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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 _PCnr, double _POfs, double _PCut, int _PWidth, int _PType ) //float _PPos, float _PFc, int _PLen )
{
const double epsilon = 1e-8;
const double _LWidthM1 = _PWidth - 1;
const double _LWidthM1Half = 0.5 * _LWidthM1;
const double _LPosU = (_PCnr - _POfs);
const double _LPIdl = (2.0 * mpt::numbers::pi) / _LWidthM1;
double _LPos = _LPosU - _LWidthM1Half;
double _LWc, _LSi;
if(std::abs(_LPos) < epsilon)
{
_LWc = 1.0;
_LSi = _PCut;
} else
{
switch(_PType)
{
case WFIR_HANN:
_LWc = 0.50 - 0.50 * std::cos(_LPIdl * _LPosU);
break;
case WFIR_HAMMING:
_LWc = 0.54 - 0.46 * std::cos(_LPIdl * _LPosU);
break;
case WFIR_BLACKMANEXACT:
_LWc = 0.42 - 0.50 * std::cos(_LPIdl * _LPosU) + 0.08 * std::cos(2.0 * _LPIdl * _LPosU);
break;
case WFIR_BLACKMAN3T61:
_LWc = 0.44959 - 0.49364 * std::cos(_LPIdl * _LPosU) + 0.05677 * std::cos(2.0 * _LPIdl * _LPosU);
break;
case WFIR_BLACKMAN3T67:
_LWc = 0.42323 - 0.49755 * std::cos(_LPIdl * _LPosU) + 0.07922 * std::cos(2.0 * _LPIdl * _LPosU);
break;
case WFIR_BLACKMAN4T92: // blackman harris
_LWc = 0.35875 - 0.48829 * std::cos(_LPIdl * _LPosU) + 0.14128 * std::cos(2.0 * _LPIdl * _LPosU) - 0.01168 * std::cos(3.0 * _LPIdl * _LPosU);
break;
case WFIR_BLACKMAN4T74:
_LWc = 0.40217 - 0.49703 * std::cos(_LPIdl * _LPosU) + 0.09392 * std::cos(2.0 * _LPIdl * _LPosU) - 0.00183 * std::cos(3.0 * _LPIdl * _LPosU);
break;
case WFIR_KAISER4T: // kaiser-bessel, alpha~7.5
_LWc = 0.40243 - 0.49804 * std::cos(_LPIdl * _LPosU) + 0.09831 * std::cos(2.0 * _LPIdl * _LPosU) - 0.00122 * std::cos(3.0 * _LPIdl * _LPosU);
break;
default:
_LWc = 1.0;
break;
}
_LPos *= mpt::numbers::pi;
_LSi = std::sin(_PCut * _LPos) / _LPos;
}
return (_LWc * _LSi);
}
void CWindowedFIR::InitTable(double WFIRCutoff, uint8 WFIRType)
{
const double _LPcllen = (double)(1 << WFIR_FRACBITS); // number of precalculated lines for 0..1 (-1..0)
const double _LNorm = 1.0 / (2.0 * _LPcllen);
const double _LCut = WFIRCutoff;
for(int _LPcl = 0; _LPcl < WFIR_LUTLEN; _LPcl++)
{
double _LGain = 0.0, _LCoefs[WFIR_WIDTH];
const double _LOfs = (_LPcl - _LPcllen) * _LNorm;
const int _LIdx = _LPcl << WFIR_LOG2WIDTH;
for(int _LCc = 0; _LCc < WFIR_WIDTH; _LCc++)
{
_LGain += (_LCoefs[_LCc] = coef(_LCc, _LOfs, _LCut, WFIR_WIDTH, WFIRType));
}
_LGain = 1.0 / _LGain;
for(int _LCc = 0; _LCc < WFIR_WIDTH; _LCc++)
{
#ifdef MPT_INTMIXER
double _LCoef = std::floor(0.5 + WFIR_QUANTSCALE * _LCoefs[_LCc] * _LGain);
lut[_LIdx + _LCc] = (signed short)((_LCoef < -WFIR_QUANTSCALE) ? -WFIR_QUANTSCALE : ((_LCoef > WFIR_QUANTSCALE) ? WFIR_QUANTSCALE : _LCoef));
#else
double _LCoef = _LCoefs[_LCc] * _LGain;
lut[_LIdx + _LCc] = (float)_LCoef;
#endif // MPT_INTMIXER
}
}
}
OPENMPT_NAMESPACE_END
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