## ffmpeg / libavutil / rational.c @ 699b3f99

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1 | 5ff85f1d | Michael Niedermayer | ```
/*
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2 | ```
* Rational numbers
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3 | ```
* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
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4 | ```
*
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5 | b78e7197 | Diego Biurrun | ```
* This file is part of FFmpeg.
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6 | ```
*
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7 | ```
* FFmpeg is free software; you can redistribute it and/or
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8 | 5ff85f1d | Michael Niedermayer | ```
* modify it under the terms of the GNU Lesser General Public
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9 | ```
* License as published by the Free Software Foundation; either
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10 | b78e7197 | Diego Biurrun | ```
* version 2.1 of the License, or (at your option) any later version.
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11 | 5ff85f1d | Michael Niedermayer | ```
*
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12 | b78e7197 | Diego Biurrun | ```
* FFmpeg is distributed in the hope that it will be useful,
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13 | 5ff85f1d | Michael Niedermayer | ```
* but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | ```
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 | ```
* Lesser General Public License for more details.
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16 | ```
*
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17 | ```
* You should have received a copy of the GNU Lesser General Public
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18 | b78e7197 | Diego Biurrun | ```
* License along with FFmpeg; if not, write to the Free Software
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19 | 5509bffa | Diego Biurrun | ```
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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20 | 5ff85f1d | Michael Niedermayer | ```
*
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21 | ```
*/
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22 | 115329f1 | Diego Biurrun | |

23 | 5ff85f1d | Michael Niedermayer | ```
/**
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24 | ```
* @file rational.c
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25 | ```
* Rational numbers
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26 | ```
* @author Michael Niedermayer <michaelni@gmx.at>
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27 | ```
*/
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28 | |||

29 | ```
//#include <math.h>
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30 | #include <limits.h> |
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31 | 115329f1 | Diego Biurrun | |

32 | 5ff85f1d | Michael Niedermayer | #include "common.h" |

33 | c11c2bc2 | Alexander Strasser | #include "mathematics.h" |

34 | 5ff85f1d | Michael Niedermayer | #include "rational.h" |

35 | |||

36 | c11c2bc2 | Alexander Strasser | int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){ |

37 | AVRational a0={0,1}, a1={1,0}; |
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38 | int sign= (nom<0) ^ (den<0); |
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39 | c26abfa5 | Diego Biurrun | int64_t gcd= ff_gcd(FFABS(nom), FFABS(den)); |

40 | c11c2bc2 | Alexander Strasser | |

41 | 6880edab | Michael Niedermayer | ```
if(gcd){
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42 | nom = FFABS(nom)/gcd; |
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43 | den = FFABS(den)/gcd; |
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44 | } |
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45 | c11c2bc2 | Alexander Strasser | ```
if(nom<=max && den<=max){
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46 | a1= (AVRational){nom, den}; |
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47 | ```
den=0;
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48 | } |
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49 | 115329f1 | Diego Biurrun | |

50 | c11c2bc2 | Alexander Strasser | ```
while(den){
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51 | 62b9fc15 | Michael Niedermayer | uint64_t x = nom / den; |

52 | c11c2bc2 | Alexander Strasser | int64_t next_den= nom - den*x; |

53 | int64_t a2n= x*a1.num + a0.num; |
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54 | int64_t a2d= x*a1.den + a0.den; |
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55 | |||

56 | 3db1b8b5 | Michael Niedermayer | ```
if(a2n > max || a2d > max){
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57 | ```
if(a1.num) x= (max - a0.num) / a1.num;
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58 | ```
if(a1.den) x= FFMIN(x, (max - a0.den) / a1.den);
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59 | |||

60 | if (den*(2*x*a1.den + a0.den) > nom*a1.den) |
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61 | a1 = (AVRational){x*a1.num + a0.num, x*a1.den + a0.den}; |
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62 | ```
break;
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63 | } |
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64 | c11c2bc2 | Alexander Strasser | |

65 | a0= a1; |
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66 | a1= (AVRational){a2n, a2d}; |
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67 | nom= den; |
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68 | den= next_den; |
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69 | } |
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70 | 6880edab | Michael Niedermayer | ```
assert(ff_gcd(a1.num, a1.den) <= 1U);
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71 | 115329f1 | Diego Biurrun | |

72 | c11c2bc2 | Alexander Strasser | *dst_nom = sign ? -a1.num : a1.num; |

73 | *dst_den = a1.den; |
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74 | 115329f1 | Diego Biurrun | |

75 | c11c2bc2 | Alexander Strasser | return den==0; |

76 | } |
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77 | |||

78 | 5ff85f1d | Michael Niedermayer | AVRational av_mul_q(AVRational b, AVRational c){ |

79 | av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX); |
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80 | ```
return b;
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81 | } |
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82 | |||

83 | AVRational av_div_q(AVRational b, AVRational c){ |
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84 | 79dc59b7 | Michael Niedermayer | ```
return av_mul_q(b, (AVRational){c.den, c.num});
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85 | 5ff85f1d | Michael Niedermayer | } |

86 | |||

87 | AVRational av_add_q(AVRational b, AVRational c){ |
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88 | 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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89 | ```
return b;
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90 | } |
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91 | |||

92 | AVRational av_sub_q(AVRational b, AVRational c){ |
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93 | 79dc59b7 | Michael Niedermayer | ```
return av_add_q(b, (AVRational){-c.num, c.den});
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94 | 5ff85f1d | Michael Niedermayer | } |

95 | |||

96 | AVRational av_d2q(double d, int max){ |
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97 | AVRational a; |
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98 | 79dc59b7 | Michael Niedermayer | #define LOG2 0.69314718055994530941723212145817656807550013436025 |

99 | int exponent= FFMAX( (int)(log(fabs(d) + 1e-20)/LOG2), 0); |
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100 | 5ff85f1d | Michael Niedermayer | int64_t den= 1LL << (61 - exponent); |

101 | av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max); |
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102 | |||

103 | ```
return a;
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104 | } |