## ffmpeg / libavutil / rational.c @ 674bd4f6

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1 | 5ff85f1d | Michael Niedermayer | ```
/*
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2 | 89c9ff50 | Diego Biurrun | ```
* rational numbers
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3 | 5ff85f1d | Michael Niedermayer | ```
* 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.
``` |

11 | 5ff85f1d | Michael Niedermayer | ```
*
``` |

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 | 115329f1 | Diego Biurrun | |

22 | 5ff85f1d | Michael Niedermayer | ```
/**
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23 | ```
* @file rational.c
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24 | 89c9ff50 | Diego Biurrun | ```
* rational numbers
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25 | 5ff85f1d | Michael Niedermayer | ```
* @author Michael Niedermayer <michaelni@gmx.at>
``` |

26 | ```
*/
``` |
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27 | |||

28 | dfcb6b56 | Diego Biurrun | #include <assert.h> |

29 | 5ff85f1d | Michael Niedermayer | ```
//#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 | 674bd4f6 | Diego Biurrun | int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max){ |

37 | c11c2bc2 | Alexander Strasser | AVRational a0={0,1}, a1={1,0}; |

38 | 674bd4f6 | Diego Biurrun | int sign= (num<0) ^ (den<0); |

39 | int64_t gcd= av_gcd(FFABS(num), FFABS(den)); |
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40 | c11c2bc2 | Alexander Strasser | |

41 | 6880edab | Michael Niedermayer | ```
if(gcd){
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42 | 674bd4f6 | Diego Biurrun | num = FFABS(num)/gcd; |

43 | 6880edab | Michael Niedermayer | den = FFABS(den)/gcd; |

44 | } |
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45 | 674bd4f6 | Diego Biurrun | ```
if(num<=max && den<=max){
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46 | a1= (AVRational){num, den}; |
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47 | c11c2bc2 | Alexander Strasser | ```
den=0;
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48 | } |
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49 | 115329f1 | Diego Biurrun | |

50 | c11c2bc2 | Alexander Strasser | ```
while(den){
``` |

51 | 674bd4f6 | Diego Biurrun | uint64_t x = num / den; |

52 | int64_t next_den= num - den*x; |
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53 | c11c2bc2 | Alexander Strasser | int64_t a2n= x*a1.num + a0.num; |

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 | 674bd4f6 | Diego Biurrun | if (den*(2*x*a1.den + a0.den) > num*a1.den) |

61 | 3db1b8b5 | Michael Niedermayer | a1 = (AVRational){x*a1.num + a0.num, x*a1.den + a0.den}; |

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 | 674bd4f6 | Diego Biurrun | num= den; |

68 | c11c2bc2 | Alexander Strasser | den= next_den; |

69 | } |
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70 | 9ce6c138 | Aurelien Jacobs | ```
assert(av_gcd(a1.num, a1.den) <= 1U);
``` |

71 | 115329f1 | Diego Biurrun | |

72 | 674bd4f6 | Diego Biurrun | *dst_num = sign ? -a1.num : a1.num; |

73 | c11c2bc2 | Alexander Strasser | *dst_den = a1.den; |

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});
``` |

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 | } |
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105 | 05b90fc0 | Stefano Sabatini | |

106 | ```
int av_nearer_q(AVRational q, AVRational q1, AVRational q2)
``` |
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107 | { |
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108 | ```
/* n/d is q, a/b is the median between q1 and q2 */
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109 | int64_t a = q1.num * (int64_t)q2.den + q2.num * (int64_t)q1.den; |
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110 | ```
int64_t b = 2 * (int64_t)q1.den * q2.den;
``` |
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111 | |||

112 | ```
/* rnd_up(a*d/b) > n => a*d/b > n */
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113 | int64_t x_up = av_rescale_rnd(a, q.den, b, AV_ROUND_UP); |
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114 | |||

115 | ```
/* rnd_down(a*d/b) < n => a*d/b < n */
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116 | int64_t x_down = av_rescale_rnd(a, q.den, b, AV_ROUND_DOWN); |
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117 | |||

118 | ```
return ((x_up > q.num) - (x_down < q.num)) * av_cmp_q(q2, q1);
``` |
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119 | } |
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120 | |||

121 | int av_find_nearest_q_idx(AVRational q, const AVRational* q_list) |
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122 | { |
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123 | int i, nearest_q_idx = 0; |
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124 | for(i=0; q_list[i].den; i++) |
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125 | if (av_nearer_q(q, q_list[i], q_list[nearest_q_idx]) > 0) |
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126 | nearest_q_idx = i; |
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127 | |||

128 | ```
return nearest_q_idx;
``` |
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129 | } |