs;
450			bq_t sn = sin(omega);
451			bq_t cs = cos(omega);
452			bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);
453
454			const float a0r = 1.0 / (1.0 + alpha);
455			this->b0 = a0r * (1.0 - cs) * 0.5;
456			this->b1 = a0r * (1.0 - cs);
457			this->b2 = a0r * (1.0 - cs) * 0.5;
458			this->a1 = a0r * (2.0 * cs);
459			this->a2 = a0r * (alpha - 1.0);
460			}
461	schoenebeck	80
462			inline void SetParameters(biquad_param_t* param, bq_t fc, bq_t bw, bq_t fs) {
463			bq_t omega = 2.0 * M_PI * fc / fs;
464			bq_t sn = sin(omega);
465			bq_t cs = cos(omega);
466			bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);
467
468			const float a0r = 1.0 / (1.0 + alpha);
469			param->b0 = a0r * (1.0 - cs) * 0.5;
470			param->b1 = a0r * (1.0 - cs);
471			param->b2 = a0r * (1.0 - cs) * 0.5;
472			param->a1 = a0r * (2.0 * cs);
473			param->a2 = a0r * (alpha - 1.0);
474			}
475	schoenebeck	53	};
476
477			class BandpassFilter : public BiquadFilter {
478			public:
479			inline BandpassFilter() : BiquadFilter() {}
480
481			inline void SetParameters(bq_t fc, bq_t bw, bq_t fs) {
482			bq_t omega = 2.0 * M_PI * fc / fs;
483			bq_t sn = sin(omega);
484			bq_t cs = cos(omega);
485			bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);
486
487			const float a0r = 1.0 / (1.0 + alpha);
488			this->b0 = a0r * alpha;
489			this->b1 = 0.0;
490			this->b2 = a0r * -alpha;
491			this->a1 = a0r * (2.0 * cs);
492			this->a2 = a0r * (alpha - 1.0);
493			}
494	schoenebeck	80
495			inline void SetParameters(biquad_param_t* param, bq_t fc, bq_t bw, bq_t fs) {
496			bq_t omega = 2.0 * M_PI * fc / fs;
497			bq_t sn = sin(omega);
498			bq_t cs = cos(omega);
499			bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);
500
501			const float a0r = 1.0 / (1.0 + alpha);
502			param->b0 = a0r * alpha;
503			param->b1 = 0.0;
504			param->b2 = a0r * -alpha;
505			param->a1 = a0r * (2.0 * cs);
506			param->a2 = a0r * (alpha - 1.0);
507			}
508	schoenebeck	53	};
509
510			class HighpassFilter : public BiquadFilter {
511			public:
512			inline HighpassFilter() : BiquadFilter() {}
513
514			inline void SetParameters(bq_t fc, bq_t bw, bq_t fs) {
515			bq_t omega = 2.0 * M_PI * fc / fs;
516			bq_t sn = sin(omega);
517			bq_t cs = cos(omega);
518			bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);
519
520			const float a0r = 1.0 / (1.0 + alpha);
521			this->b0 = a0r * (1.0 + cs) * 0.5;
522			this->b1 = a0r * -(1.0 + cs);
523			this->b2 = a0r * (1.0 + cs) * 0.5;
524			this->a1 = a0r * (2.0 * cs);
525			this->a2 = a0r * (alpha - 1.0);
526			}
527	schoenebeck	80
528			inline void SetParameters(biquad_param_t* param, bq_t fc, bq_t bw, bq_t fs) {
529			bq_t omega = 2.0 * M_PI * fc / fs;
530			bq_t sn = sin(omega);
531			bq_t cs = cos(omega);
532			bq_t alpha = sn * sinh(M_LN2 / 2.0 * bw * omega / sn);
533
534			const float a0r = 1.0 / (1.0 + alpha);
535			param->b0 = a0r * (1.0 + cs) * 0.5;
536			param->b1 = a0r * -(1.0 + cs);
537			param->b2 = a0r * (1.0 + cs) * 0.5;
538			param->a1 = a0r * (2.0 * cs);
539			param->a2 = a0r * (alpha - 1.0);
540			}
541	schoenebeck	53	};
542
543			} // namespace LinuxSampler
544
545			#endif // __LS_BIQUADFILTER_H__