1 /******************************************************************************
2 *
3 * Copyright (C) 2015 The Android Open Source Project
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at:
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 *****************************************************************************
18 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore
19 */
20 /**
21 *******************************************************************************
22 * @file
23 * icv_variance.c
24 *
25 * @brief
26 * This file contains the functions to compute variance
27 *
28 * @author
29 * Ittiam
30 *
31 * @par List of Functions:
32 * icv_variance_8x4()
33 *
34 * @remarks
35 * None
36 *
37 *******************************************************************************
38 */
39 /*****************************************************************************/
40 /* File Includes */
41 /*****************************************************************************/
42 /* System include files */
43 #include <stdio.h>
44 #include <stdint.h>
45 #include <string.h>
46 #include <stdlib.h>
47 #include <assert.h>
48
49
50 /* User include files */
51 #include "icv_datatypes.h"
52 #include "icv_macros.h"
53 #include "icv_platform_macros.h"
54 #include "icv.h"
55
56 /**
57 *******************************************************************************
58 *
59 * @brief
60 * Computes variance of a given 8x4 block
61 *
62 * @par Description
63 * Compute variance of a given 8x4 block
64 *
65 * @param[in] pu1_src
66 * Source
67 *
68 * @param[in] src_strd
69 * Source stride
70 *
71 * @param[in] wd
72 * Assumed to be 8
73 *
74 * @param[in] ht
75 * Assumed to be 4
76 *
77 * @returns
78 * Variance
79 *
80 * @remarks
81 *
82 *******************************************************************************
83 */
icv_variance_8x4(UWORD8 * pu1_src,WORD32 src_strd,WORD32 wd,WORD32 ht)84 WORD32 icv_variance_8x4(UWORD8 *pu1_src, WORD32 src_strd, WORD32 wd, WORD32 ht)
85 {
86 WORD32 sum;
87 WORD32 sum_sqr;
88 WORD32 blk_sz;
89 WORD32 vrnc;
90 WORD32 i;
91 WORD32 j;
92 UNUSED(wd);
93 UNUSED(ht);
94
95 ASSERT(wd == 8);
96 ASSERT(ht == 4);
97
98 sum = 0;
99 sum_sqr = 0;
100
101 blk_sz = 8 * 4;
102
103 /*************************************************************************/
104 /* variance */
105 /* var = (n * SUM(x_i^2) - (SUM(x_i))^2) / (n^2); */
106 /*************************************************************************/
107
108 /*************************************************************************/
109 /* The outer-loop runs for BLK_HT/2 times, because it */
110 /* calculates the variance only for field area not frame one. */
111 /*************************************************************************/
112 for(j = 0; j < 4; j ++)
113 {
114 for(i = 0; i < 8; i++)
115 {
116 sum_sqr += (*pu1_src) * (*pu1_src);
117 sum += *pu1_src++;
118 }
119 pu1_src += (src_strd - 8);
120 }
121
122 vrnc = ((sum_sqr * blk_sz) - (sum * sum)) / (blk_sz * blk_sz);
123
124 return vrnc;
125 }
126
127