/******************************************************************************
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*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*****************************************************************************
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* Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore
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*/
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/**
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*******************************************************************************
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* @file
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* icv_variance.c
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*
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* @brief
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* This file contains the functions to compute variance
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*
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* @author
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* Ittiam
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*
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* @par List of Functions:
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* icv_variance_8x4()
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*
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* @remarks
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* None
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*
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*******************************************************************************
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*/
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/*****************************************************************************/
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/* File Includes */
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/*****************************************************************************/
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/* System include files */
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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#include <assert.h>
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/* User include files */
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#include "icv_datatypes.h"
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#include "icv_macros.h"
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#include "icv_platform_macros.h"
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#include "icv.h"
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/**
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*******************************************************************************
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*
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* @brief
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* Computes variance of a given 8x4 block
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*
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* @par Description
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* Compute variance of a given 8x4 block
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*
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* @param[in] pu1_src
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* Source
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*
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* @param[in] src_strd
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* Source stride
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*
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* @param[in] wd
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* Assumed to be 8
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*
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* @param[in] ht
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* Assumed to be 4
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*
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* @returns
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* Variance
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*
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* @remarks
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*
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*******************************************************************************
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*/
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WORD32 icv_variance_8x4(UWORD8 *pu1_src, WORD32 src_strd, WORD32 wd, WORD32 ht)
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{
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WORD32 sum;
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WORD32 sum_sqr;
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WORD32 blk_sz;
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WORD32 vrnc;
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WORD32 i;
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WORD32 j;
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UNUSED(wd);
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UNUSED(ht);
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ASSERT(wd == 8);
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ASSERT(ht == 4);
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sum = 0;
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sum_sqr = 0;
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blk_sz = 8 * 4;
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/*************************************************************************/
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/* variance */
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/* var = (n * SUM(x_i^2) - (SUM(x_i))^2) / (n^2); */
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/*************************************************************************/
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/*************************************************************************/
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/* The outer-loop runs for BLK_HT/2 times, because it */
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/* calculates the variance only for field area not frame one. */
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/*************************************************************************/
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for(j = 0; j < 4; j ++)
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{
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for(i = 0; i < 8; i++)
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{
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sum_sqr += (*pu1_src) * (*pu1_src);
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sum += *pu1_src++;
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}
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pu1_src += (src_strd - 8);
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}
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vrnc = ((sum_sqr * blk_sz) - (sum * sum)) / (blk_sz * blk_sz);
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return vrnc;
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}
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