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quant.c

/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2007                *
 * by the Xiph.Org Foundation http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

  function:
    last mod: $Id: quant.c 14375 2008-01-06 05:37:33Z tterribe $

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

#include <stdlib.h>
#include <string.h>
#include <ogg/ogg.h>
#include "quant.h"
#include "decint.h"

unsigned OC_DC_QUANT_MIN[2]={4<<2,8<<2};
unsigned OC_AC_QUANT_MIN[2]={2<<2,4<<2};

/*Initializes the dequantization tables from a set of quantizer info.
  Currently the dequantizer (and elsewhere enquantizer) tables are expected to
   be initialized as pointing to the storage reserved for them in the
   oc_theora_state (resp. oc_enc_ctx) structure.
  If some tables are duplicates of others, the pointers will be adjusted to
   point to a single copy of the tables, but the storage for them will not be
   freed.
  If you're concerned about the memory footprint, the obvious thing to do is
   to move the storage out of its fixed place in the structures and allocate
   it on demand.
  However, a much, much better option is to only store the quantization
   matrices being used for the current frame, and to recalculate these as the
   qi values change between frames (this is what VP3 did).*/
void oc_dequant_tables_init(oc_quant_table *_dequant[2][3],
 int _pp_dc_scale[64],const th_quant_info *_qinfo){
  int          qti; /* coding mode: intra or inter */
  int          pli; /* Y U V */
  for(qti=0;qti<2;qti++){
    for(pli=0;pli<3;pli++){
      oc_quant_tables stage;

      int qi;  /* quality index */
      int qri; /* range iterator */
      
      for(qi=0,qri=0; qri<=_qinfo->qi_ranges[qti][pli].nranges; qri++){
      th_quant_base base;
      
      ogg_uint32_t      q;
      int               qi_start;
      int               qi_end;
      int               ci;
      memcpy(base,_qinfo->qi_ranges[qti][pli].base_matrices[qri],
             sizeof(base));

      qi_start=qi;
      if(qri==_qinfo->qi_ranges[qti][pli].nranges)
        qi_end=qi+1;
      else 
        qi_end=qi+_qinfo->qi_ranges[qti][pli].sizes[qri];
      
      /* Iterate over quality indicies in this range */
      for(;;){
        
        /*In the original VP3.2 code, the rounding offset and the size of the
          dead zone around 0 were controlled by a "sharpness" parameter.
          The size of our dead zone is now controlled by the per-coefficient
          quality thresholds returned by our HVS module.
          We round down from a more accurate value when the quality of the
          reconstruction does not fall below our threshold and it saves bits.
          Hence, all of that VP3.2 code is gone from here, and the remaining
          floating point code has been implemented as equivalent integer code
          with exact precision.*/

        /* for postprocess, not dequant */
        if(_pp_dc_scale!=NULL)
          _pp_dc_scale[qi]=(int)((ogg_uint32_t)_qinfo->dc_scale[qi]*base[0]/160);

        /*Scale DC the coefficient from the proper table.*/
        q=((ogg_uint32_t)_qinfo->dc_scale[qi]*base[0]/100)<<2;
        q=OC_CLAMPI(OC_DC_QUANT_MIN[qti],q,OC_QUANT_MAX);
        stage[qi][0]=(ogg_uint16_t)q;
        
        /*Now scale AC coefficients from the proper table.*/
        for(ci=1;ci<64;ci++){
          q=((ogg_uint32_t)_qinfo->ac_scale[qi]*base[ci]/100)<<2;
          q=OC_CLAMPI(OC_AC_QUANT_MIN[qti],q,OC_QUANT_MAX);
          stage[qi][ci]=(ogg_uint16_t)q;
        }
        
        if(++qi>=qi_end)break;
        
        /*Interpolate the next base matrix.*/
        for(ci=0;ci<64;ci++){
          base[ci]=(unsigned char)
            ((2*((qi_end-qi)*_qinfo->qi_ranges[qti][pli].base_matrices[qri][ci]+
               (qi-qi_start)*_qinfo->qi_ranges[qti][pli].base_matrices[qri+1][ci])
            +_qinfo->qi_ranges[qti][pli].sizes[qri])/
             (2*_qinfo->qi_ranges[qti][pli].sizes[qri]));
        }
      }
      }

      /* Staging matricies complete; commit to memory only if this
       isn't a duplicate of a preceeding plane. This simple check
       helps us improve cache coherency later.*/
      {
      int dupe = 0;
      int i,j;
      for(i=0;i<=qti;i++){
        for(j=0;j<(i<qti?3:pli);j++){
          if(!memcmp(stage,_dequant[i][j],sizeof(stage))){
            dupe = 1;
            break;
          }
        }
        if(dupe)break;
      }
      if(dupe){
        _dequant[qti][pli]=_dequant[i][j];
      }else{
        memcpy(_dequant[qti][pli],stage,sizeof(stage));
      }
      }
    }
  }

#ifdef _TH_DEBUG_
  int i, j, k, l;
  /* dump the calculated quantizer tables */
  for(i=0;i<2;i++){
    for(j=0;j<3;j++){
      for(k=0;k<64;k++){
      TH_DEBUG("quantizer table [%s][%s][Q%d] = {",
             (i==0?"intra":"inter"),(j==0?"Y":(j==1?"U":"V")),k);
      for(l=0;l<64;l++){
        if((l&7)==0)
          TH_DEBUG("\n   ");
        TH_DEBUG("%4d ",_dequant[i][j][k][l]);
      }
      TH_DEBUG("}\n");
      }
    }
  }
#endif

}

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