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[libav.git] / libavutil / rational.c
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1/*
2 * Rational numbers
3 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
4 *
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5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
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8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
b78e7197 10 * version 2.1 of the License, or (at your option) any later version.
5ff85f1d 11 *
b78e7197 12 * FFmpeg is distributed in the hope that it will be useful,
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13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
b78e7197 18 * License along with FFmpeg; if not, write to the Free Software
5509bffa 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
5ff85f1d 20 */
115329f1 21
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22/**
23 * @file rational.c
24 * Rational numbers
25 * @author Michael Niedermayer <michaelni@gmx.at>
26 */
27
28//#include <math.h>
29#include <limits.h>
115329f1 30
5ff85f1d 31#include "common.h"
c11c2bc2 32#include "mathematics.h"
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33#include "rational.h"
34
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35int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){
36 AVRational a0={0,1}, a1={1,0};
37 int sign= (nom<0) ^ (den<0);
c26abfa5 38 int64_t gcd= ff_gcd(FFABS(nom), FFABS(den));
c11c2bc2 39
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40 if(gcd){
41 nom = FFABS(nom)/gcd;
42 den = FFABS(den)/gcd;
43 }
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44 if(nom<=max && den<=max){
45 a1= (AVRational){nom, den};
46 den=0;
47 }
115329f1 48
c11c2bc2 49 while(den){
62b9fc15 50 uint64_t x = nom / den;
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51 int64_t next_den= nom - den*x;
52 int64_t a2n= x*a1.num + a0.num;
53 int64_t a2d= x*a1.den + a0.den;
54
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55 if(a2n > max || a2d > max){
56 if(a1.num) x= (max - a0.num) / a1.num;
57 if(a1.den) x= FFMIN(x, (max - a0.den) / a1.den);
58
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59 if (den*(2*x*a1.den + a0.den) > nom*a1.den)
60 a1 = (AVRational){x*a1.num + a0.num, x*a1.den + a0.den};
61 break;
62 }
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63
64 a0= a1;
65 a1= (AVRational){a2n, a2d};
66 nom= den;
67 den= next_den;
68 }
6880edab 69 assert(ff_gcd(a1.num, a1.den) <= 1U);
115329f1 70
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71 *dst_nom = sign ? -a1.num : a1.num;
72 *dst_den = a1.den;
115329f1 73
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74 return den==0;
75}
76
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77AVRational av_mul_q(AVRational b, AVRational c){
78 av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX);
79 return b;
80}
81
82AVRational av_div_q(AVRational b, AVRational c){
79dc59b7 83 return av_mul_q(b, (AVRational){c.den, c.num});
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84}
85
86AVRational av_add_q(AVRational b, AVRational c){
87 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);
88 return b;
89}
90
91AVRational av_sub_q(AVRational b, AVRational c){
79dc59b7 92 return av_add_q(b, (AVRational){-c.num, c.den});
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93}
94
95AVRational av_d2q(double d, int max){
96 AVRational a;
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97#define LOG2 0.69314718055994530941723212145817656807550013436025
98 int exponent= FFMAX( (int)(log(fabs(d) + 1e-20)/LOG2), 0);
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99 int64_t den= 1LL << (61 - exponent);
100 av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max);
101
102 return a;
103}