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

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

21 | 5ff85f1d | Michael Niedermayer | ```
/**
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22 | ```
* @file rational.c
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23 | ```
* Rational numbers
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24 | ```
* @author Michael Niedermayer <michaelni@gmx.at>
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25 | ```
*/
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26 | |||

27 | ```
//#include <math.h>
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28 | #include <limits.h> |
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29 | 115329f1 | Diego Biurrun | |

30 | 5ff85f1d | Michael Niedermayer | #include "common.h" |

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

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

33 | |||

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

35 | AVRational a0={0,1}, a1={1,0}; |
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36 | int sign= (nom<0) ^ (den<0); |
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37 | int64_t gcd= ff_gcd(ABS(nom), ABS(den)); |
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38 | |||

39 | nom = ABS(nom)/gcd; |
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40 | den = ABS(den)/gcd; |
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41 | ```
if(nom<=max && den<=max){
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42 | a1= (AVRational){nom, den}; |
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43 | ```
den=0;
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44 | } |
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45 | 115329f1 | Diego Biurrun | |

46 | c11c2bc2 | Alexander Strasser | ```
while(den){
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47 | int64_t x = nom / den; |
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48 | int64_t next_den= nom - den*x; |
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49 | int64_t a2n= x*a1.num + a0.num; |
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50 | int64_t a2d= x*a1.den + a0.den; |
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51 | |||

52 | if(a2n > max || a2d > max) break; |
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53 | |||

54 | a0= a1; |
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55 | a1= (AVRational){a2n, a2d}; |
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56 | nom= den; |
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57 | den= next_den; |
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58 | } |
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59 | ```
assert(ff_gcd(a1.num, a1.den) == 1);
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60 | 115329f1 | Diego Biurrun | |

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

62 | *dst_den = a1.den; |
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63 | 115329f1 | Diego Biurrun | |

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

65 | } |
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66 | |||

67 | 5c07b9e9 | Michael Niedermayer | ```
/**
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68 | ```
* returns b*c.
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69 | ```
*/
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70 | 5ff85f1d | Michael Niedermayer | AVRational av_mul_q(AVRational b, AVRational c){ |

71 | av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX); |
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72 | ```
return b;
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73 | } |
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74 | |||

75 | 5c07b9e9 | Michael Niedermayer | ```
/**
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76 | ```
* returns b/c.
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77 | ```
*/
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78 | 5ff85f1d | Michael Niedermayer | AVRational av_div_q(AVRational b, AVRational c){ |

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

83 | 5c07b9e9 | Michael Niedermayer | ```
/**
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84 | ```
* returns b+c.
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85 | ```
*/
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86 | 5ff85f1d | Michael Niedermayer | AVRational 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); |
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88 | ```
return b;
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89 | } |
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90 | |||

91 | 5c07b9e9 | Michael Niedermayer | ```
/**
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92 | ```
* returns b-c.
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93 | ```
*/
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94 | 5ff85f1d | Michael Niedermayer | AVRational av_sub_q(AVRational b, AVRational c){ |

95 | 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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96 | ```
return b;
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97 | } |
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98 | |||

99 | bf63eb4b | Michael Niedermayer | ```
/**
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100 | ```
* Converts a double precission floating point number to a AVRational.
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101 | ```
* @param max the maximum allowed numerator and denominator
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102 | ```
*/
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103 | 5ff85f1d | Michael Niedermayer | AVRational av_d2q(double d, int max){ |

104 | AVRational a; |
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105 | 33a6984b | Michael Niedermayer | int exponent= FFMAX( (int)(log(ABS(d) + 1e-20)/log(2)), 0); |

106 | 5ff85f1d | Michael Niedermayer | int64_t den= 1LL << (61 - exponent); |

107 | av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max); |
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108 | |||

109 | ```
return a;
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110 | } |