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Added 8-point interpolation and new lowpass filter

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pagefault
2001-09-03 21:37:19 +00:00
parent ace679d23d
commit db6ce1cfd2
5 changed files with 719 additions and 119 deletions
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318
zsnes/src/zip/fir_proc.cpp Normal file
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/*
* This program is free software; you can redistribute it and modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the license or (at your
* option) any later version.
*
* Authors: Markus Fick <webmaster@mark-f.de> fir-resampler
* Chris Moeller <chris@kode54.net> C/C++ fir_interpolate functions based off original macros
*
*/
#include <math.h>
#ifndef log2
inline float log2(float f) {
float t;
#ifdef __GNUC__
__asm__ ("
fld1\n
fxch\n
fyl2x\n
fst (%1)"
:
: "st" (f), "r" (&t)
);
#else
__asm {
fld1
fld f
fyl2x
fstp t
}
#endif
return t;
}
#endif
/*
------------------------------------------------------------------------------------------------
fir interpolation doc,
(derived from "an engineer's guide to fir digital filters", n.j. loy)
calculate coefficients for ideal lowpass filter (with cutoff = fc in 0..1 (mapped to 0..nyquist))
c[-N..N] = (i==0) ? fc : sin(fc*pi*i)/(pi*i)
then apply selected window to coefficients
c[-N..N] *= w(0..N)
with n in 2*N and w(n) being a window function (see loy)
then calculate gain and scale filter coefs to have unity gain.
------------------------------------------------------------------------------------------------
*/
// quantizer scale of window coefs
#define WFIR_QUANTBITS 15
#define WFIR_QUANTSCALE (1L<<WFIR_QUANTBITS)
#define WFIR_8SHIFT (WFIR_QUANTBITS-8)
#define WFIR_16BITSHIFT (WFIR_QUANTBITS)
// log2(number)-1 of precalculated taps range is [4..12]
#define WFIR_FRACBITS 10
#define WFIR_LUTLEN ((1L<<(WFIR_FRACBITS+1))+1)
// number of samples in window
#define WFIR_LOG2WIDTH 3
#define WFIR_WIDTH (1L<<WFIR_LOG2WIDTH)
#define WFIR_SMPSPERWING ((WFIR_WIDTH-1)>>1)
// cutoff (1.0 == pi/2)
#define WFIR_CUTOFF 0.90f
#define WFIR_CUTOFFBITS 12
#define WFIR_CUTOFFLEN (1L<<(WFIR_CUTOFFBITS))
// wfir type
#define WFIR_HANN 0
#define WFIR_HAMMING 1
#define WFIR_BLACKMANEXACT 2
#define WFIR_BLACKMAN3T61 3
#define WFIR_BLACKMAN3T67 4
#define WFIR_BLACKMAN4T92 5
#define WFIR_BLACKMAN4T74 6
#define WFIR_KAISER4T 7
#define WFIR_TYPE WFIR_BLACKMANEXACT
// wfir help
#ifndef M_zPI
#define M_zPI 3.1415926535897932384626433832795
#endif
#define M_zEPS 1e-8
#define M_zBESSELEPS 1e-21
class CzWINDOWEDFIR
{ public:
CzWINDOWEDFIR( );
~CzWINDOWEDFIR( );
float coef( int _PCnr, float _POfs, float _PCut, int _PWidth, int _PType ) //float _PPos, float _PFc, int _PLen )
{ double _LWidthM1 = _PWidth-1;
double _LWidthM1Half = 0.5*_LWidthM1;
double _LPosU = ((double)_PCnr - _POfs);
double _LPos = _LPosU-_LWidthM1Half;
double _LPIdl = 2.0*M_zPI/_LWidthM1;
double _LWc,_LSi;
if( fabs(_LPos)<M_zEPS )
{ _LWc = 1.0;
_LSi = _PCut;
}
else
{ switch( _PType )
{ case WFIR_HANN:
_LWc = 0.50 - 0.50 * cos(_LPIdl*_LPosU);
break;
case WFIR_HAMMING:
_LWc = 0.54 - 0.46 * cos(_LPIdl*_LPosU);
break;
case WFIR_BLACKMANEXACT:
_LWc = 0.42 - 0.50 * cos(_LPIdl*_LPosU) + 0.08 * cos(2.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN3T61:
_LWc = 0.44959 - 0.49364 * cos(_LPIdl*_LPosU) + 0.05677 * cos(2.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN3T67:
_LWc = 0.42323 - 0.49755 * cos(_LPIdl*_LPosU) + 0.07922 * cos(2.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN4T92:
_LWc = 0.35875 - 0.48829 * cos(_LPIdl*_LPosU) + 0.14128 * cos(2.0*_LPIdl*_LPosU) - 0.01168 * cos(3.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN4T74:
_LWc = 0.40217 - 0.49703 * cos(_LPIdl*_LPosU) + 0.09392 * cos(2.0*_LPIdl*_LPosU) - 0.00183 * cos(3.0*_LPIdl*_LPosU);
break;
case WFIR_KAISER4T:
_LWc = 0.40243 - 0.49804 * cos(_LPIdl*_LPosU) + 0.09831 * cos(2.0*_LPIdl*_LPosU) - 0.00122 * cos(3.0*_LPIdl*_LPosU);
break;
default:
_LWc = 1.0;
break;
}
_LPos *= M_zPI;
_LSi = sin(_PCut*_LPos)/_LPos;
}
return (float)(_LWc*_LSi);
}
static signed int lut[WFIR_LUTLEN*WFIR_WIDTH];
static signed int lut_co[WFIR_CUTOFFLEN*WFIR_WIDTH];
};
signed int CzWINDOWEDFIR::lut[WFIR_LUTLEN*WFIR_WIDTH];
signed int CzWINDOWEDFIR::lut_co[WFIR_CUTOFFLEN*WFIR_WIDTH];
CzWINDOWEDFIR::CzWINDOWEDFIR()
{ int _LPcl;
float _LPcllen = (float)(1L<<WFIR_FRACBITS); // number of precalculated lines for 0..1 (-1..0)
float _LNorm = 1.0f / (float)(2.0f * _LPcllen);
float _LCut = WFIR_CUTOFF;
float _LScale = (float)WFIR_QUANTSCALE;
float _LGain,_LCoefs[WFIR_WIDTH];
for( _LPcl=0;_LPcl<WFIR_LUTLEN;_LPcl++ )
{
float _LOfs = ((float)_LPcl-_LPcllen)*_LNorm;
int _LCc,_LIdx = _LPcl<<WFIR_LOG2WIDTH;
for( _LCc=0,_LGain=0.0f;_LCc<WFIR_WIDTH;_LCc++ )
{ _LGain += (_LCoefs[_LCc] = coef( _LCc, _LOfs, _LCut, WFIR_WIDTH, WFIR_TYPE ));
}
_LGain = 1.0f/_LGain;
for( _LCc=0;_LCc<WFIR_WIDTH;_LCc++ )
{ float _LCoef = (float)floor( 0.5 + _LScale*_LCoefs[_LCc]*_LGain );
lut[_LIdx+_LCc] = (signed int)( (_LCoef<-_LScale)?-_LScale:((_LCoef>_LScale)?_LScale:_LCoef) );
}
}
for( _LPcl=0;_LPcl<WFIR_CUTOFFLEN;_LPcl++ )
{
int _LCc,_LIdx = _LPcl<<WFIR_LOG2WIDTH;
_LCut = WFIR_CUTOFF / (1.0f + ((float)_LPcl / (WFIR_CUTOFFLEN / 15.0f)));
for(_LCc=0,_LGain=0.0f;_LCc<WFIR_WIDTH;_LCc++ )
{
_LGain += (_LCoefs[_LCc] = coef( _LCc, -0.5f, _LCut, WFIR_WIDTH, WFIR_TYPE ));
}
_LGain = 1.0f/_LGain;
for( _LCc=0; _LCc<WFIR_WIDTH;_LCc++ )
{
float _LCoef = (float)floor( 0.5 + _LScale*_LCoefs[_LCc]*_LGain );
lut_co[_LIdx+_LCc] = (signed int)( (_LCoef<-_LScale)?-_LScale:((_LCoef>_LScale)?_LScale:_LCoef) );
}
}
}
CzWINDOWEDFIR::~CzWINDOWEDFIR()
{ // nothing todo
}
/*
float coef( int _PCnr, float _POfs, float _PCut, int _PWidth, int _PType ) //float _PPos, float _PFc, int _PLen )
{
double _LWidthM1 = _PWidth-1;
double _LWidthM1Half = 0.5*_LWidthM1;
double _LPosU = ((double)_PCnr - _POfs);
double _LPos = _LPosU-_LWidthM1Half;
double _LPIdl = 2.0*M_zPI/_LWidthM1;
double _LWc,_LSi;
if( fabs(_LPos)<M_zEPS )
{ _LWc = 1.0;
_LSi = _PCut;
}
else
{ switch( _PType )
{ case WFIR_HANN:
_LWc = 0.50 - 0.50 * cos(_LPIdl*_LPosU);
break;
case WFIR_HAMMING:
_LWc = 0.54 - 0.46 * cos(_LPIdl*_LPosU);
break;
case WFIR_BLACKMANEXACT:
_LWc = 0.42 - 0.50 * cos(_LPIdl*_LPosU) + 0.08 * cos(2.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN3T61:
_LWc = 0.44959 - 0.49364 * cos(_LPIdl*_LPosU) + 0.05677 * cos(2.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN3T67:
_LWc = 0.42323 - 0.49755 * cos(_LPIdl*_LPosU) + 0.07922 * cos(2.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN4T92:
_LWc = 0.35875 - 0.48829 * cos(_LPIdl*_LPosU) + 0.14128 * cos(2.0*_LPIdl*_LPosU) - 0.01168 * cos(3.0*_LPIdl*_LPosU);
break;
case WFIR_BLACKMAN4T74:
_LWc = 0.40217 - 0.49703 * cos(_LPIdl*_LPosU) + 0.09392 * cos(2.0*_LPIdl*_LPosU) - 0.00183 * cos(3.0*_LPIdl*_LPosU);
break;
case WFIR_KAISER4T:
_LWc = 0.40243 - 0.49804 * cos(_LPIdl*_LPosU) + 0.09831 * cos(2.0*_LPIdl*_LPosU) - 0.00122 * cos(3.0*_LPIdl*_LPosU);
break;
default:
_LWc = 1.0;
break;
}
_LPos *= M_zPI;
_LSi = sin(_PCut*_LPos)/_LPos;
}
return (float)(_LWc*_LSi);
}
*/
CzWINDOWEDFIR sfir;
// fir interpolation
#define WFIR_FRACSHIFT (16-(WFIR_FRACBITS+1+WFIR_LOG2WIDTH))
#define WFIR_FRACMASK ((((1L<<(17-WFIR_FRACSHIFT))-1)&~((1L<<WFIR_LOG2WIDTH)-1)))
#define WFIR_FRACHALVE (1L<<(16-(WFIR_FRACBITS+2)))
inline int __fir_interpolate(unsigned int nPos, int *p)
{
int poshi = nPos >> 24;
int poslo = ((nPos >> 8) & 0xFFFF);
int firidx = ((poslo+WFIR_FRACHALVE)>>WFIR_FRACSHIFT) & WFIR_FRACMASK;
int vol = (CzWINDOWEDFIR::lut[firidx+0]*p[poshi+0]);
vol += (CzWINDOWEDFIR::lut[firidx+1]*p[poshi+1]);
vol += (CzWINDOWEDFIR::lut[firidx+2]*p[poshi+2]);
vol += (CzWINDOWEDFIR::lut[firidx+3]*p[poshi+3]);
vol += (CzWINDOWEDFIR::lut[firidx+4]*p[poshi+4]);
vol += (CzWINDOWEDFIR::lut[firidx+5]*p[poshi+5]);
vol += (CzWINDOWEDFIR::lut[firidx+6]*p[poshi+6]);
vol += (CzWINDOWEDFIR::lut[firidx+7]*p[poshi+7]);
vol >>= WFIR_16BITSHIFT;
return vol;
}
extern "C" int fir_interpolate(unsigned int nPos, int *p)
{
return __fir_interpolate(nPos, p);
}
#define WFIR_CUTOFFSHIFT (32-(WFIR_CUTOFFBITS+WFIR_LOG2WIDTH))
#define WFIR_CUTOFFMASK ((((1L<<(32-WFIR_CUTOFFSHIFT))-1)&~((1L<<WFIR_LOG2WIDTH)-1)))
#define WFIR_CUTOFFHALVE (1L<<(32-(WFIR_CUTOFFBITS+1)))
inline void __fir_downsample(unsigned int freq, signed int *p, signed short *out)
{
/*
float cutoff = WFIR_CUTOFF / (1.0f + log2((float)freq / 16777216.0f));
float _LGain, _LCoefs[WFIR_WIDTH];
int _LCc;
for(_LCc=0,_LGain=0.0f;_LCc<WFIR_WIDTH;_LCc++ )
{
_LGain += (_LCoefs[_LCc] = coef( _LCc, -0.5f, cutoff, WFIR_WIDTH, WFIR_TYPE ));
}
_LGain = 1.0f/_LGain;
for(int ct=0;ct<16;ct++)
{
signed int vol;
float acc = (_LCoefs[0] * _LGain * (float)p[ct+0]);
acc += (_LCoefs[1] * _LGain * (float)p[ct+1]);
acc += (_LCoefs[2] * _LGain * (float)p[ct+2]);
acc += (_LCoefs[3] * _LGain * (float)p[ct+3]);
acc += (_LCoefs[4] * _LGain * (float)p[ct+4]);
acc += (_LCoefs[5] * _LGain * (float)p[ct+5]);
acc += (_LCoefs[6] * _LGain * (float)p[ct+6]);
acc += (_LCoefs[7] * _LGain * (float)p[ct+7]);
vol = (signed int)acc;
if (vol > 32767) vol=32767;
else if (vol < -32768) vol=-32768;
out[ct]=(signed short)vol;
}
*/
int firidx = (((freq-16777216)+WFIR_CUTOFFHALVE)>>WFIR_CUTOFFSHIFT) & WFIR_CUTOFFMASK;
for(int ct=0;ct<16;ct++)
{
int vol = (CzWINDOWEDFIR::lut_co[firidx+0]*p[ct+0]);
vol += (CzWINDOWEDFIR::lut_co[firidx+1]*p[ct+1]);
vol += (CzWINDOWEDFIR::lut_co[firidx+2]*p[ct+2]);
vol += (CzWINDOWEDFIR::lut_co[firidx+3]*p[ct+3]);
vol += (CzWINDOWEDFIR::lut_co[firidx+4]*p[ct+4]);
vol += (CzWINDOWEDFIR::lut_co[firidx+5]*p[ct+5]);
vol += (CzWINDOWEDFIR::lut_co[firidx+6]*p[ct+6]);
vol += (CzWINDOWEDFIR::lut_co[firidx+7]*p[ct+7]);
vol >>= WFIR_16BITSHIFT;
if (vol > 32767) vol=32767;
else if (vol < -32768) vol=-32768;
out[ct]=(signed short)vol;
}
}
extern "C" void fir_downsample(unsigned int freq, signed int *p, signed short *out)
{
__fir_downsample(freq, p, out);
}