filter_templates.h
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/*
* Extended Audio Converter for SDL (Simple DirectMedia Layer)
* Copyright (C) 2002 Frank Ranostaj
* Institute of Applied Physik
* Johann Wolfgang Goethe-Universität
* Frankfurt am Main, Germany
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Frank Ranostaj
* ranostaj@stud.uni-frankfurt.de
*
* (This code blatantly abducted for SDL_sound. Thanks, Frank! --ryan.)
*/
#ifndef Suffix
#error include filter_template.h with defined Suffix macro!
#else
#define CH(x) (Suffix((x)*))
/*-------------------------------------------------------------------------*/
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/* this filter (Kaiser-window beta=6.8) gives a decent -80dB attentuation */
/*-------------------------------------------------------------------------*/
#define sum_d(v,dx) ((int) v[CH(dx)] + v[CH(1-dx)])
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static Sint16* Suffix(doubleRate)( Sint16 *outp, Sint16 *inp, int length,
VarFilter* filt, int* cpos )
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{
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int out;
Sint16 *to;
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to = inp - length;
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while( inp > to )
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out = 0;
out-= 9 * sum_d( inp, 16);
out+= 23 * sum_d( inp, 15);
out-= 46 * sum_d( inp, 14);
out+= 83 * sum_d( inp, 13);
out-= 138 * sum_d( inp, 12);
out+= 217 * sum_d( inp, 11);
out-= 326 * sum_d( inp, 10);
out+= 474 * sum_d( inp, 9);
out-= 671 * sum_d( inp, 8);
out+= 936 * sum_d( inp, 7);
out-= 1295 * sum_d( inp, 6);
out+= 1800 * sum_d( inp, 5);
out-= 2560 * sum_d( inp, 4);
out+= 3863 * sum_d( inp, 3);
out-= 6764 * sum_d( inp, 2);
out+= 20798 * sum_d( inp, 1);
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outp[CH(1)] = ( 32770 * inp[CH(1)] + out) >> 16;
outp[CH(0)] = ( 32770 * inp[CH(0)] + out) >> 16;
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inp -= CH(1);
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outp -= CH(2);
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return outp;
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}
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/*-------------------------------------------------------------------------*/
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#define sum_h(v,dx) ((int) v[CH(dx)] + v[CH(-dx)])
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static Sint16* Suffix(halfRate)( Sint16 *outp, Sint16 *inp, int length,
VarFilter* filt, int* cpos )
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{
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int out;
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Sint16* to;
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to = inp + length;
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while( inp < to )
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out = 0;
out-= 9 * sum_h( inp, 31);
out+= 23 * sum_h( inp, 29);
out-= 46 * sum_h( inp, 27);
out+= 83 * sum_h( inp, 25);
out-= 138 * sum_h( inp, 23);
out+= 217 * sum_h( inp, 21);
out-= 326 * sum_h( inp, 19);
out+= 474 * sum_h( inp, 17);
out-= 671 * sum_h( inp, 15);
out+= 936 * sum_h( inp, 13);
out-= 1295 * sum_h( inp, 11);
out+= 1800 * sum_h( inp, 9);
out-= 2560 * sum_h( inp, 7);
out+= 3863 * sum_h( inp, 5);
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out-= 6764 * sum_h( inp, 3);
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out+= 20798 * sum_h( inp, 1);
out+= 32770 * (int)inp[0];
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outp[0] = out >> 16;
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inp+= CH(2);
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outp += CH(1);
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}
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return outp;
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}
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/*-------------------------------------------------------------------------*/
static Sint16* Suffix(increaseRate)( Sint16 *outp, Sint16 *inp, int length,
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VarFilter* filter, int* cpos )
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{
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const static int fsize = CH(2*_fsize);
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Sint16 *f;
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int out;
int i, pos;
Sint16* to;
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inp -= fsize;
to = inp - length;
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pos = *cpos;
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while( inp > to )
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{
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out = 0;
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f = filter->c[pos];
for( i = _fsize + 1; --i; inp+=CH(4), f+=4 )
{
out+= f[0] * (int)inp[CH(0)];
out+= f[1] * (int)inp[CH(1)];
out+= f[2] * (int)inp[CH(2)];
out+= f[3] * (int)inp[CH(3)];
}
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outp[0] = out >> 16;
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pos = ( pos + filter->denominator - 1 ) % filter->denominator;
inp -= CH( 4 * _fsize );
inp -= CH( filter->incr[pos] );
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outp -= CH(1);
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}
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*cpos = pos;
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return outp;
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}
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/*-------------------------------------------------------------------------*/
static Sint16* Suffix(decreaseRate)( Sint16 *outp, Sint16 *inp, int length,
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VarFilter* filter, int* cpos )
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{
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const static int fsize = CH(2*_fsize);
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Sint16 *f;
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int out;
int i, pos;
Sint16 *to;
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inp -= fsize;
to = inp + length;
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pos = *cpos;
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while( inp < to )
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{
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out = 0;
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f = filter->c[pos];
for( i = _fsize + 1; --i; inp+=CH(4), f+=4 )
{
out+= f[0] * (int)inp[CH(0)];
out+= f[1] * (int)inp[CH(1)];
out+= f[2] * (int)inp[CH(2)];
out+= f[3] * (int)inp[CH(3)];
}
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outp[0] = out >> 16;
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inp -= CH( 4 * _fsize );
inp += CH( filter->incr[pos] );
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outp += CH(1);
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pos = ( pos + 1 ) % filter->denominator;
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}
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*cpos = pos;
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return outp;
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}
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/*-------------------------------------------------------------------------*/
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#undef sum_d
#undef sum_h
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#undef CH
#endif /* Suffix */