/**
ConvertToInterpolationCoefficients
@param c Input samples --> output coefficients
@param DataLength Number of samples or coefficients
@param z Poles
@param NbPoles Number of poles
@param Tolerance Admissible relative error
*/
static void
ConvertToInterpolationCoefficients(double *c, long DataLength, double *z, long NbPoles, double Tolerance) {
double Lambda = 1;
long n, k;
// special case required by mirror boundaries
if(DataLength == 1L) {
return;
}
// compute the overall gain
for(k = 0L; k < NbPoles; k++) {
Lambda = Lambda * (1.0 - z[k]) * (1.0 - 1.0 / z[k]);
}
// apply the gain
for (n = 0L; n < DataLength; n++) {
c[n] *= Lambda;
}
// loop over all poles
for (k = 0L; k < NbPoles; k++) {
// causal initialization
c[0] = InitialCausalCoefficient(c, DataLength, z[k], Tolerance);
// causal recursion
for (n = 1L; n < DataLength; n++) {
c[n] += z[k] * c[n - 1L];
}
// anticausal initialization
c[DataLength - 1L] = InitialAntiCausalCoefficient(c, DataLength, z[k]);
// anticausal recursion
for (n = DataLength - 2L; 0 <= n; n--) {
c[n] = z[k] * (c[n + 1L] - c[n]);
}
}
}
/*--------------------------------------------------------------------------*/
static void ConvertToInterpolationCoefficients
(
double c[], /* input samples --> output coefficients */
long DataLength, /* number of samples or coefficients */
double z[], /* poles */
long NbPoles, /* number of poles */
double Tolerance /* admissible relative error */
)
{ /* begin ConvertToInterpolationCoefficients */
double Lambda = 1.0;
long n, k;
/* special case required by mirror boundaries */
if (DataLength == 1L)
{
return;
}
/* compute the overall gain */
for (k = 0L; k < NbPoles; k++)
{
Lambda = Lambda * (1.0 - z[k]) * (1.0 - 1.0 / z[k]);
}
/* apply the gain */
for (n = 0L; n < DataLength; n++)
{
c[n] *= Lambda;
}
/* loop over all poles */
for (k = 0L; k < NbPoles; k++)
{
/* causal initialization */
c[0] = InitialCausalCoefficient(c, DataLength, z[k], Tolerance);
/* causal recursion */
for (n = 1L; n < DataLength; n++)
{
c[n] += z[k] * c[n - 1L];
}
/* anticausal initialization */
c[DataLength - 1L] = InitialAntiCausalCoefficient(c, DataLength, z[k]);
/* anticausal recursion */
for (n = DataLength - 2L; 0 <= n; n--)
{
c[n] = z[k] * (c[n + 1L] - c[n]);
}
}
} /* end ConvertToInterpolationCoefficients */
