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注：问号以及未注释部分 会在x265-1.8版本内更新 

/***************************************************************************** * Copyright (C) 2013 x265 project * * Authors: Gopu Govindaswamy 
   
     * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02111, USA. * * This program is also available under a commercial proprietary license. * For more information, contact us at license @ x265.com. *****************************************************************************/#include "picyuv.h"#include "lowres.h"#include "mv.h"using namespace x265;//本文件提供关于视频图像下采样的一个功能接口//Lowres 申请空间、释放内存、初始化、下采样图像及扩边等/** 函数功能   ： 初始化数据，并申请空间内存/*  调用范围   ： 只Frame::create函数中被调用* \参数 origPic： Frame.m_fencPic 原始帧YUV数据* \返回        ： 是否申请内存成功 */bool Lowres::create(PicYuv *origPic, int _bframes, bool bAQEnabled){    isLowres = true;                  //告知父类ReferencePlanes 当前是lowresolution    bframes = _bframes;                  width = origPic->m_picWidth / 2; //1/2下采样宽度    lines = origPic->m_picHeight / 2;//1/2下采样高度    lumaStride = width + 2 * origPic->m_lumaMarginX;    if (lumaStride & 31)        lumaStride += 32 - (lumaStride & 31);   //保证当前下采样视频步长时32的整数倍    int cuWidth = (width + X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;    int cuHeight = (lines + X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;    int cuCount = cuWidth * cuHeight;    /* rounding the width to multiple of lowres CU size */    width = cuWidth * X265_LOWRES_CU_SIZE;    lines = cuHeight * X265_LOWRES_CU_SIZE;    size_t planesize = lumaStride * (lines + 2 * origPic->m_lumaMarginY);    size_t padoffset = lumaStride * origPic->m_lumaMarginY + origPic->m_lumaMarginX;    if (bAQEnabled)    {        CHECKED_MALLOC(qpAqOffset, double, cuCount);        CHECKED_MALLOC(invQscaleFactor, int, cuCount);        CHECKED_MALLOC(qpCuTreeOffset, double, cuCount);    }    CHECKED_MALLOC(propagateCost, uint16_t, cuCount);    /* allocate lowres buffers */    CHECKED_MALLOC_ZERO(buffer[0], pixel, 4 * planesize); //这里需要申请4个buffer ，因为将要通过4 hpel下采样得到4份1/2亮度    buffer[1] = buffer[0] + planesize;    buffer[2] = buffer[1] + planesize;    buffer[3] = buffer[2] + planesize;    lowresPlane[0] = buffer[0] + padoffset;    lowresPlane[1] = buffer[1] + padoffset;    lowresPlane[2] = buffer[2] + padoffset;    lowresPlane[3] = buffer[3] + padoffset;    CHECKED_MALLOC(intraCost, int32_t, cuCount);    CHECKED_MALLOC(intraMode, uint8_t, cuCount);    for (int i = 0; i < bframes + 2; i++)    {        for (int j = 0; j < bframes + 2; j++)        {            CHECKED_MALLOC(rowSatds[i][j], int32_t, cuHeight);            CHECKED_MALLOC(lowresCosts[i][j], uint16_t, cuCount);        }    }    for (int i = 0; i < bframes + 1; i++)    {        CHECKED_MALLOC(lowresMvs[0][i], MV, cuCount);        CHECKED_MALLOC(lowresMvs[1][i], MV, cuCount);        CHECKED_MALLOC(lowresMvCosts[0][i], int32_t, cuCount);        CHECKED_MALLOC(lowresMvCosts[1][i], int32_t, cuCount);    }    return true;fail:    return false;}/** 函数功能   ： 释放空间内存/*  调用范围   ： 只Frame::destroy函数中被调用* \返回        ： null */void Lowres::destroy(){    X265_FREE(buffer[0]);    X265_FREE(intraCost);    X265_FREE(intraMode);    for (int i = 0; i < bframes + 2; i++)    {        for (int j = 0; j < bframes + 2; j++)        {            X265_FREE(rowSatds[i][j]);            X265_FREE(lowresCosts[i][j]);        }    }    for (int i = 0; i < bframes + 1; i++)    {        X265_FREE(lowresMvs[0][i]);        X265_FREE(lowresMvs[1][i]);        X265_FREE(lowresMvCosts[0][i]);        X265_FREE(lowresMvCosts[1][i]);    }    X265_FREE(qpAqOffset);    X265_FREE(invQscaleFactor);    X265_FREE(qpCuTreeOffset);    X265_FREE(propagateCost);}/** 函数功能   ： 初始化信息，并进行下采样和扩边/*  调用范围   ： 只void PreLookaheadGroup::processTasks函数中被调用* \返回        ： null */// (re) initialize lowres statevoid Lowres::init(PicYuv *origPic, int poc){    bLastMiniGopBFrame = false;    bScenecut = true;  // could be a scene-cut, until ruled out by flash detection    bKeyframe = false; // Not a keyframe unless identified by lookahead    frameNum = poc;    leadingBframes = 0;    indB = 0;    satdCost = (int64_t)-1;    memset(costEst, -1, sizeof(costEst));    memset(weightedCostDelta, 0, sizeof(weightedCostDelta));    if (qpAqOffset && invQscaleFactor)        memset(costEstAq, -1, sizeof(costEstAq));    for (int y = 0; y < bframes + 2; y++)        for (int x = 0; x < bframes + 2; x++)            rowSatds[y][x][0] = -1;    for (int i = 0; i < bframes + 1; i++)    {        lowresMvs[0][i][0].x = 0x7FFF;        lowresMvs[1][i][0].x = 0x7FFF;    }    for (int i = 0; i < bframes + 2; i++)        intraMbs[i] = 0;    /* downscale and generate 4 hpel planes for lookahead */    /* 查看 非asm函数frame_init_lowres_core       这样做的目的是更好的通过1/2下采样视频的编码估计原始视频编码状态       将亮度分四种方法进行1/2下采样       原始点：       82  89  86  86  93        85  89  99 101 113        96  97  97 100 104        106 108 107 111 109        127 156 133 139 137              0: 在行列选择偶数像素点为基准并选择相邻的右边、下边、右下机本身4个点作平均       * * + +       * * + +       - - # #       - - # #       87  94       102 104       87 = ((((82 + 85 + 1) >> 1) + ((89 + 89 + 1) >> 1) + 1) >> 1)       94 = ((((86 + 99 + 1) >> 1) + ((86 + 101 + 1) >> 1) + 1) >> 1)       102= ((((96 + 106 + 1) >> 1) + ((97 + 108 + 1) >> 1) + 1) >> 1)       104 = ((((97 + 107 + 1) >> 1) + ((100 + 111 + 1) >> 1) + 1) >> 1)       h: 在行选择偶数像素点，在列选择奇数像素点为基准并选择相邻的右边、下边、右下机本身4个点作平均       = * * = + +       = * * = + +       = - - = # #       = - - = # #       91  99        103 107        91 = ((((89 + 89 + 1) >> 1) + ((86 + 99 + 1) >> 1) + 1) >> 1)        99 = ((((86 + 101 + 1) >> 1) + ((93 + 113 + 1) >> 1) + 1) >> 1)        v: 在行选择奇数像素点，在列选择偶数像素点为基准并选择相邻的右边、下边、右下机本身4个点作平均       = = = =       * * + +       * * + +       = = = =       - - # #       - - # #       92 100        125 123        92 = ((((85 + 96 + 1) >> 1) + ((89 + 97 + 1) >> 1) + 1) >> 1)        在行列选择奇数像素点为基准并选择相邻的右边、下边、右下机本身4个点作平均       = = = = = =       = * * = + +       = * * = + +       = = = = = =       = - - = # #       = - - = # #       96 105       126 124       96 = ((((89 + 97 + 1) >> 1) + ((99 + 97 + 1) >> 1) + 1) >> 1)     **/    primitives.frameInitLowres(origPic->m_picOrg[0],                               lowresPlane[0], lowresPlane[1], lowresPlane[2], lowresPlane[3],                                origPic->m_stride, lumaStride, width, lines);    /* extend hpel planes for motion search */    extendPicBorder(lowresPlane[0], lumaStride, width, lines, origPic->m_lumaMarginX, origPic->m_lumaMarginY);//扩边    extendPicBorder(lowresPlane[1], lumaStride, width, lines, origPic->m_lumaMarginX, origPic->m_lumaMarginY);    extendPicBorder(lowresPlane[2], lumaStride, width, lines, origPic->m_lumaMarginX, origPic->m_lumaMarginY);    extendPicBorder(lowresPlane[3], lumaStride, width, lines, origPic->m_lumaMarginX, origPic->m_lumaMarginY);    fpelPlane[0] = lowresPlane[0];}
   

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