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/*
butter.c:
Copyright (C) 1994 Paris Smaragdis, John ffitch
This file is part of Csound.
The Csound Library is free software; you can redistribute it
and/or modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
Csound 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with Csound; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
02110-1301 USA
*/
/* Butterworth filters coded by Paris Smaragdis 1994 */
/* Berklee College of Music Csound development team */
/* Copyright (c) May 1994. All rights reserved */
#include "stdopcod.h"
typedef struct {
OPDS h;
MYFLT *sr, *ain, *kfc, *istor;
MYFLT lkf;
double a[8];
} BFIL;
typedef struct {
OPDS h;
MYFLT *sr, *ain, *kfo, *kbw, *istor;
MYFLT lkf, lkb;
double a[8];
} BBFIL;
#include <math.h>
//#define ROOT2 (1.4142135623730950488)
static void butter_filter(uint32_t, uint32_t, MYFLT *, MYFLT *, double *);
int32_t butset(CSOUND *csound, BFIL *p) /* Hi/Lo pass set-up */
{
IGN(csound);
if (*p->istor==FL(0.0)) {
p->a[6] = p->a[7] = 0.0;
p->lkf = FL(0.0);
}
return OK;
}
static int32_t hibut(CSOUND *csound, BFIL *p) /* Hipass filter */
{
MYFLT *out, *in;
uint32_t offset = p->h.insdshead->ksmps_offset;
uint32_t early = p->h.insdshead->ksmps_no_end;
uint32_t nsmps = CS_KSMPS;
in = p->ain;
out = p->sr;
if (UNLIKELY(offset)) memset(out, '\0', offset*sizeof(MYFLT));
if (UNLIKELY(early)) {
nsmps -= early;
memset(&out[nsmps], '\0', early*sizeof(MYFLT));
}
if (*p->kfc <= FL(0.0)) {
memcpy(&out[offset], &in[offset], (nsmps-offset)*sizeof(MYFLT));
return OK;
}
if (*p->kfc != p->lkf) {
double *a, c;
a = p->a;
p->lkf = *p->kfc;
c = tan((double)(csound->pidsr * p->lkf));
a[1] = 1.0 / ( 1.0 + ROOT2 * c + c * c);
a[2] = -(a[1] + a[1]);
a[3] = a[1];
a[4] = 2.0 * ( c*c - 1.0) * a[1];
a[5] = ( 1.0 - ROOT2 * c + c * c) * a[1];
}
butter_filter(nsmps, offset, in, out, p->a);
return OK;
}
static int32_t lobut(CSOUND *csound, BFIL *p) /* Lopass filter */
{
MYFLT *out, *in;
uint32_t offset = p->h.insdshead->ksmps_offset;
uint32_t early = p->h.insdshead->ksmps_no_end;
uint32_t nsmps = CS_KSMPS;
in = p->ain;
out = p->sr;
if (*p->kfc <= FL(0.0)) {
memset(out, 0, nsmps*sizeof(MYFLT));
return OK;
}
if (UNLIKELY(offset)) memset(out, '\0', offset*sizeof(MYFLT));
if (UNLIKELY(early)) {
nsmps -= early;
memset(&out[nsmps], '\0', early*sizeof(MYFLT));
}
if (*p->kfc != p->lkf) {
double *a, c;
a = p->a;
p->lkf = *p->kfc;
c = 1.0 / tan((double)(csound->pidsr * p->lkf));
a[1] = 1.0 / ( 1.0 + ROOT2 * c + c * c);
a[2] = a[1] + a[1];
a[3] = a[1];
a[4] = 2.0 * ( 1.0 - c*c) * a[1];
a[5] = ( 1.0 - ROOT2 * c + c * c) * a[1];
}
butter_filter(nsmps, offset, in, out, p->a);
return OK;
}
/* Filter loop */
static void butter_filter(uint32_t n, uint32_t offset,
MYFLT *in, MYFLT *out, double *a)
{
double t, y;
uint32_t nn;
for (nn=offset; nn<n; nn++) {
t = (double)in[nn] - a[4] * a[6] - a[5] * a[7];
t = csoundUndenormalizeDouble(t); /* Not needed on AMD */
y = t * a[1] + a[2] * a[6] + a[3] * a[7];
a[7] = a[6];
a[6] = t;
out[nn] = (MYFLT)y;
}
}
#define S(x) sizeof(x)
static OENTRY localops[] = {
{ "butterhp.k", S(BFIL), 0, 3, "a", "ako", (SUBR)butset, (SUBR)hibut },
{ "butterlp.k", S(BFIL), 0, 3, "a", "ako", (SUBR)butset, (SUBR)lobut },
{ "buthp.k", S(BFIL), 0, 3, "a", "ako", (SUBR)butset, (SUBR)hibut },
{ "butlp.k", S(BFIL), 0, 3, "a", "ako", (SUBR)butset, (SUBR)lobut },
};
int32_t butter_init_(CSOUND *csound)
{
return csound->AppendOpcodes(csound, &(localops[0]),
(int32_t
) (sizeof(localops) / sizeof(OENTRY)));
}
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