rational.h 3.7 KB

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  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. * @file
  23. * rational numbers
  24. * @author Michael Niedermayer <michaelni@gmx.at>
  25. */
  26. #ifndef AVUTIL_RATIONAL_H
  27. #define AVUTIL_RATIONAL_H
  28. #include <stdint.h>
  29. #include <limits.h>
  30. #include "attributes.h"
  31. /**
  32. * @addtogroup lavu_math
  33. * @{
  34. */
  35. /**
  36. * rational number numerator/denominator
  37. */
  38. typedef struct AVRational{
  39. int num; ///< numerator
  40. int den; ///< denominator
  41. } AVRational;
  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, -1 if a<b, and INT_MIN if one of the
  47. * values is of the form 0/0
  48. */
  49. static inline int av_cmp_q(AVRational a, AVRational b){
  50. const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
  51. if(tmp) return ((tmp ^ a.den ^ b.den)>>63)|1;
  52. else if(b.den && a.den) return 0;
  53. else if(a.num && b.num) return (a.num>>31) - (b.num>>31);
  54. else return INT_MIN;
  55. }
  56. /**
  57. * Convert rational to double.
  58. * @param a rational to convert
  59. * @return (double) a
  60. */
  61. static inline double av_q2d(AVRational a){
  62. return a.num / (double) a.den;
  63. }
  64. /**
  65. * Reduce a fraction.
  66. * This is useful for framerate calculations.
  67. * @param dst_num destination numerator
  68. * @param dst_den destination denominator
  69. * @param num source numerator
  70. * @param den source denominator
  71. * @param max the maximum allowed for dst_num & dst_den
  72. * @return 1 if exact, 0 otherwise
  73. */
  74. int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max);
  75. /**
  76. * Multiply two rationals.
  77. * @param b first rational
  78. * @param c second rational
  79. * @return b*c
  80. */
  81. AVRational av_mul_q(AVRational b, AVRational c) av_const;
  82. /**
  83. * Divide one rational by another.
  84. * @param b first rational
  85. * @param c second rational
  86. * @return b/c
  87. */
  88. AVRational av_div_q(AVRational b, AVRational c) av_const;
  89. /**
  90. * Add two rationals.
  91. * @param b first rational
  92. * @param c second rational
  93. * @return b+c
  94. */
  95. AVRational av_add_q(AVRational b, AVRational c) av_const;
  96. /**
  97. * Subtract one rational from another.
  98. * @param b first rational
  99. * @param c second rational
  100. * @return b-c
  101. */
  102. AVRational av_sub_q(AVRational b, AVRational c) av_const;
  103. /**
  104. * Convert a double precision floating point number to a rational.
  105. * inf is expressed as {1,0} or {-1,0} depending on the sign.
  106. *
  107. * @param d double to convert
  108. * @param max the maximum allowed numerator and denominator
  109. * @return (AVRational) d
  110. */
  111. AVRational av_d2q(double d, int max) av_const;
  112. /**
  113. * @return 1 if q1 is nearer to q than q2, -1 if q2 is nearer
  114. * than q1, 0 if they have the same distance.
  115. */
  116. int av_nearer_q(AVRational q, AVRational q1, AVRational q2);
  117. /**
  118. * Find the nearest value in q_list to q.
  119. * @param q_list an array of rationals terminated by {0, 0}
  120. * @return the index of the nearest value found in the array
  121. */
  122. int av_find_nearest_q_idx(AVRational q, const AVRational* q_list);
  123. /**
  124. * @}
  125. */
  126. #endif /* AVUTIL_RATIONAL_H */