/******************************************************************************

 *

 * Copyright (C) 2015 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at:

 *

 * http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 *

 *****************************************************************************

 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore

*/

/**

*******************************************************************************

* @file

*  icv_variance.c

*

* @brief

*  This file contains the functions to compute variance

*

* @author

*  Ittiam

*

* @par List of Functions:

*  icv_variance_8x4()

*

* @remarks

*  None

*

*******************************************************************************

*/

/*****************************************************************************/

/* File Includes                                                             */

/*****************************************************************************/

/* System include files */

#include <stdio.h>

#include <stdint.h>

#include <string.h>

#include <stdlib.h>

#include <assert.h>

/* User include files */

#include "icv_datatypes.h"

#include "icv_macros.h"

#include "icv_platform_macros.h"

#include "icv.h"

/**

*******************************************************************************

*

* @brief

*  Computes variance of a given 8x4 block

*

* @par   Description

*  Compute variance of a given 8x4 block

*

* @param[in] pu1_src

*  Source

*

* @param[in] src_strd

*  Source stride

*

* @param[in] wd

*  Assumed to be 8

*

* @param[in] ht

*  Assumed to be 4

*

* @returns

*  Variance

*

* @remarks

*

*******************************************************************************

*/

WORD32 icv_variance_8x4(UWORD8 *pu1_src, WORD32 src_strd, WORD32 wd, WORD32 ht)

{

    WORD32 sum;

    WORD32 sum_sqr;

    WORD32 blk_sz;

    WORD32 vrnc;

    WORD32 i;

    WORD32 j;

    UNUSED(wd);

    UNUSED(ht);

    ASSERT(wd == 8);

    ASSERT(ht == 4);

    sum     = 0;

    sum_sqr = 0;

    blk_sz = 8 * 4;

    /*************************************************************************/

    /* variance                                                              */

    /* var = (n * SUM(x_i^2) - (SUM(x_i))^2) / (n^2);                        */

    /*************************************************************************/

    /*************************************************************************/

    /* The outer-loop runs for BLK_HT/2 times, because it                    */

    /* calculates the variance only for field area not frame one.            */

    /*************************************************************************/

    for(j = 0; j < 4; j ++)

    {

        for(i = 0; i < 8; i++)

        {

            sum_sqr += (*pu1_src) * (*pu1_src);

            sum     +=  *pu1_src++;

        }

        pu1_src += (src_strd - 8);

    }

    vrnc = ((sum_sqr * blk_sz) - (sum * sum)) / (blk_sz * blk_sz);

    return vrnc;

}