FFmpeg
celp_math.c
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1 /*
2  * Various fixed-point math operations
3  *
4  * Copyright (c) 2008 Vladimir Voroshilov
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #include <inttypes.h>
24 #include <limits.h>
25 
26 #include "libavutil/avassert.h"
27 #include "avcodec.h"
28 #include "mathops.h"
29 #include "celp_math.h"
30 #include "libavutil/common.h"
31 
32 #ifdef G729_BITEXACT
33 static const uint16_t exp2a[]=
34 {
35  0, 1435, 2901, 4400, 5931, 7496, 9096, 10730,
36  12400, 14106, 15850, 17632, 19454, 21315, 23216, 25160,
37  27146, 29175, 31249, 33368, 35534, 37747, 40009, 42320,
38  44682, 47095, 49562, 52082, 54657, 57289, 59979, 62727,
39 };
40 
41 static const uint16_t exp2b[]=
42 {
43  3, 712, 1424, 2134, 2845, 3557, 4270, 4982,
44  5696, 6409, 7124, 7839, 8554, 9270, 9986, 10704,
45  11421, 12138, 12857, 13576, 14295, 15014, 15734, 16455,
46  17176, 17898, 18620, 19343, 20066, 20790, 21514, 22238,
47 };
48 
49 int ff_exp2(uint16_t power)
50 {
51  unsigned int result= exp2a[power>>10] + 0x10000;
52 
53  av_assert2(power <= 0x7fff);
54 
55  result= (result<<3) + ((result*exp2b[(power>>5)&31])>>17);
56  return result + ((result*(power&31)*89)>>22);
57 }
58 #endif
59 
60 /**
61  * Table used to compute log2(x)
62  *
63  * tab_log2[i] = (1<<15) * log2(1 + i/32), i=0..32
64  */
65 static const uint16_t tab_log2[33] =
66 {
67 #ifdef G729_BITEXACT
68  0, 1455, 2866, 4236, 5568, 6863, 8124, 9352,
69  10549, 11716, 12855, 13967, 15054, 16117, 17156, 18172,
70  19167, 20142, 21097, 22033, 22951, 23852, 24735, 25603,
71  26455, 27291, 28113, 28922, 29716, 30497, 31266, 32023, 32767,
72 #else
73  4, 1459, 2870, 4240, 5572, 6867, 8127, 9355,
74  10552, 11719, 12858, 13971, 15057, 16120, 17158, 18175,
75  19170, 20145, 21100, 22036, 22954, 23854, 24738, 25605,
76  26457, 27294, 28116, 28924, 29719, 30500, 31269, 32025, 32769,
77 #endif
78 };
79 
80 int ff_log2_q15(uint32_t value)
81 {
82  uint8_t power_int;
83  uint8_t frac_x0;
84  uint16_t frac_dx;
85 
86  // Stripping zeros from beginning
87  power_int = av_log2(value);
88  value <<= (31 - power_int);
89 
90  // b31 is always non-zero now
91  frac_x0 = (value & 0x7c000000) >> 26; // b26-b31 and [32..63] -> [0..31]
92  frac_dx = (value & 0x03fff800) >> 11;
93 
94  value = tab_log2[frac_x0];
95  value += (frac_dx * (tab_log2[frac_x0+1] - tab_log2[frac_x0])) >> 15;
96 
97  return (power_int << 15) + value;
98 }
99 
100 int64_t ff_dot_product(const int16_t *a, const int16_t *b, int length)
101 {
102  int i;
103  int64_t sum = 0;
104 
105  for (i = 0; i < length; i++)
106  sum += MUL16(a[i], b[i]);
107 
108  return sum;
109 }
110 
111 float ff_dot_productf(const float* a, const float* b, int length)
112 {
113  float sum = 0;
114  int i;
115 
116  for(i=0; i<length; i++)
117  sum += a[i] * b[i];
118 
119  return sum;
120 }
121 
123 {
124  c->dot_productf = ff_dot_productf;
125 
126  if(HAVE_MIPSFPU)
128 }
b
#define b
Definition: input.c:40
avassert.h
MUL16
#define MUL16(ra, rb)
Definition: mathops.h:88
limits.h
ff_log2_q15
int ff_log2_q15(uint32_t value)
Calculate log2(x).
Definition: celp_math.c:80
result
and forward the result(frame or status change) to the corresponding input. If nothing is possible
mathops.h
c
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
ff_celp_math_init
void ff_celp_math_init(CELPMContext *c)
Initialize CELPMContext.
Definition: celp_math.c:122
celp_math.h
a
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:41
av_assert2
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:64
i
int i
Definition: input.c:406
ff_dot_product
int64_t ff_dot_product(const int16_t *a, const int16_t *b, int length)
Calculate the dot product of 2 int16_t vectors.
Definition: celp_math.c:100
common.h
value
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default value
Definition: writing_filters.txt:86
avcodec.h
ff_celp_math_init_mips
void ff_celp_math_init_mips(CELPMContext *c)
Definition: celp_math_mips.c:87
CELPMContext
Definition: celp_math.h:28
ff_exp2
int ff_exp2(uint16_t power)
fixed-point implementation of exp2(x) in [0; 1] domain.
ff_dot_productf
float ff_dot_productf(const float *a, const float *b, int length)
Return the dot product.
Definition: celp_math.c:111
tab_log2
static const uint16_t tab_log2[33]
Table used to compute log2(x)
Definition: celp_math.c:65
av_log2
int av_log2(unsigned v)
Definition: intmath.c:26