libavutil/rational.h

   1 /*
   2  * Rational numbers
   3  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  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
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file rational.h
  24  * Rational numbers.
  25  * @author Michael Niedermayer <michaelni@gmx.at>
  26  */
  27
  28 #ifndef FFMPEG_RATIONAL_H
  29 #define FFMPEG_RATIONAL_H
  30
  31 #include <stdint.h>
  32 #include "common.h"
  33
  34 /**
  35  * Rational number num/den.
  36  */
  37 typedef struct AVRational{
  38     int num; ///< numerator
  39     int den; ///< denominator
  40 } AVRational;
  41
  42 /**
  43  * Compare two rationals.
  44  * @param a first rational
  45  * @param b second rational
  46  * @return 0 if a==b, 1 if a>b and -1 if a<b.
  47  */
  48 static inline int av_cmp_q(AVRational a, AVRational b){
  49     const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
  50
  51     if(tmp) return (tmp>>63)|1;
  52     else    return 0;
  53 }
  54
  55 /**
  56  * Rational to double conversion.
  57  * @param a rational to convert
  58  * @return (double) a
  59  */
  60 static inline double av_q2d(AVRational a){
  61     return a.num / (double) a.den;
  62 }
  63
  64 /**
  65  * Reduce a fraction.
  66  * This is useful for framerate calculations.
  67  * @param dst_nom destination numerator
  68  * @param dst_den destination denominator
  69  * @param nom source numerator
  70  * @param den source denominator
  71  * @param max the maximum allowed for dst_nom & dst_den
  72  * @return 1 if exact, 0 otherwise
  73  */
  74 int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max);
  75
  76 /**
  77  * Multiplies two rationals.
  78  * @param b first rational.
  79  * @param c second rational.
  80  * @return b*c.
  81  */
  82 AVRational av_mul_q(AVRational b, AVRational c) av_const;
  83
  84 /**
  85  * Divides one rational by another.
  86  * @param b first rational.
  87  * @param c second rational.
  88  * @return b/c.
  89  */
  90 AVRational av_div_q(AVRational b, AVRational c) av_const;
  91
  92 /**
  93  * Adds two rationals.
  94  * @param b first rational.
  95  * @param c second rational.
  96  * @return b+c.
  97  */
  98 AVRational av_add_q(AVRational b, AVRational c) av_const;
  99
 100 /**
 101  * Subtracts one rational from another.
 102  * @param b first rational.
 103  * @param c second rational.
 104  * @return b-c.
 105  */
 106 AVRational av_sub_q(AVRational b, AVRational c) av_const;
 107
 108 /**
 109  * Converts a double precision floating point number to a rational.
 110  * @param d double to convert
 111  * @param max the maximum allowed numerator and denominator
 112  * @return (AVRational) d.
 113  */
 114 AVRational av_d2q(double d, int max) av_const;
 115
 116 #endif /* FFMPEG_RATIONAL_H */