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 /**
22 * @file
23 * @addtogroup lavu_math
24 * Mathematical utilities for working with timestamp and time base.
25 */
26
27 #ifndef AVUTIL_MATHEMATICS_H
28 #define AVUTIL_MATHEMATICS_H
29
30 #include <stdint.h>
31 #include <math.h>
35
36 #ifndef M_E
37 #define M_E 2.7182818284590452354 /* e */
38 #endif
39 #ifndef M_LN2
40 #define M_LN2 0.69314718055994530942 /* log_e 2 */
41 #endif
42 #ifndef M_LN10
43 #define M_LN10 2.30258509299404568402 /* log_e 10 */
44 #endif
45 #ifndef M_LOG2_10
46 #define M_LOG2_10 3.32192809488736234787 /* log_2 10 */
47 #endif
48 #ifndef M_PHI
49 #define M_PHI 1.61803398874989484820 /* phi / golden ratio */
50 #endif
51 #ifndef M_PI
52 #define M_PI 3.14159265358979323846 /* pi */
53 #endif
54 #ifndef M_PI_2
55 #define M_PI_2 1.57079632679489661923 /* pi/2 */
56 #endif
57 #ifndef M_SQRT1_2
58 #define M_SQRT1_2 0.70710678118654752440 /* 1/sqrt(2) */
59 #endif
60 #ifndef M_SQRT2
61 #define M_SQRT2 1.41421356237309504880 /* sqrt(2) */
62 #endif
63 #ifndef NAN
64 #define NAN av_int2float(0x7fc00000)
65 #endif
66 #ifndef INFINITY
67 #define INFINITY av_int2float(0x7f800000)
68 #endif
69
70 /**
71 * @addtogroup lavu_math
72 *
73 * @{
74 */
75
76 /**
77 * Rounding methods.
78 */
85 /**
86 * Flag telling rescaling functions to pass `INT64_MIN`/`MAX` through
87 * unchanged, avoiding special cases for #AV_NOPTS_VALUE.
88 *
89 * Unlike other values of the enumeration AVRounding, this value is a
90 * bitmask that must be used in conjunction with another value of the
91 * enumeration through a bitwise OR, in order to set behavior for normal
92 * cases.
93 *
94 * @code{.c}
95 * av_rescale_rnd(3, 1, 2, AV_ROUND_UP | AV_ROUND_PASS_MINMAX);
96 * // Rescaling 3:
97 * // Calculating 3 * 1 / 2
98 * // 3 / 2 is rounded up to 2
99 * // => 2
100 *
101 * av_rescale_rnd(AV_NOPTS_VALUE, 1, 2, AV_ROUND_UP | AV_ROUND_PASS_MINMAX);
102 * // Rescaling AV_NOPTS_VALUE:
103 * // AV_NOPTS_VALUE == INT64_MIN
104 * // AV_NOPTS_VALUE is passed through
105 * // => AV_NOPTS_VALUE
106 * @endcode
107 */
109 };
110
111 /**
112 * Compute the greatest common divisor of two integer operands.
113 *
114 * @param a Operand
115 * @param b Operand
116 * @return GCD of a and b up to sign; if a >= 0 and b >= 0, return value is >= 0;
117 * if a == 0 and b == 0, returns 0.
118 */
120
121 /**
122 * Rescale a 64-bit integer with rounding to nearest.
123 *
124 * The operation is mathematically equivalent to `a * b / c`, but writing that
125 * directly can overflow.
126 *
127 * This function is equivalent to av_rescale_rnd() with #AV_ROUND_NEAR_INF.
128 *
129 * @see av_rescale_rnd(), av_rescale_q(), av_rescale_q_rnd()
130 */
132
133 /**
134 * Rescale a 64-bit integer with specified rounding.
135 *
136 * The operation is mathematically equivalent to `a * b / c`, but writing that
137 * directly can overflow, and does not support different rounding methods.
138 * If the result is not representable then INT64_MIN is returned.
139 *
140 * @see av_rescale(), av_rescale_q(), av_rescale_q_rnd()
141 */
143
144 /**
145 * Rescale a 64-bit integer by 2 rational numbers.
146 *
147 * The operation is mathematically equivalent to `a * bq / cq`.
148 *
149 * This function is equivalent to av_rescale_q_rnd() with #AV_ROUND_NEAR_INF.
150 *
151 * @see av_rescale(), av_rescale_rnd(), av_rescale_q_rnd()
152 */
154
155 /**
156 * Rescale a 64-bit integer by 2 rational numbers with specified rounding.
157 *
158 * The operation is mathematically equivalent to `a * bq / cq`.
159 *
160 * @see av_rescale(), av_rescale_rnd(), av_rescale_q()
161 */
164
165 /**
166 * Compare two timestamps each in its own time base.
167 *
168 * @return One of the following values:
169 * - -1 if `ts_a` is before `ts_b`
170 * - 1 if `ts_a` is after `ts_b`
171 * - 0 if they represent the same position
172 *
173 * @warning
174 * The result of the function is undefined if one of the timestamps is outside
175 * the `int64_t` range when represented in the other's timebase.
176 */
178
179 /**
180 * Compare the remainders of two integer operands divided by a common divisor.
181 *
182 * In other words, compare the least significant `log2(mod)` bits of integers
183 * `a` and `b`.
184 *
185 * @code{.c}
186 * av_compare_mod(0x11, 0x02, 0x10) < 0 // since 0x11 % 0x10 (0x1) < 0x02 % 0x10 (0x2)
187 * av_compare_mod(0x11, 0x02, 0x20) > 0 // since 0x11 % 0x20 (0x11) > 0x02 % 0x20 (0x02)
188 * @endcode
189 *
190 * @param a Operand
191 * @param b Operand
192 * @param mod Divisor; must be a power of 2
193 * @return
194 * - a negative value if `a % mod < b % mod`
195 * - a positive value if `a % mod > b % mod`
196 * - zero if `a % mod == b % mod`
197 */
199
200 /**
201 * Rescale a timestamp while preserving known durations.
202 *
203 * This function is designed to be called per audio packet to scale the input
204 * timestamp to a different time base. Compared to a simple av_rescale_q()
205 * call, this function is robust against possible inconsistent frame durations.
206 *
207 * The `last` parameter is a state variable that must be preserved for all
208 * subsequent calls for the same stream. For the first call, `*last` should be
209 * initialized to #AV_NOPTS_VALUE.
210 *
211 * @param[in] in_tb Input time base
212 * @param[in] in_ts Input timestamp
213 * @param[in] fs_tb Duration time base; typically this is finer-grained
214 * (greater) than `in_tb` and `out_tb`
215 * @param[in] duration Duration till the next call to this function (i.e.
216 * duration of the current packet/frame)
217 * @param[in,out] last Pointer to a timestamp expressed in terms of
218 * `fs_tb`, acting as a state variable
219 * @param[in] out_tb Output timebase
220 * @return Timestamp expressed in terms of `out_tb`
221 *
222 * @note In the context of this function, "duration" is in term of samples, not
223 * seconds.
224 */
226
227 /**
228 * Add a value to a timestamp.
229 *
230 * This function guarantees that when the same value is repeatly added that
231 * no accumulation of rounding errors occurs.
232 *
233 * @param[in] ts Input timestamp
234 * @param[in] ts_tb Input timestamp time base
235 * @param[in] inc Value to be added
236 * @param[in] inc_tb Time base of `inc`
237 */
239
240
241 /**
242 * @}
243 */
244
245 #endif /* AVUTIL_MATHEMATICS_H */