FIRFilter::FIRFilter(double beta, double gamma, double cutoff)
{
int pointer, increment, numberCoefficients;
double coefficient[LIMIT + 1];
/* DETERMINE IDEAL LOW PASS FILTER COEFFICIENTS */
maximallyFlat(beta, gamma, &numberCoefficients, coefficient);
/* TRIM LOW-VALUE COEFFICIENTS */
trim(cutoff, &numberCoefficients, coefficient);
/* DETERMINE THE NUMBER OF TAPS IN THE FILTER */
numberTaps_ = (numberCoefficients * 2) - 1;
/* ALLOCATE MEMORY FOR DATA AND COEFFICIENTS */
data_.resize(numberTaps_);
coef_.resize(numberTaps_);
/* INITIALIZE THE COEFFICIENTS */
increment = -1;
pointer = numberCoefficients;
for (int i = 0; i < numberTaps_; i++) {
coef_[i] = coefficient[pointer];
pointer += increment;
if (pointer <= 0) {
pointer = 2;
increment = 1;
}
}
/* SET POINTER TO FIRST ELEMENT */
ptr_ = 0;
#if 0
/* PRINT OUT */
printf("\n");
for (int i = 0; i < numberTaps_; i++) {
printf("coef_[%-d] = %11.8f\n", i, coef_[i]);
}
#endif
}
TRMFIRFilter *TRMFIRFilterCreate(double beta, double gamma, double cutoff)
{
TRMFIRFilter *newFilter;
int i, pointer, increment, numberCoefficients;
double coefficient[LIMIT+1];
newFilter = (TRMFIRFilter *)malloc(sizeof(TRMFIRFilter));
if (newFilter == NULL) {
fprintf(stderr, "Couldn't malloc() FIRFilter.\n");
return NULL;
}
/* DETERMINE IDEAL LOW PASS FILTER COEFFICIENTS */
maximallyFlat(beta, gamma, &numberCoefficients, coefficient);
/* TRIM LOW-VALUE COEFFICIENTS */
trim(cutoff, &numberCoefficients, coefficient);
/* DETERMINE THE NUMBER OF TAPS IN THE FILTER */
newFilter->numberTaps = (numberCoefficients * 2) - 1;
/* ALLOCATE MEMORY FOR DATA AND COEFFICIENTS */
newFilter->FIRData = (double *)calloc(newFilter->numberTaps, sizeof(double));
if (newFilter->FIRData == NULL) {
fprintf(stderr, "calloc() of FIRData failed.\n");
free(newFilter);
return NULL;
}
newFilter->FIRCoef = (double *)calloc(newFilter->numberTaps, sizeof(double));
if (newFilter->FIRCoef == NULL) {
fprintf(stderr, "calloc() of FIRCoef failed.\n");
free(newFilter->FIRData);
free(newFilter);
return NULL;
}
/* INITIALIZE THE COEFFICIENTS */
increment = -1;
pointer = numberCoefficients;
for (i = 0; i < newFilter->numberTaps; i++) {
newFilter->FIRCoef[i] = coefficient[pointer];
pointer += increment;
if (pointer <= 0) {
pointer = 2;
increment = 1;
}
}
/* SET POINTER TO FIRST ELEMENT */
newFilter->FIRPtr = 0;
#if DEBUG
/* PRINT OUT */
printf("\n");
for (i = 0; i < newFilter->numberTaps; i++)
printf("FIRCoef[%-d] = %11.8f\n", i, newFilter->FIRCoef[i]);
#endif
return newFilter;
}
