ffmpeg / libavutil / rational.c @ 5509bffa
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/*


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* Rational numbers

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* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>

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*

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* This library is free software; you can redistribute it and/or

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* modify it under the terms of the GNU Lesser 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 library 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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* Lesser General Public License for more details.

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*

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* You should have received a copy of the GNU Lesser General Public

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* License along with this library; if not, write to the Free Software

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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 USA

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*

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*/

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/**

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* @file rational.c

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* Rational numbers

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* @author Michael Niedermayer <michaelni@gmx.at>

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*/

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//#include <math.h>

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#include <limits.h> 
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#include "common.h" 
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#include "mathematics.h" 
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#include "rational.h" 
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int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){ 
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AVRational a0={0,1}, a1={1,0}; 
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int sign= (nom<0) ^ (den<0); 
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int64_t gcd= ff_gcd(ABS(nom), ABS(den)); 
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nom = ABS(nom)/gcd; 
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den = ABS(den)/gcd; 
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if(nom<=max && den<=max){

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a1= (AVRational){nom, den}; 
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den=0;

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} 
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while(den){

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int64_t x = nom / den; 
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int64_t next_den= nom  den*x; 
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int64_t a2n= x*a1.num + a0.num; 
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int64_t a2d= x*a1.den + a0.den; 
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if(a2n > max  a2d > max) break; 
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a0= a1; 
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a1= (AVRational){a2n, a2d}; 
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nom= den; 
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den= next_den; 
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} 
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assert(ff_gcd(a1.num, a1.den) == 1);

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*dst_nom = sign ? a1.num : a1.num; 
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*dst_den = a1.den; 
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return den==0; 
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} 
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/**

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* returns b*c.

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*/

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AVRational av_mul_q(AVRational b, AVRational c){ 
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX); 
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return b;

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} 
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/**

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* returns b/c.

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*/

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AVRational av_div_q(AVRational b, AVRational c){ 
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.den, b.den * (int64_t)c.num, INT_MAX); 
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return b;

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} 
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/**

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* returns b+c.

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*/

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AVRational av_add_q(AVRational b, AVRational c){ 
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.den + c.num * (int64_t)b.den, b.den * (int64_t)c.den, INT_MAX); 
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return b;

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} 
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/**

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* returns bc.

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*/

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AVRational av_sub_q(AVRational b, AVRational c){ 
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av_reduce(&b.num, &b.den, b.num * (int64_t)c.den  c.num * (int64_t)b.den, b.den * (int64_t)c.den, INT_MAX); 
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return b;

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} 
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/**

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* Converts a double precission floating point number to a AVRational.

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* @param max the maximum allowed numerator and denominator

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*/

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AVRational av_d2q(double d, int max){ 
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AVRational a; 
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int exponent= FFMAX( (int)(log(ABS(d) + 1e20)/log(2)), 0); 
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int64_t den= 1LL << (61  exponent); 
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av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max); 
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return a;

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} 