FFmpeg
celp_math.h
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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 #ifndef AVCODEC_CELP_MATH_H
24 #define AVCODEC_CELP_MATH_H
25 
26 #include <stdint.h>
27 
28 typedef struct CELPMContext {
29  /**
30  * Return the dot product.
31  * @param a input data array
32  * @param b input data array
33  * @param length number of elements
34  *
35  * @return dot product = sum of elementwise products
36  */
37  float (*dot_productf)(const float* a, const float* b, int length);
38 
40 
41 /**
42  * Initialize CELPMContext.
43  */
46 
47 /**
48  * fixed-point implementation of exp2(x) in [0; 1] domain.
49  * @param power argument to exp2, 0 <= power <= 0x7fff
50  *
51  * @return value of (1<<20) * exp2(power / (1<<15))
52  * 0x8000c <= result <= 0xfffea
53  */
54 int ff_exp2(uint16_t power);
55 
56 /**
57  * Calculate log2(x).
58  * @param value function argument, 0 < value <= 7fff ffff
59  *
60  * @return value of (1<<15) * log2(value)
61  */
62 int ff_log2_q15(uint32_t value);
63 
64 /**
65  * Calculate the dot product of 2 int16_t vectors.
66  * @param a input data array
67  * @param b input data array
68  * @param length number of elements
69  *
70  * @return dot product = sum of elementwise products
71  */
72 int64_t ff_dot_product(const int16_t *a, const int16_t *b, int length);
73 
74 /**
75  * Shift value left or right depending on sign of offset parameter.
76  * @param value value to shift
77  * @param offset shift offset
78  *
79  * @return value << offset, if offset>=0; value >> -offset - otherwise
80  */
81 static inline int bidir_sal(int value, int offset)
82 {
83  if(offset < 0) return value >> -offset;
84  else return value << offset;
85 }
86 
87 /**
88  * Return the dot product.
89  * @param a input data array
90  * @param b input data array
91  * @param length number of elements
92  *
93  * @return dot product = sum of elementwise products
94  */
95 float ff_dot_productf(const float* a, const float* b, int length);
96 
97 #endif /* AVCODEC_CELP_MATH_H */
void ff_celp_math_init_mips(CELPMContext *c)
float(* dot_productf)(const float *a, const float *b, int length)
Return the dot product.
Definition: celp_math.h:37
int ff_exp2(uint16_t power)
fixed-point implementation of exp2(x) in [0; 1] domain.
Definition: celp_math.c:48
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
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 offset
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
GLsizei GLboolean const GLfloat * value
Definition: opengl_enc.c:108
float ff_dot_productf(const float *a, const float *b, int length)
Return the dot product.
Definition: celp_math.c:109
GLsizei GLsizei * length
Definition: opengl_enc.c:114
#define b
Definition: input.c:41
void ff_celp_math_init(CELPMContext *c)
Initialize CELPMContext.
Definition: celp_math.c:120
static int bidir_sal(int value, int offset)
Shift value left or right depending on sign of offset parameter.
Definition: celp_math.h:81
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:98
int ff_log2_q15(uint32_t value)
Calculate log2(x).
Definition: celp_math.c:78