mot_est.c

H.263的压缩算法

  }
#endif

  if (use_4mv)
  {

    /* Center the 8x8 search around the 16x16 vector.  This is different
     * than in TMN5 where the 8x8 search is also a full search. The
     * reasons for this is: (i) it is faster, and (ii) it generally gives
     * better results because of a better OBMC filtering effect and less
     * bits spent for vectors, and (iii) if the Extended MV Range is used,
     * the search range around the motion vector predictor will be less
     * limited */

    xvec = MV_FRAME[0].x;
    yvec = MV_FRAME[0].y;

    if (!long_vectors || estimation_type == PB_PICTURE_ESTIMATION)
    {
      if (xvec > 15 - DEF_8X8_WIN)
      {
        xvec = 15 - DEF_8X8_WIN;
      }
      if (yvec > 15 - DEF_8X8_WIN)
      {
        yvec = 15 - DEF_8X8_WIN;
      }
      if (xvec < -15 + DEF_8X8_WIN)
      {
        xvec = -15 + DEF_8X8_WIN;
      }
      if (yvec < -15 + DEF_8X8_WIN)
      {
        yvec = -15 + DEF_8X8_WIN;
      }
    }
    adv_x_curr = x_curr + xvec;
    adv_y_curr = y_curr + yvec;

    sxy = DEF_8X8_WIN;

    adv_ilow = adv_x_curr - xlim;
    adv_ihigh = adv_x_curr + xlim;

    adv_jlow = adv_y_curr - ylim;
    adv_jhigh = adv_y_curr + ylim;

    adv_h_length = adv_ihigh - adv_ilow + 16;
    adv_v_length = adv_jhigh - adv_jlow + 16;

    adv_search_area = LoadArea (reference, adv_ilow, adv_jlow,
                                adv_h_length, adv_v_length, lx);

    for (block = 0; block < 4; block++)
    {
      ii = adv_search_area + (adv_x_curr - adv_ilow) + ((block & 1) << 3) +
        (adv_y_curr - adv_jlow + ((block & 2) << 2)) * adv_h_length;
      aa = act_block + ((block & 1) << 3) + ((block & 2) << 2) * 16;
      Min_FRAME[block + 1] = SAD_Block (ii, aa, adv_h_length, Min_FRAME[block + 1]);
      MV_FRAME[block + 1].x = MV_FRAME[0].x;
      MV_FRAME[block + 1].y = MV_FRAME[0].y;
    }

    /* Spiral search for full search motion estimation */
#ifdef FULLSEARCH
    for (l = 1; l <= sxy; l++) {
      i = adv_x_curr - l;
      j = adv_y_curr - l;
      for (k = 0; k < 8*l; k++) {
        if (i>=adv_ilow && i<=adv_ihigh && j>=adv_jlow && j<=adv_jhigh) {
          
          /* 8x8 integer pel MVs */
          for (block = 0; block < 4; block++) {
            ii = adv_search_area + (i-adv_ilow) + ((block&1)<<3) + 
              (j-adv_jlow + ((block&2)<<2) )*adv_h_length;
            aa = act_block + ((block&1)<<3) + ((block&2)<<2)*16;
            sad = SAD_Block(ii, aa, adv_h_length, Min_FRAME[block+1]);
            if (sad < Min_FRAME[block+1]) {
              MV_FRAME[block+1].x = i - x_curr;
              MV_FRAME[block+1].y = j - y_curr;
              Min_FRAME[block+1] = sad;
            }
          }
          
        }
        if      (k<2*l) i++;
        else if (k<4*l) j++;
        else if (k<6*l) i--;
        else            j--;
      }      
    }
#else
    /* Fast search motion estimation */
    for (block = 0; block < 4; block++)
    {
      i_min_now = adv_x_curr;
      j_min_now = adv_y_curr;

      distortion_0 = distortion_1 = distortion_2 = 65536;

      for (l = 1; l <= 2 * sxy; l++)
      {
        sad_layr = 65536;
        for (m = 0; m < 4; m++)
        {

          i = i_min_now + htp[m];
          j = j_min_now + vtp[m];

          if (i >= adv_ilow && i <= adv_ihigh && j >= adv_jlow && j <= adv_jhigh)
          {
            /* 8x8 integer pel MVs */
            ii = adv_search_area + (i - adv_ilow) + ((block & 1) << 3) +
              (j - adv_jlow + ((block & 2) << 2)) * adv_h_length;
            aa = act_block + ((block & 1) << 3) + ((block & 2) << 2) * 16;
            sad = SAD_Block (ii, aa, adv_h_length, sad_layr);
            if (sad < Min_FRAME[block + 1])
            {
              MV_FRAME[block + 1].x = i - x_curr;
              MV_FRAME[block + 1].y = j - y_curr;
              Min_FRAME[block + 1] = sad;
            }
            if (sad < sad_layr)
            {
              sad_layr = sad;
              i_min_next = i;
              j_min_next = j;
            }
          }
        }
      }

      i_min_now = i_min_next;
      j_min_now = j_min_next;

      distortion_2 = distortion_1;
      distortion_1 = distortion_0;
      distortion_0 = sad_layr;
      if (distortion_1 <= distortion_0 && distortion_2 <= distortion_0)
      {
        break;
      }
    }
#endif

  }
  i = x_curr / MB_SIZE + 1;
  j = y_curr / MB_SIZE + 1;

  if (!use_4mv)
  {
    if(!backward_pred)
    {
      MV[0][j][i]->x = MV_FRAME[0].x;
      MV[0][j][i]->y = MV_FRAME[0].y;
      MV[0][j][i]->min_error = Min_FRAME[0];
    }
    else
    {
      MV[5][j][i]->x = MV_FRAME[0].x;
      MV[5][j][i]->y = MV_FRAME[0].y;
      MV[5][j][i]->min_error = Min_FRAME[0];
    }
  } 
  else
  {
    for (k = 0; k < 5; k++)
    {
      MV[k][j][i]->x = MV_FRAME[k].x;
      MV[k][j][i]->y = MV_FRAME[k].y;
      MV[k][j][i]->min_error = Min_FRAME[k];
    }
  }

  free (act_block);
  free (search_area);
  if (use_4mv)
    free (adv_search_area);
  return;
}

/**********************************************************************
 *
 *	Name:        FindHalfPel
 *	Description:	Find the optimal half pel prediction
 *
 *	Input:        position, vector, array with current data
 *        pointer to previous interpolated luminance,
 *
 *	Returns:
 *
 *	Date: 930126        Author: [e-mail]
 *            950208    Mod: [e-mail]
 *
 ***********************************************************************/


void FindHalfPel (int x, int y, MotionVector * fr, unsigned char *prev,
                  int *curr, int bs, int comp)
{
  int i, m, n;
  int half_pel;
  int start_x, start_y, stop_x, stop_y, new_x, new_y, lx;
  int min_pos;
  int AE, AE_min;
  Point search[9];

  start_x = -1;
  stop_x = 1;
  start_y = -1;
  stop_y = 1;

  new_x = x + fr->x;
  new_y = y + fr->y;

  new_x += ((comp & 1) << 3);
  new_y += ((comp & 2) << 2);

  lx = (mv_outside_frame ? pels + (long_vectors ? 64 : 32) : pels);

  /* Make sure that no addressing is outside the frame */
  if (!mv_outside_frame)
  {
    if ((new_x) <= 0)
      start_x = 0;
    if ((new_y) <= 0)
      start_y = 0;
    if ((new_x) >= (pels - bs))
      stop_x = 0;
    if ((new_y) >= (lines - bs))
      stop_y = 0;
  }
  search[0].x = 0;
  search[0].y = 0;
  search[1].x = start_x;
  search[1].y = start_y;        /* 1 2 3   */
  search[2].x = 0;
  search[2].y = start_y;        /* 4 0 5   */
  search[3].x = stop_x;
  search[3].y = start_y;        /* 6 7 8   */
  search[4].x = start_x;
  search[4].y = 0;
  search[5].x = stop_x;
  search[5].y = 0;
  search[6].x = start_x;
  search[6].y = stop_y;
  search[7].x = 0;
  search[7].y = stop_y;
  search[8].x = stop_x;
  search[8].y = stop_y;

  AE_min = INT_MAX;
  min_pos = 0;
  for (i = 0; i < 9; i++)
  {
    AE = 0;
    for (n = 0; n < bs; n++)
    {
      for (m = 0; m < bs; m++)
      {
        /* Find absolute error */
        half_pel = *(prev + 2 * new_x + 2 * m + search[i].x +
                     (2 * new_y + 2 * n + search[i].y) * lx * 2);
        AE += abs (half_pel - *(curr + m + n * 16));
      }
    }
    /* if (i == 0 && fr->x == 0 && fr->y == 0 && bs == 16) AE -=
     * PREF_NULL_VEC; */
    if (AE < AE_min)
    {
      AE_min = AE;
      min_pos = i;
    }
  }

  /* Store optimal values */
  fr->min_error = AE_min;
  fr->x_half = search[min_pos].x;
  fr->y_half = search[min_pos].y;

  return;
}


/**********************************************************************
 *
 *	Name:        ChooseMode
 *	Description:    chooses coding mode
 *
 *	Input:	        pointer to original fram, min_error from
 *                      integer pel search, DQUANT
 *	Returns:        1 for Inter, 0 for Intra
 *
 *	Date: 941130	Author: [e-mail]
 *
 ***********************************************************************/

int ChooseMode (unsigned char *curr, int x_pos, int y_pos, int min_SAD)
{
  int i, j;
  int MB_mean = 0, A = 0;
  int y_off;

  for (j = 0; j < MB_SIZE; j++)
  {
    y_off = (y_pos + j) * pels;
    for (i = 0; i < MB_SIZE; i++)
    {
      MB_mean += *(curr + x_pos + i + y_off);
    }
  }
  MB_mean /= (MB_SIZE * MB_SIZE);
  for (j = 0; j < MB_SIZE; j++)
  {
    y_off = (y_pos + j) * pels;
    for (i = 0; i < MB_SIZE; i++)
    {
      A += abs (*(curr + x_pos + i + y_off) - MB_mean);
    }
  }

  if (A < (min_SAD - 500))
    return MODE_INTRA;
  else
    return MODE_INTER;
}

int ModifyMode (int Mode, int dquant, int EPTYPE)
{

  if (Mode == MODE_INTRA)
  {
    if (dquant != 0)
      return MODE_INTRA_Q;
    else
      return MODE_INTRA;
  } else if (Mode == MODE_INTER)
  {
    if (dquant != 0)
      return MODE_INTER_Q;
    else
      return MODE_INTER;
  } else if (Mode == MODE_INTER4V)
  {
    if (dquant != 0 && EPTYPE)
      return MODE_INTER4V_Q;
    else
      return MODE_INTER4V;
  } else
    return Mode;
}


void InitializeMV(MotionVector *MV[7][MBR+1][MBC+2])
{
  int i,j,k;

  for (j=0; j<(lines>>4)+1; ++j)
  {
    for (i=0; i<(pels>>4)+2; ++i)
    {
      for (k=0; k<7; ++k)
      {
        MV[k][j][i] = (MotionVector *)calloc(1,sizeof(MotionVector));
      }
    }
  }
}