| /****************************************************************************** |
| * |
| * 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; |
| } |
| |