x265-1.7版本-encoder/bitcost.cpp注释
2016-01-23 11:25
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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: Steve Borho <steve@borho.org> * * 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 "common.h" #include "primitives.h" #include "bitcost.h" using namespace x265; /** 函数功能 :建立当前qp下的MVD占用的cost:λ*bits = 2^(qp/6-2) * s_bitsizes[i] * \参数 qp :当前ME下的qp大小 * \返回 :null * */ void BitCost::setQP(unsigned int qp) { if (!s_costs[qp]) //如果当前还没有申请空间并初始化,在下面将其申请空间并初始化 s_costs,所有的me共有,每个qp只初始化一次 { ScopedLock s(s_costCalcLock); //加锁防止多线程读取脏数据 // Now that we have acquired the lock, check again if another thread calculated // this row while we were blocked if (!s_costs[qp]) { x265_emms(); // just to be safe 清除MMX寄存器中的内容,即初始化(以避免和浮点数操作发生冲突)。 CalculateLogs(); //建立MVD估计占用bits表格,例如:当前MV.x = 3 ,则其占用bits 为 s_bitsizes[3] 2*(log2(3+1))+e-1 s_costs[qp] = new uint16_t[4 * BC_MAX_MV + 1] + 2 * BC_MAX_MV; //申请空间为4*32768+1 并指向当前地址2*32768 double lambda = x265_lambda_tab[qp]; //2^(qp/6-2) // estimate same cost for negative and positive MVD for (int i = 0; i <= 2 * BC_MAX_MV; i++) s_costs[qp][i] = s_costs[qp][-i] = (uint16_t)X265_MIN(s_bitsizes[i] * lambda + 0.5f, (1 << 16) - 1);//其值为 s_bitsizes[i] * lambda 四舍五入取整 } } m_cost = s_costs[qp]; //将m_cost指针指向当前qp所对应的MVD cost表(MVD为0的位置),在计算MVD的cost就是通过MVD寻址m_cost表 //在setMVP()中,将m_cost_mvx/m_cost_mvy赋值为MVP的cost表地址,在ME中根据MVD来寻址m_cost_mvx/m_cost_mvy,即可以得到mvx/mvy的cost } /*** * Class static data and methods */ uint16_t *BitCost::s_costs[BC_MAX_QP]; //所有的me共有,每个qp只初始化一次 float *BitCost::s_bitsizes;//申请空间大小为 2*32768+1 MVD估计占用bits表格,例如:当前MV.x = 3 ,则其占用bits 为 s_bitsizes[3] 2*(log2(3+1))+e-1 /* s_bitsizes[0] = e - 2 s_bitsizes[i]= 2*(log2(i+1))+e-1 log2 表示以2为底 s_bitsizes[1] = 2log2(2) + e -1 **/ Lock BitCost::s_costCalcLock;//多线程锁 /** 函数功能 :建立MVD估计占用bits表格,例如:当前MV.x = 3 ,则其占用bits 为 s_bitsizes[3] 2*(log2(3+1))+e-1 * \返回 :null * */ void BitCost::CalculateLogs() { if (!s_bitsizes) //没有申请空间,在此申请,所有ME共有,所以一般只进入一次 { s_bitsizes = new float[2 * BC_MAX_MV + 1]; //空间大小:32786*2+1 s_bitsizes[0] = 0.718f; float log2_2 = 2.0f / log(2.0f); // 2 x 1/log(2) double log (double); 以e为底的对数 e = 2.718281828459 for (int i = 1; i <= 2 * BC_MAX_MV; i++) s_bitsizes[i] = log((float)(i + 1)) * log2_2 + 1.718f; /* s_bitsizes[0] = e - 2, s_bitsizes[i]= 2*(log2(i+1))+e-1, log2表示以2为底 s_bitsizes[1] = 2log2(2) + e -1 **/ } } /** 函数功能 : 释放空间内存 * \返回 : null */ void BitCost::destroy() { for (int i = 0; i < BC_MAX_QP; i++) { if (s_costs[i]) { delete [] (s_costs[i] - 2 * BC_MAX_MV); s_costs[i] = 0; } } delete [] s_bitsizes; s_bitsizes = 0; }
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