/usr/share/doc/libclam-doc/examples/TickExtractor/libresample-0.1.3/src/resamplesubs.c is in libclam-doc 1.4.0-5.2.
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resamplesubs.c
Real-time library interface by Dominic Mazzoni
Based on resample-1.7:
http://www-ccrma.stanford.edu/~jos/resample/
License: LGPL - see the file LICENSE.txt for more information
This file provides the routines that do sample-rate conversion
on small arrays, calling routines from filterkit.
**********************************************************************/
/* Definitions */
#include "resample_defs.h"
#include "filterkit.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <string.h>
/* Sampling rate up-conversion only subroutine;
* Slightly faster than down-conversion;
*/
int lrsSrcUp(float X[],
float Y[],
double factor,
double *TimePtr,
UWORD Nx,
UWORD Nwing,
float LpScl,
float Imp[],
float ImpD[],
BOOL Interp)
{
float *Xp, *Ystart;
float v;
double CurrentTime = *TimePtr;
double dt; /* Step through input signal */
double endTime; /* When Time reaches EndTime, return to user */
dt = 1.0/factor; /* Output sampling period */
Ystart = Y;
endTime = CurrentTime + Nx;
while (CurrentTime < endTime)
{
double LeftPhase = CurrentTime-floor(CurrentTime);
double RightPhase = 1.0 - LeftPhase;
Xp = &X[(int)CurrentTime]; /* Ptr to current input sample */
/* Perform left-wing inner product */
v = lrsFilterUp(Imp, ImpD, Nwing, Interp, Xp,
LeftPhase, -1);
/* Perform right-wing inner product */
v += lrsFilterUp(Imp, ImpD, Nwing, Interp, Xp+1,
RightPhase, 1);
v *= LpScl; /* Normalize for unity filter gain */
*Y++ = v; /* Deposit output */
CurrentTime += dt; /* Move to next sample by time increment */
}
*TimePtr = CurrentTime;
return (Y - Ystart); /* Return the number of output samples */
}
/* Sampling rate conversion subroutine */
int lrsSrcUD(float X[],
float Y[],
double factor,
double *TimePtr,
UWORD Nx,
UWORD Nwing,
float LpScl,
float Imp[],
float ImpD[],
BOOL Interp)
{
float *Xp, *Ystart;
float v;
double CurrentTime = (*TimePtr);
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 = CurrentTime + Nx;
while (CurrentTime < endTime)
{
double LeftPhase = CurrentTime-floor(CurrentTime);
double RightPhase = 1.0 - LeftPhase;
Xp = &X[(int)CurrentTime]; /* Ptr to current input sample */
/* Perform left-wing inner product */
v = lrsFilterUD(Imp, ImpD, Nwing, Interp, Xp,
LeftPhase, -1, dh);
/* Perform right-wing inner product */
v += lrsFilterUD(Imp, ImpD, Nwing, Interp, Xp+1,
RightPhase, 1, dh);
v *= LpScl; /* Normalize for unity filter gain */
*Y++ = v; /* Deposit output */
CurrentTime += dt; /* Move to next sample by time increment */
}
*TimePtr = CurrentTime;
return (Y - Ystart); /* Return the number of output samples */
}
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