FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
mathematics.h
Go to the documentation of this file.
1 /*
2  * copyright (c) 2005-2012 Michael Niedermayer <michaelni@gmx.at>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #ifndef AVUTIL_MATHEMATICS_H
22 #define AVUTIL_MATHEMATICS_H
23 
24 #include <stdint.h>
25 #include <math.h>
26 #include "attributes.h"
27 #include "rational.h"
28 #include "intfloat.h"
29 
30 #ifndef M_E
31 #define M_E 2.7182818284590452354 /* e */
32 #endif
33 #ifndef M_LN2
34 #define M_LN2 0.69314718055994530942 /* log_e 2 */
35 #endif
36 #ifndef M_LN10
37 #define M_LN10 2.30258509299404568402 /* log_e 10 */
38 #endif
39 #ifndef M_LOG2_10
40 #define M_LOG2_10 3.32192809488736234787 /* log_2 10 */
41 #endif
42 #ifndef M_PHI
43 #define M_PHI 1.61803398874989484820 /* phi / golden ratio */
44 #endif
45 #ifndef M_PI
46 #define M_PI 3.14159265358979323846 /* pi */
47 #endif
48 #ifndef M_SQRT1_2
49 #define M_SQRT1_2 0.70710678118654752440 /* 1/sqrt(2) */
50 #endif
51 #ifndef M_SQRT2
52 #define M_SQRT2 1.41421356237309504880 /* sqrt(2) */
53 #endif
54 #ifndef NAN
55 #define NAN av_int2float(0x7fc00000)
56 #endif
57 #ifndef INFINITY
58 #define INFINITY av_int2float(0x7f800000)
59 #endif
60 
61 /**
62  * @addtogroup lavu_math
63  * @{
64  */
65 
66 
67 enum AVRounding {
68  AV_ROUND_ZERO = 0, ///< Round toward zero.
69  AV_ROUND_INF = 1, ///< Round away from zero.
70  AV_ROUND_DOWN = 2, ///< Round toward -infinity.
71  AV_ROUND_UP = 3, ///< Round toward +infinity.
72  AV_ROUND_NEAR_INF = 5, ///< Round to nearest and halfway cases away from zero.
73  AV_ROUND_PASS_MINMAX = 8192, ///< Flag to pass INT64_MIN/MAX through instead of rescaling, this avoids special cases for AV_NOPTS_VALUE
74 };
75 
76 /**
77  * Return the greatest common divisor of a and b.
78  * If both a and b are 0 or either or both are <0 then behavior is
79  * undefined.
80  */
81 int64_t av_const av_gcd(int64_t a, int64_t b);
82 
83 /**
84  * Rescale a 64-bit integer with rounding to nearest.
85  * A simple a*b/c isn't possible as it can overflow.
86  */
87 int64_t av_rescale(int64_t a, int64_t b, int64_t c) av_const;
88 
89 /**
90  * Rescale a 64-bit integer with specified rounding.
91  * A simple a*b/c isn't possible as it can overflow.
92  *
93  * @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is
94  * INT64_MIN or INT64_MAX then a is passed through unchanged.
95  */
96 int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding) av_const;
97 
98 /**
99  * Rescale a 64-bit integer by 2 rational numbers.
100  */
101 int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
102 
103 /**
104  * Rescale a 64-bit integer by 2 rational numbers with specified rounding.
105  *
106  * @return rescaled value a, or if AV_ROUND_PASS_MINMAX is set and a is
107  * INT64_MIN or INT64_MAX then a is passed through unchanged.
108  */
109 int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq,
110  enum AVRounding) av_const;
111 
112 /**
113  * Compare 2 timestamps each in its own timebases.
114  * The result of the function is undefined if one of the timestamps
115  * is outside the int64_t range when represented in the others timebase.
116  * @return -1 if ts_a is before ts_b, 1 if ts_a is after ts_b or 0 if they represent the same position
117  */
118 int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b);
119 
120 /**
121  * Compare 2 integers modulo mod.
122  * That is we compare integers a and b for which only the least
123  * significant log2(mod) bits are known.
124  *
125  * @param mod must be a power of 2
126  * @return a negative value if a is smaller than b
127  * a positive value if a is greater than b
128  * 0 if a equals b
129  */
130 int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod);
131 
132 /**
133  * Rescale a timestamp while preserving known durations.
134  *
135  * @param in_ts Input timestamp
136  * @param in_tb Input timesbase
137  * @param fs_tb Duration and *last timebase
138  * @param duration duration till the next call
139  * @param out_tb Output timesbase
140  */
141 int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb);
142 
143 /**
144  * @}
145  */
146 
147 #endif /* AVUTIL_MATHEMATICS_H */