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git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@380 0778d3d1-df1d-0410-868b-ea421aaaa00d
95 lines
2.3 KiB
C
95 lines
2.3 KiB
C
/*
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* interpolation.h - fast implementations of several interpolation-algorithms
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*
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* Copyright (c) 2004-2005 Tobias Doerffel <tobydox/at/users.sourceforge.net>
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*
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* This file is part of Linux MultiMedia Studio - http://lmms.sourceforge.net
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program (see COPYING); if not, write to the
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* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301 USA.
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*
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*/
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#ifndef _INTERPOLATION_H
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#define _INTERPOLATION_H
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#ifndef __USE_XOPEN
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#define __USE_XOPEN
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#endif
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#include <math.h>
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#include "lmms_constants.h"
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inline float hermiteInterpolate( float x0, float x1, float x2, float x3,
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float frac_pos )
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{
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const float frsq = frac_pos*frac_pos;
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const float frsq2 = 2*frsq;
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return( ( (x2-x0) *0.5f ) * ( frac_pos * (frsq+1) -frsq2 ) +
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( frsq2*frac_pos - 3*frsq ) * ( x1-x2 ) +
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frsq2 * (frac_pos-1) * ( ( x3-x1 ) * 0.25f ) + x1 );
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/*
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const float frsq = frac_pos*frac_pos;
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//const float frsq2 = 2*frsq;
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frac_pos *= 0.5;
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const float frcu = frsq*frac_pos;
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return (
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(frcu - frsq + frac_pos) * ((x2 - x0)) +
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(4*frcu - 3*frsq) * (x1 - x2)
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//frsq*(2*frac_pos-3) * (x1 - x2)
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+ (frcu - 0.5*frsq)*((x3 - x1))
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+ x1
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);
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*/
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}
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inline float cubicInterpolate( float v0, float v1, float v2, float v3, float x )
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{
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float frsq = x*x;
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float frcu = frsq*v0;
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float t1 = v3 + 3*v1;
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return( v1 + 0.5f * frcu + x * ( v2 - frcu * ( 1.0f/6.0f ) -
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t1 * ( 1.0f/6.0f ) - v0 / 3.0f ) + frsq * x * ( t1 *
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( 1.0f/6.0f ) - 0.5f * v2 ) + frsq * ( 0.5f * v2 - v1 ) );
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}
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inline float cosinusInterpolate( float v0, float v1, float x )
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{
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float f = cosf( x * ( F_PI_2 ) );
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return( v0*f + v1*( 1.0f-f ) );
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}
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inline float linearInterpolate( float v0, float v1, float x )
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{
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return( v0*( 1.0f-x ) + v1*x );
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}
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#endif
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