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/*
* WindowedFIR.cpp
* ---------------
* Purpose: FIR resampling code
* Notes : Original code from modplug-xmms
* Authors: OpenMPT Devs
* ModPlug-XMMS Devs
* The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
*/
#include "stdafx.h"
#include "WindowedFIR.h"
#include "mpt/base/numbers.hpp"
#include <cmath>
OPENMPT_NAMESPACE_BEGIN
double CWindowedFIR::coef(int cnr, double ofs, double cut, int width, int type)
{
const double epsilon = 1e-8;
const double widthM1 = width - 1;
const double widthM1Half = 0.5 * widthM1;
const double posU = (cnr - ofs);
const double idl = (2.0 * mpt::numbers::pi) / widthM1;
double pos = posU - widthM1Half;
double wc, si;
if(std::abs(pos) < epsilon)
{
wc = 1.0;
si = cut;
} else
{
switch(type)
{
case WFIR_HANN:
wc = 0.50 - 0.50 * std::cos(idl * posU);
break;
case WFIR_HAMMING:
wc = 0.54 - 0.46 * std::cos(idl * posU);
break;
case WFIR_BLACKMANEXACT:
wc = 0.42 - 0.50 * std::cos(idl * posU) + 0.08 * std::cos(2.0 * idl * posU);
break;
case WFIR_BLACKMAN3T61:
wc = 0.44959 - 0.49364 * std::cos(idl * posU) + 0.05677 * std::cos(2.0 * idl * posU);
break;
case WFIR_BLACKMAN3T67:
wc = 0.42323 - 0.49755 * std::cos(idl * posU) + 0.07922 * std::cos(2.0 * idl * posU);
break;
case WFIR_BLACKMAN4T92: // blackman harris
wc = 0.35875 - 0.48829 * std::cos(idl * posU) + 0.14128 * std::cos(2.0 * idl * posU) - 0.01168 * std::cos(3.0 * idl * posU);
break;
case WFIR_BLACKMAN4T74:
wc = 0.40217 - 0.49703 * std::cos(idl * posU) + 0.09392 * std::cos(2.0 * idl * posU) - 0.00183 * std::cos(3.0 * idl * posU);
break;
case WFIR_KAISER4T: // kaiser-bessel, alpha~7.5
wc = 0.40243 - 0.49804 * std::cos(idl * posU) + 0.09831 * std::cos(2.0 * idl * posU) - 0.00122 * std::cos(3.0 * idl * posU);
break;
default:
wc = 1.0;
break;
}
pos *= mpt::numbers::pi;
si = std::sin(cut * pos) / pos;
}
return (wc * si);
}
void CWindowedFIR::InitTable(double WFIRCutoff, uint8 WFIRType)
{
const double pcllen = (double)(1 << WFIR_FRACBITS); // number of precalculated lines for 0..1 (-1..0)
const double norm = 1.0 / (2.0 * pcllen);
const double cut = WFIRCutoff;
for(int pcl = 0; pcl < WFIR_LUTLEN; pcl++)
{
double gain = 0.0, coefs[WFIR_WIDTH];
const double ofs = (pcl - pcllen) * norm;
const int idx = pcl << WFIR_LOG2WIDTH;
for(int cc = 0; cc < WFIR_WIDTH; cc++)
{
gain += (coefs[cc] = coef(cc, ofs, cut, WFIR_WIDTH, WFIRType));
}
gain = 1.0 / gain;
for(int cc = 0; cc < WFIR_WIDTH; cc++)
{
#ifdef MPT_INTMIXER
double coef = std::floor(0.5 + WFIR_QUANTSCALE * coefs[cc] * gain);
lut[idx + cc] = (signed short)((coef < -WFIR_QUANTSCALE) ? -WFIR_QUANTSCALE : ((coef > WFIR_QUANTSCALE) ? WFIR_QUANTSCALE : coef));
#else
double coef = coefs[cc] * gain;
lut[idx + cc] = (float)coef;
#endif // MPT_INTMIXER
}
}
}
OPENMPT_NAMESPACE_END
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