decoder.c

MPEG-4编解码的实现(包括MPEG4视音频编解码)

/*
***********************************************************************
* COPYRIGHT AND WARRANTY INFORMATION
*
* Copyright 2001, International Telecommunications Union, Geneva
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/*! 
 *************************************************************************************
 * \file decoder.c
 *
 * \brief
 *    Contains functions that implement the "decoders in the encoder" concept for the
 *    rate-distortion optimization with losses.
 * \date
 *    October 22nd, 2001
 *
 * \author
 *    Main contributors (see contributors.h for copyright, address and 
 *    affiliation details)
 *    - Dimitrios Kontopodis                    <[e-mail]>
 *************************************************************************************
 */

#include <stdlib.h>
#include <memory.h>

#include "global.h"
#include "refbuf.h"
#include "rdopt.h"

/*! 
 *************************************************************************************
 * \brief
 *    decodes one macroblock at one simulated decoder 
 *
 * \param decoder
 *    The id of the decoder
 *
 * \param mode
 *    encoding mode of the MB
 *
 * \param ref
 *    reference frame index
 *
 * \note
 *    Gives the expected value in the decoder of one MB. This is done based on the 
 *    stored reconstructed residue resY[][], the reconstructed values imgY[][]
 *    and the motion vectors. The decoded MB is moved to decY[][].
 *************************************************************************************
 */
void decode_one_macroblock(int decoder, int mode, int ref)
{
  int i,j,block_y,block_x;
  int ref_inx;
  int mv[2][BLOCK_MULTIPLE][BLOCK_MULTIPLE];
  int resY_tmp[MB_BLOCK_SIZE][MB_BLOCK_SIZE];

  int inter = (mode >= MBMODE_INTER16x16    && mode <= MBMODE_INTER4x4    && img->type!=B_IMG);

  if (img->number==0)
  {
    for(i=0;i<MB_BLOCK_SIZE;i++)
      for(j=0;j<MB_BLOCK_SIZE;j++)
        decY[decoder][img->pix_y+j][img->pix_x+i]=imgY[img->pix_y+j][img->pix_x+i];
  }
  else
  {
    if (mode==MBMODE_COPY)
    {
      for(i=0;i<MB_BLOCK_SIZE;i++)
        for(j=0;j<MB_BLOCK_SIZE;j++)
          resY_tmp[j][i]=0;

      /* Set motion vectors to zero */
      for (block_y=0; block_y<BLOCK_MULTIPLE; block_y++)
        for (block_x=0; block_x<BLOCK_MULTIPLE; block_x++)
          for (i=0;i<2;i++)
            mv[i][block_y][block_x]=0;

    }
    else
    {
    /* Copy motion vectors and residues to local arrays mv, resY_tmp, resUV_tmp */
      for (block_y=0; block_y<BLOCK_MULTIPLE; block_y++)
        for (block_x=0; block_x<BLOCK_MULTIPLE; block_x++)
          for (i=0;i<2;i++)
            mv[i][block_y][block_x]=tmp_mv[i][img->block_y+block_y][img->block_x+block_x+4];
          
      for(i=0;i<MB_BLOCK_SIZE;i++)
        for(j=0;j<MB_BLOCK_SIZE;j++)
          resY_tmp[j][i]=resY[j][i];
    }
  
    
    /* Decode Luminance */
    if (inter || mode==MBMODE_COPY)  
    {
      for (block_y=img->block_y ; block_y < img->block_y+BLOCK_MULTIPLE ; block_y++)
        for (block_x=img->block_x ; block_x < img->block_x+BLOCK_MULTIPLE ; block_x++)
        {

          ref_inx = (img->number-ref-1)%img->no_multpred;
          
          Get_Reference_Block(decref[decoder][ref_inx],
                                block_y, block_x,
                                mv[0][block_y-img->block_y][block_x-img->block_x],
                                mv[1][block_y-img->block_y][block_x-img->block_x], 
                                RefBlock);
          for (j=0;j<BLOCK_SIZE;j++)
            for (i=0;i<BLOCK_SIZE;i++)
            {
              if (RefBlock[j][i] != UMVPelY_14 (mref[ref_inx],
                                                (block_y*4+j)*4+mv[1][block_y-img->block_y][block_x-img->block_x],
                                                (block_x*4+i)*4+mv[0][block_y-img->block_y][block_x-img->block_x]))
              ref_inx = (img->number-ref-1)%img->no_multpred;
              decY[decoder][block_y*BLOCK_SIZE + j][block_x*BLOCK_SIZE + i] = 
                                  resY_tmp[(block_y-img->block_y)*BLOCK_SIZE + j]
                                          [(block_x-img->block_x)*BLOCK_SIZE + i]
                                  + RefBlock[j][i];
            }
        }
    }
    else 
    {
      /* Intra Refresh - Assume no spatial prediction */
      for (j=0;j<MB_BLOCK_SIZE;j++)
        for (i=0;i<MB_BLOCK_SIZE;i++)
          decY[decoder][img->pix_y + j][img->pix_x + i] = imgY[img->pix_y + j][img->pix_x + i];
    }
  }
}


/*! 
 *************************************************************************************
 * \brief
 *    Finds the reference MB given the decoded reference frame
 * \note
 *    This is based on the function UnifiedOneForthPix, only it is modified to
 *    be used at the "many decoders in the encoder" RD optimization. In this case
 *    we dont want to keep full upsampled reference frames for all decoders, so
 *    we just upsample when it is necessary.
 * \param imY
 *    The frame to be upsampled
 * \param block_y
 *    The row of the block, whose prediction we want to find
 * \param block_x
 *    The column of the block, whose prediction we want to track
 * \param mvhor
 *    Motion vector, horizontal part
 * \param mvver
 *    Motion vector, vertical part
 * \param out
 *    Output: The prediction for the block (block_y, block_x)
 *************************************************************************************
 */
void Get_Reference_Block(byte **imY, 
                         int block_y, 
                         int block_x, 
                         int mvhor, 
                         int mvver, 
                         byte **out)
{
  int i,j,y,x;

  y = block_y * BLOCK_SIZE * 4 + mvver;
  x = block_x * BLOCK_SIZE * 4 + mvhor;

  for (j=0; j<BLOCK_SIZE; j++)
    for (i=0; i<BLOCK_SIZE; i++)
      out[j][i] = Get_Reference_Pixel(imY, 
                  max(0,min(img->mvert, y+j*4)), 
                  max(0,min(img->mhor, x+i*4)));
}

/*! 
 *************************************************************************************
 * \brief
 *    Finds a pixel (y,x) of the upsampled reference frame
 * \note
 *    This is based on the function UnifiedOneForthPix, only it is modified to
 *    be used at the "many decoders in the encoder" RD optimization. In this case
 *    we dont want to keep full upsampled reference frames for all decoders, so
 *    we just upsample when it is necessary.
 *************************************************************************************
 */
byte Get_Reference_Pixel(byte **imY, int y_pos, int x_pos)
{

  int dx, x;
  int dy, y;
  int maxold_x,maxold_y;

  int result = 0, result1, result2;
  int pres_x;
  int pres_y; 

  int tmp_res[6];

  static const int COEF[6] = {
    1, -5, 20, 20, -5, 1
  };


  dx = x_pos&3;
  dy = y_pos&3;
  x_pos = (x_pos-dx)/4;
  y_pos = (y_pos-dy)/4;
  maxold_x = img->width-1;
  maxold_y = img->height-1;

  if (dx == 0 && dy == 0) { /* fullpel position */
    result = imY[max(0,min(maxold_y,y_pos))][max(0,min(maxold_x,x_pos))];
  }
  else if (dx == 3 && dy == 3) { /* funny position */
    result = (imY[max(0,min(maxold_y,y_pos))  ][max(0,min(maxold_x,x_pos))  ]+
              imY[max(0,min(maxold_y,y_pos))  ][max(0,min(maxold_x,x_pos+1))]+
              imY[max(0,min(maxold_y,y_pos+1))][max(0,min(maxold_x,x_pos+1))]+
              imY[max(0,min(maxold_y,y_pos+1))][max(0,min(maxold_x,x_pos))  ]+2)/4;
  }
  else { /* other positions */

    if (dy == 0) {

      pres_y = max(0,min(maxold_y,y_pos));
      for(x=-2;x<4;x++) {
        pres_x = max(0,min(maxold_x,x_pos+x));
        result += imY[pres_y][pres_x]*COEF[x+2];
      }

      result = max(0, min(255, (result+16)/32));