FFmpeg
mathematics.c
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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  * miscellaneous math routines and tables
24  */
25 
26 #include <stdint.h>
27 #include <limits.h>
28 
29 #include "mathematics.h"
30 #include "libavutil/intmath.h"
31 #include "libavutil/common.h"
32 #include "avassert.h"
33 #include "version.h"
34 
35 /* Stein's binary GCD algorithm:
36  * https://en.wikipedia.org/wiki/Binary_GCD_algorithm */
37 int64_t av_gcd(int64_t a, int64_t b) {
38  int za, zb, k;
39  int64_t u, v;
40  if (a == 0)
41  return b;
42  if (b == 0)
43  return a;
44  za = ff_ctzll(a);
45  zb = ff_ctzll(b);
46  k = FFMIN(za, zb);
47  u = llabs(a >> za);
48  v = llabs(b >> zb);
49  while (u != v) {
50  if (u > v)
51  FFSWAP(int64_t, v, u);
52  v -= u;
53  v >>= ff_ctzll(v);
54  }
55  return (uint64_t)u << k;
56 }
57 
58 int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd)
59 {
60  int64_t r = 0;
61  av_assert2(c > 0);
62  av_assert2(b >=0);
63  av_assert2((unsigned)(rnd&~AV_ROUND_PASS_MINMAX)<=5 && (rnd&~AV_ROUND_PASS_MINMAX)!=4);
64 
65  if (c <= 0 || b < 0 || !((unsigned)(rnd&~AV_ROUND_PASS_MINMAX)<=5 && (rnd&~AV_ROUND_PASS_MINMAX)!=4))
66  return INT64_MIN;
67 
68  if (rnd & AV_ROUND_PASS_MINMAX) {
69  if (a == INT64_MIN || a == INT64_MAX)
70  return a;
71  rnd -= AV_ROUND_PASS_MINMAX;
72  }
73 
74  if (a < 0)
75  return -(uint64_t)av_rescale_rnd(-FFMAX(a, -INT64_MAX), b, c, rnd ^ ((rnd >> 1) & 1));
76 
77  if (rnd == AV_ROUND_NEAR_INF)
78  r = c / 2;
79  else if (rnd & 1)
80  r = c - 1;
81 
82  if (b <= INT_MAX && c <= INT_MAX) {
83  if (a <= INT_MAX)
84  return (a * b + r) / c;
85  else {
86  int64_t ad = a / c;
87  int64_t a2 = (a % c * b + r) / c;
88  if (ad >= INT32_MAX && b && ad > (INT64_MAX - a2) / b)
89  return INT64_MIN;
90  return ad * b + a2;
91  }
92  } else {
93 #if 1
94  uint64_t a0 = a & 0xFFFFFFFF;
95  uint64_t a1 = a >> 32;
96  uint64_t b0 = b & 0xFFFFFFFF;
97  uint64_t b1 = b >> 32;
98  uint64_t t1 = a0 * b1 + a1 * b0;
99  uint64_t t1a = t1 << 32;
100  int i;
101 
102  a0 = a0 * b0 + t1a;
103  a1 = a1 * b1 + (t1 >> 32) + (a0 < t1a);
104  a0 += r;
105  a1 += a0 < r;
106 
107  for (i = 63; i >= 0; i--) {
108  a1 += a1 + ((a0 >> i) & 1);
109  t1 += t1;
110  if (c <= a1) {
111  a1 -= c;
112  t1++;
113  }
114  }
115  if (t1 > INT64_MAX)
116  return INT64_MIN;
117  return t1;
118 #else
119  /* reference code doing (a*b + r) / c, requires libavutil/integer.h */
120  AVInteger ai;
121  ai = av_mul_i(av_int2i(a), av_int2i(b));
122  ai = av_add_i(ai, av_int2i(r));
123 
124  return av_i2int(av_div_i(ai, av_int2i(c)));
125 #endif
126  }
127 }
128 
129 int64_t av_rescale(int64_t a, int64_t b, int64_t c)
130 {
131  return av_rescale_rnd(a, b, c, AV_ROUND_NEAR_INF);
132 }
133 
134 int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq,
135  enum AVRounding rnd)
136 {
137  int64_t b = bq.num * (int64_t)cq.den;
138  int64_t c = cq.num * (int64_t)bq.den;
139  return av_rescale_rnd(a, b, c, rnd);
140 }
141 
142 int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
143 {
144  return av_rescale_q_rnd(a, bq, cq, AV_ROUND_NEAR_INF);
145 }
146 
147 int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b)
148 {
149  int64_t a = tb_a.num * (int64_t)tb_b.den;
150  int64_t b = tb_b.num * (int64_t)tb_a.den;
151  if ((FFABS(ts_a)|a|FFABS(ts_b)|b) <= INT_MAX)
152  return (ts_a*a > ts_b*b) - (ts_a*a < ts_b*b);
153  if (av_rescale_rnd(ts_a, a, b, AV_ROUND_DOWN) < ts_b)
154  return -1;
155  if (av_rescale_rnd(ts_b, b, a, AV_ROUND_DOWN) < ts_a)
156  return 1;
157  return 0;
158 }
159 
160 int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod)
161 {
162  int64_t c = (a - b) & (mod - 1);
163  if (c > (mod >> 1))
164  c -= mod;
165  return c;
166 }
167 
168 int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb){
169  int64_t a, b, this;
170 
171  av_assert0(in_ts != AV_NOPTS_VALUE);
172  av_assert0(duration >= 0);
173 
174  if (*last == AV_NOPTS_VALUE || !duration || in_tb.num*(int64_t)out_tb.den <= out_tb.num*(int64_t)in_tb.den) {
175 simple_round:
176  *last = av_rescale_q(in_ts, in_tb, fs_tb) + duration;
177  return av_rescale_q(in_ts, in_tb, out_tb);
178  }
179 
180  a = av_rescale_q_rnd(2*in_ts-1, in_tb, fs_tb, AV_ROUND_DOWN) >>1;
181  b = (av_rescale_q_rnd(2*in_ts+1, in_tb, fs_tb, AV_ROUND_UP )+1)>>1;
182  if (*last < 2*a - b || *last > 2*b - a)
183  goto simple_round;
184 
185  this = av_clip64(*last, a, b);
186  *last = this + duration;
187 
188  return av_rescale_q(this, fs_tb, out_tb);
189 }
190 
191 int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc)
192 {
193  int64_t m, d;
194 
195  if (inc != 1)
196  inc_tb = av_mul_q(inc_tb, (AVRational) {inc, 1});
197 
198  m = inc_tb.num * (int64_t)ts_tb.den;
199  d = inc_tb.den * (int64_t)ts_tb.num;
200 
201  if (m % d == 0 && ts <= INT64_MAX - m / d)
202  return ts + m / d;
203  if (m < d)
204  return ts;
205 
206  {
207  int64_t old = av_rescale_q(ts, ts_tb, inc_tb);
208  int64_t old_ts = av_rescale_q(old, inc_tb, ts_tb);
209 
210  if (old == INT64_MAX)
211  return ts;
212 
213  return av_rescale_q(old + 1, inc_tb, ts_tb) + (ts - old_ts);
214  }
215 }
#define a0
Definition: regdef.h:46
int num
Numerator.
Definition: rational.h:59
The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a
Definition: undefined.txt:36
#define a1
Definition: regdef.h:47
AVRounding
Rounding methods.
Definition: mathematics.h:79
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
Round toward +infinity.
Definition: mathematics.h:83
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:64
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
#define u(width, name, range_min, range_max)
Definition: cbs_h2645.c:252
int64_t duration
Definition: movenc.c:63
int64_t av_i2int(AVInteger a)
Convert the given AVInteger to an int64_t.
Definition: integer.c:158
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
Rescale a 64-bit integer by 2 rational numbers.
Definition: mathematics.c:142
AVInteger av_int2i(int64_t a)
Convert the given int64_t to an AVInteger.
Definition: integer.c:147
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
const char * r
Definition: vf_curves.c:114
#define t1
Definition: regdef.h:29
Round to nearest and halfway cases away from zero.
Definition: mathematics.h:84
AVInteger av_mul_i(AVInteger a, AVInteger b)
Definition: integer.c:64
simple assert() macros that are a bit more flexible than ISO C assert().
int64_t av_gcd(int64_t a, int64_t b)
Compute the greatest common divisor of two integer operands.
Definition: mathematics.c:37
Libavutil version macros.
#define FFMAX(a, b)
Definition: common.h:94
int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b)
Compare two timestamps each in its own time base.
Definition: mathematics.c:147
#define b
Definition: input.c:41
int64_t av_rescale(int64_t a, int64_t b, int64_t c)
Rescale a 64-bit integer with rounding to nearest.
Definition: mathematics.c:129
#define FFMIN(a, b)
Definition: common.h:96
#define ff_ctzll
Definition: intmath.h:126
#define a2
Definition: regdef.h:48
AVInteger av_add_i(AVInteger a, AVInteger b)
Definition: integer.c:34
#define FFABS(a)
Absolute value, Note, INT_MIN / INT64_MIN result in undefined behavior as they are not representable ...
Definition: common.h:72
int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd)
Rescale a 64-bit integer with specified rounding.
Definition: mathematics.c:58
int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb)
Rescale a timestamp while preserving known durations.
Definition: mathematics.c:168
static int mod(int a, int b)
Modulo operation with only positive remainders.
Definition: vf_v360.c:470
Rational number (pair of numerator and denominator).
Definition: rational.h:58
Round toward -infinity.
Definition: mathematics.h:82
common internal and external API header
int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc)
Add a value to a timestamp.
Definition: mathematics.c:191
#define rnd()
Definition: checkasm.h:105
AVInteger av_div_i(AVInteger a, AVInteger b)
Return a/b.
Definition: integer.c:141
int den
Denominator.
Definition: rational.h:60
Flag telling rescaling functions to pass INT64_MIN/MAX through unchanged, avoiding special cases for ...
Definition: mathematics.h:108
AVRational av_mul_q(AVRational b, AVRational c)
Multiply two rationals.
Definition: rational.c:80
int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq, enum AVRounding rnd)
Rescale a 64-bit integer by 2 rational numbers with specified rounding.
Definition: mathematics.c:134
#define FFSWAP(type, a, b)
Definition: common.h:99
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod)
Compare the remainders of two integer operands divided by a common divisor.
Definition: mathematics.c:160