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/*
* nfilterkit.c - windowed low-pass filter support.
* adapted from filterkit.c, by Julius Smith et al., CCRMA, Stanford University
*
/*
* FilterUp() - Applies a filter to a given sample when up-converting.
* FilterUD() - Applies a filter to a given sample when up- or down-
* converting.
*/
#include "soundstruct.h"
#include "nresample.h"
#include "nfilterkit.h"
/* #include <libc.h> */
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <math.h>
fast_float FilterUp(float Imp[], float ImpD[],
UHWORD Nwing, BOOL Interp,
float *Xp, double Ph, HWORD Inc)
{
float *Hp, *Hdp = NULL, *End;
fast_float a = 0;
fast_float v, t;
double exact_index = Ph * Npc;
long index = exact_index; /* convert fraction to filter index */
/* printf("FilterUp, Inc %d, phase %g\n", Inc, Ph); */
v=0;
Hp = &Imp[index];
End = &Imp[Nwing];
if (Interp) {
Hdp = &ImpD[index];
a = exact_index - index;
/* printf("fraction %g\n", a); */
}
if (Inc == 1) /* If doing right wing... */
{ /* ...drop extra coeff, so when Ph is */
End--; /* 0.5, we don't do too many mult's */
if (Ph == 0) /* If the phase is zero... */
{ /* ...then we've already skipped the */
printf("Ph == 0\n");
Hp += Npc; /* first sample, so we must also */
Hdp += Npc; /* skip ahead in Imp[] and ImpD[] */
}
}
if (Interp) {
while (Hp < End) {
t = *Hp; /* Get filter coeff */
/* t scaled by 2^(16 + NLpScl)/LpScl */
/* printf("coeff %g ", t); */
t += *Hdp *a; /* t is now interp'd filter coeff */
/* printf("interp'd coeff %g ", t);*/
Hdp += Npc; /* Filter coeff differences step */
/* printf("input sample %g ", *Xp); */
t *= *Xp; /* Mult coeff by input sample */
/* t scaled by 2^(16 + NLpScl)/LpScl */
/* printf("product %g\n", t); */
v += t; /* The filter output */
Hp += Npc; /* Filter coeff step */
Xp += Inc; /* Input signal step. NO CHECK ON BOUNDS */
}
} else {
while (Hp < End) {
t = *Hp; /* Get filter coeff */
t *= *Xp; /* Mult coeff by input sample */
v += t; /* The filter output */
Hp += Npc; /* Filter coeff step */
Xp += Inc; /* Input signal step. NO CHECK ON BOUNDS */
}
}
/* printf("FilterUp, Inc %d returns %g\n", Inc, v); */
return(v);
}
fast_float FilterUD( float Imp[], float ImpD[],
UHWORD Nwing, BOOL Interp,
float *Xp, double Ph, HWORD Inc, double dhb)
{
double a;
float *Hp, *Hdp, *End;
fast_float v, t;
double Ho;
v=0;
Ho = Ph*dhb;
End = &Imp[Nwing];
if (Inc == 1) /* If doing right wing... */
{ /* ...drop extra coeff, so when Ph is */
End--; /* 0.5, we don't do too many mult's */
if (Ph == 0) /* If the phase is zero... */
Ho += dhb; /* ...then we've already skipped the */
} /* first sample, so we must also */
/* skip ahead in Imp[] and ImpD[] */
if (Interp) {
long HoIndex = Ho;
while ((Hp = &Imp[HoIndex]) < End) {
t = *Hp; /* Get IR sample */
Hdp = &ImpD[HoIndex]; /* get interp (lower Na) bits from diff table*/
a = Ho - HoIndex; /* a is logically between 0 and 1 */
t += *Hdp * a; /* t is now interp'd filter coeff */
t *= *Xp; /* Mult coeff by input sample */
v += t; /* The filter output */
Ho += dhb; /* IR step */
Xp += Inc; /* Input signal step. NO CHECK ON BOUNDS */
HoIndex = Ho;
}
} else {
long HoIndex = Ho;
while ((Hp = &Imp[HoIndex]) < End) {
t = *Hp; /* Get IR sample */
t *= *Xp; /* Mult coeff by input sample */
v += t; /* The filter output */
Ho += dhb; /* IR step */
Xp += Inc; /* Input signal step. NO CHECK ON BOUNDS */
HoIndex = Ho;
}
}
return(v);
}
/* Sampling rate up-conversion only subroutine;
* Slightly faster than down-conversion;
*/
static int SrcUp(float X[], float Y[], double factor, double *Time,
UHWORD Nx, UHWORD Nwing, double LpScl,
float Imp[], float ImpD[], BOOL Interp)
{
mem_float *Xp, *Ystart;
fast_float v;
double dt; /* Step through input signal */
double endTime; /* When Time reaches EndTime, return to user */
/* printf("SrcUp: interpFilt %d\n", Interp);*/
dt = 1.0/factor; /* Output sampling period */
Ystart = Y;
endTime = *Time + Nx;
while (*Time < endTime)
{
long iTime = *Time;
Xp = &X[iTime]; /* Ptr to current input sample */
/* Perform left-wing inner product */
v = FilterUp(Imp, ImpD, Nwing, Interp, Xp, *Time - iTime, -1);
/* Perform right-wing inner product */
v += FilterUp(Imp, ImpD, Nwing, Interp, Xp+1,
(1 + iTime) - *Time, 1);
v *= LpScl; /* Normalize for unity filter gain */
/* printf("SrcUp output sample %g\n", v); */
*Y++ = v;
*Time += dt; /* Move to next sample by time increment */
}
return (Y - Ystart); /* Return the number of output samples */
}
/* Sampling rate conversion subroutine */
static int SrcUD(float X[], float Y[], double factor, double *Time,
UHWORD Nx, UHWORD Nwing, double LpScl,
float Imp[], float ImpD[], BOOL Interp)
{
mem_float *Xp, *Ystart;
fast_float v;
double dh; /* Step through filter impulse response */
double dt; /* Step through input signal */
double endTime; /* When Time reaches EndTime, return to user */
dt = 1.0/factor; /* Output sampling period */
dh = MIN(Npc, factor*Npc); /* Filter sampling period */
Ystart = Y;
endTime = *Time + Nx;
while (*Time < endTime)
{
long iTime = *Time;
Xp = &X[iTime]; /* Ptr to current input sample */
v = FilterUD(Imp, ImpD, Nwing, Interp, Xp, *Time - iTime,
-1, dh); /* Perform left-wing inner product */
v += FilterUD(Imp, ImpD, Nwing, Interp, Xp+1, (1 + iTime) - *Time,
1, dh); /* Perform right-wing inner product */
v *= LpScl; /* Normalize for unity filter gain */
*Y++ = v;
*Time += dt; /* Move to next sample by time increment */
}
return (Y - Ystart); /* Return the number of output samples */
}
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