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fixed_dsp.h
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29  * Author: Nedeljko Babic (nbabic@mips.com)
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47 
48 #ifndef AVUTIL_FIXED_DSP_H
49 #define AVUTIL_FIXED_DSP_H
50 
51 #include <stdint.h>
52 #include "attributes.h"
53 #include "common.h"
54 #include "libavcodec/mathops.h"
55 
56 typedef struct AVFixedDSPContext {
57  /**
58  * Overlap/add with window function.
59  * Used primarily by MDCT-based audio codecs.
60  * Source and destination vectors must overlap exactly or not at all.
61  *
62  * @param dst result vector
63  * constraints: 16-byte aligned
64  * @param src0 first source vector
65  * constraints: 16-byte aligned
66  * @param src1 second source vector
67  * constraints: 16-byte aligned
68  * @param win half-window vector
69  * constraints: 16-byte aligned
70  * @param len length of vector
71  * constraints: multiple of 4
72  * @param bits scaling parameter
73  *
74  */
75  void (*vector_fmul_window_scaled)(int16_t *dst, const int32_t *src0, const int32_t *src1, const int32_t *win, int len, uint8_t bits);
76 
77  /**
78  * Overlap/add with window function.
79  * Used primarily by MDCT-based audio codecs.
80  * Source and destination vectors must overlap exactly or not at all.
81  *
82  * @param dst result vector
83  * constraints: 32-byte aligned
84  * @param src0 first source vector
85  * constraints: 16-byte aligned
86  * @param src1 second source vector
87  * constraints: 16-byte aligned
88  * @param win half-window vector
89  * constraints: 16-byte aligned
90  * @param len length of vector
91  * constraints: multiple of 4
92  */
93  void (*vector_fmul_window)(int32_t *dst, const int32_t *src0, const int32_t *src1, const int32_t *win, int len);
94 
96 
97 /**
98  * Allocate and initialize a fixed DSP context.
99  * note: should be freed with a av_free call when no longer needed.
100  *
101  * @param strict setting to non-zero avoids using functions which may not be IEEE-754 compliant
102  */
104 
105 /**
106  * Calculate the square root
107  *
108  * @param x input fixed point number
109  *
110  * @param bits format of fixed point number (32 - bits).bits
111  *
112  * note: input is normalized to (0, 1) fixed point value
113  */
114 
115 static av_always_inline int fixed_sqrt(int x, int bits)
116 {
117  int retval, bit_mask, guess, square, i;
118  int64_t accu;
119  int shift1 = 30 - bits;
120  int shift2 = bits - 15;
121 
122  if (shift1 > 0) retval = ff_sqrt(x << shift1);
123  else retval = ff_sqrt(x >> -shift1);
124 
125  if (shift2 > 0) {
126  retval = retval << shift2;
127  bit_mask = (1 << (shift2 - 1));
128 
129  for (i=0; i<shift2; i++){
130  guess = retval + bit_mask;
131  accu = (int64_t)guess * guess;
132  square = (int)((accu + bit_mask) >> bits);
133  if (x >= square)
134  retval += bit_mask;
135  bit_mask >>= 1;
136  }
137 
138  }
139  else retval >>= (-shift2);
140 
141  return retval;
142 }
143 
144 #endif /* AVUTIL_FIXED_DSP_H */