quant_h263.cpp

来自「gaca源码」· C++ 代码 · 共 86 行

/*****************************************************************************
 *
 *  XVID MPEG-4 VIDEO CODEC
 *  - MPEG4 Quantization H263 implementation -
 *
 *  Copyright(C) 2001-2003 Peter Ross <[e-mail]>
 *
 *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * $Id: quant_h263.cpp,v 1.1.1.1 2005/07/13 14:36:16 jeanlf Exp $
 *
 ****************************************************************************/

#include "global.h"
#include "quant.h"

//----------------------------
/* dequantize intra-block & clamp to [-2048,2047]
 */
void dequant_h263_intra(int *data, const int *coeff, dword quant, dword dcscalar, const dword *mpeg_quant_matrices){

   const int quant_m_2 = quant << 1;
   const int quant_add = (quant & 1 ? quant : quant - 1);

   data[0] = *coeff++ * dcscalar;
   if(data[0] < -2048){
      data[0] = -2048;
   }//else
   if(data[0] > 2047){
      data[0] = 2047;
   }
   for(int i = 1; i < 64; i++){
      int acLevel = *coeff++;

      if(acLevel == 0){
         data[i] = 0;
      }else
      if(acLevel < 0){
         acLevel = quant_m_2 * -acLevel + quant_add;
         data[i] = (acLevel <= 2048 ? -acLevel : -2048);
      }else{
         acLevel = quant_m_2 * acLevel + quant_add;
         data[i] = (acLevel <= 2047 ? acLevel : 2047);
      }
   }
}

//----------------------------
/* dequantize inter-block & clamp to [-2048,2047]
 */

void dequant_h263_inter(int *data, const int *coeff, dword quant, const dword *mpeg_quant_matrices){

   const dword quant_m_2 = quant << 1;
   const dword quant_add = (quant & 1 ? quant : quant - 1);

   for(int i = 0; i < 64; i++){
      int acLevel = *coeff++;

      if(acLevel == 0){
         data[i] = 0;
      }else
      if(acLevel < 0){
         acLevel = acLevel * quant_m_2 - quant_add;
         data[i] = (acLevel >= -2048 ? acLevel : -2048);
      }else{
         acLevel = acLevel * quant_m_2 + quant_add;
         data[i] = (acLevel <= 2047 ? acLevel : 2047);
      }
   }
}

//----------------------------