intra_pred.c

H.263的压缩算法

        (A[0][i] == 1024 && B[0][i] == 1024) ? 1024 :
        (A[0][i] == 1024) ? B[0][i] :
        (B[0][i] == 1024) ? A[0][i] : ((A[0][i] + B[0][i]) / 2);

      break;
    case INTRA_MODE_VERT_AC:
      for (j = 0; j < 8; j++)
      {
        pcoeff[j + i * 64] -= A[j][i];
      }
      break;
    case INTRA_MODE_HORI_AC:
      for (j = 0; j < 8; j++)
      {
        pcoeff[j * 8 + i * 64] -= B[j][i];
      }
      break;
    default:
      printf ("Error in Prediction in Advanced Intra Coding\n");
      exit (-1);
      break;
  }

#ifdef PRINTBLOCKS
  printf ("MB: %2i  Block: %1i\n", xpos + ypos * pels / MB_SIZE, i);

  printf ("pcoeff: \n");
  for (j = 0; j < 8; j++)
  {
    printf ("%4i%4i%4i%4i%4i%4i%4i%4i\n", pcoeff[j * 8 + i * 64], pcoeff[j * 8 + 1 + i * 64], pcoeff[j * 8 + 2 + i * 64], pcoeff[j * 8 + 3 + i * 64], pcoeff[j * 8 + 4 + i * 64], pcoeff[j * 8 + 5 + i * 64], pcoeff[j * 8 + 6 + i * 64], pcoeff[j * 8 + 7 + i * 64]);
  }

#endif

  return;
}

/**********************************************************************
 *
 *	Name:           fill_null, fill_A and fill_B
 *	Description:    Fill values in predictor coefficients
 *                      Functions used in advanced intra coding mode
 *
 *	Input:	        predictor qcoefficients
 *	Side effects:
 *
 *      Return:
 *
 *	Date:970717     Guy Cote <[e-mail]>
 *
 ***********************************************************************/


void fill_null (int pred[][6], int i)
{
  int j;

  pred[0][i] = 1024;

  for (j = 1; j < 8; j++)
  {
    pred[j][i] = 0;
  }
}

void fill_A (int pred[][6], int *store_rcoeff, int xpos, int ypos, int block, int i)
{
  /* Fill first row of block at MB xpos, ypos, in pred[][i] */
  int j;

  for (j = 0; j < 8; j++)
  {
    pred[j][i] = *(store_rcoeff + (ypos * pels / MB_SIZE + xpos) * 384 + block * 64 + j);
  }
}

void fill_B (int pred[][6], int *store_rcoeff, int xpos, int ypos, int block, int i)
{
  /* Fill first column of block at MB xpos, ypos, in pred[][i] */
  int j;

  for (j = 0; j < 8; j++)
  {
    pred[j][i] = *(store_rcoeff + (ypos * pels / MB_SIZE + xpos) * 384 + block * 64 + j * 8);
  }
}


/**********************************************************************
 *
 *	Name:           Intra_AC_DC_Decode
 *	Description:    Intra Prediction in Advanced Intra Coding
 *
 *	Input:	        store_rcoeff, Intra_AC_DC, position of MB, store_QP
 *
 *	Side effects:   change qcoeff to predicted qcoeff
 *
 *      Return:
 *
 *	Date:970717     Guy Cote <[e-mail]>
 *
 ***********************************************************************/


void Intra_AC_DC_Decode (int *rcoeff, int *store_rcoeff, int INTRA_AC_DC, int xpos, int ypos, int newgob, int i)
{

  int A[8][6], B[8][6];
  int j, k, tempDC;


  if (xpos == 0 && ypos == 0)
  {                             
    /* top left corner */
    (i == 2 || i == 3) ? fill_A (A, store_rcoeff, xpos, ypos, i - 2, i) : fill_null (A, i);
    (i == 1 || i == 3) ? fill_B (B, store_rcoeff, xpos, ypos, i - 1, i) : fill_null (B, i);
  } else
  {                             /* left border of picture */
    if (xpos == 0)
    {                           /* left edge of the picture */
      (i == 2 || i == 3) ? fill_A (A, store_rcoeff, xpos, ypos, i - 2, i) :
      ((i == 0 || i == 1) && !(newgob)) ? fill_A (A, store_rcoeff, xpos, ypos - 1, i + 2, i) :
      ((i == 4 || i == 5) && !(newgob)) ? fill_A (A, store_rcoeff, xpos, ypos - 1, i, i) : fill_null (A, i);
      (i == 1 || i == 3) ? fill_B (B, store_rcoeff, xpos, ypos, i - 1, i) : fill_null (B, i);

    } else
    {
      if (ypos == 0)
      {                         /* top border of picture */
        (i == 2 || i == 3) ? fill_A (A, store_rcoeff, xpos, ypos, i - 2, i) : fill_null (A, i);
        (i == 4 || i == 5) ? fill_B (B, store_rcoeff, xpos - 1, ypos, i, i) :
        (i == 1 || i == 3) ? fill_B (B, store_rcoeff, xpos, ypos, i - 1, i) :
        fill_B (B, store_rcoeff, xpos - 1, ypos, i + 1, i);
      } else
      {                         
        /* anywhere else in the picture, do not
         * cross GOB boundary */
        (i == 2 || i == 3) ? fill_A (A, store_rcoeff, xpos, ypos, i - 2, i) :
        ((i == 0 || i == 1) && !(newgob)) ? fill_A (A, store_rcoeff, xpos, ypos - 1, i + 2, i) :
        ((i == 4 || i == 5) && !(newgob)) ? fill_A (A, store_rcoeff, xpos, ypos - 1, i, i) : fill_null (A, i);

        (i == 4 || i == 5) ? fill_B (B, store_rcoeff, xpos - 1, ypos, i, i) :
        (i == 1 || i == 3) ? fill_B (B, store_rcoeff, xpos, ypos, i - 1, i) :
        fill_B (B, store_rcoeff, xpos - 1, ypos, i + 1, i);
      }
    }
  }

  switch (INTRA_AC_DC)
  {
    case INTRA_MODE_DC:
      /* It is OK to use 1024 to check the DC direction since the DC *
       * reconstructed coefficient will always be odd                */
      tempDC = rcoeff[i * 64]
        + ((A[0][i] == 1024 && B[0][i] == 1024) ? 1024 :
           (A[0][i] == 1024) ? B[0][i] :
           (B[0][i] == 1024) ? A[0][i] : (A[0][i] + B[0][i]) / 2);
      for (j = 0; j < 8; j++)
        for (k = 0; k < 8; k++)
          rcoeff[i * 64 + j * 8 + k] = clipAC (rcoeff[i * 64 + j * 8 + k]);
      rcoeff[i * 64] = oddifyclipDC (tempDC);
      break;

    case INTRA_MODE_VERT_AC:
      tempDC = rcoeff[i * 64] + A[0][i];
      for (j = 1; j < 8; j++)
      {
        rcoeff[i * 64 + j] = clipAC (rcoeff[i * 64 + j] + A[j][i]);
      }
      for (j = 1; j < 8; j++)
        for (k = 0; k < 8; k++)
          rcoeff[i * 64 + j * 8 + k] = clipAC (rcoeff[i * 64 + j * 8 + k]);
      rcoeff[i * 64] = oddifyclipDC (tempDC);
      break;
    case INTRA_MODE_HORI_AC:
      tempDC = rcoeff[i * 64] + B[0][i];
      for (j = 1; j < 8; j++)
        rcoeff[i * 64 + j * 8] = clipAC (rcoeff[i * 64 + j * 8] + B[j][i]);
      for (j = 0; j < 8; j++)
        for (k = 1; k < 8; k++)
          rcoeff[i * 64 + j * 8 + k] = clipAC (rcoeff[i * 64 + j * 8 + k]);
      rcoeff[i * 64] = oddifyclipDC (tempDC);
      break;
    default:
      printf ("Error in Prediction in Advanced Intra Coding\n");
      exit (-1);
      break;
  }
  
  /* store the  reconstructed DCT coefficients */
  memcpy ((void *) (store_rcoeff + i * 64 + (xpos + ypos * pels / MB_SIZE) * 384), (void *) (rcoeff + i * 64), sizeof (int) * 64);



#ifdef PRINTBLOCKS
  printf ("MB: %2i  Block: %1i\n", xpos + ypos * pels / MB_SIZE, i);

  printf ("rcoeff: \n");
  for (j = 0; j < 8; j++)
  {
    printf ("%4i%4i%4i%4i%4i%4i%4i%4i\n", rcoeff[j * 8 + i * 64], rcoeff[j * 8 + 1 + i * 64], rcoeff[j * 8 + 2 + i * 64], rcoeff[j * 8 + 3 + i * 64], rcoeff[j * 8 + 4 + i * 64], rcoeff[j * 8 + 5 + i * 64], rcoeff[j * 8 + 6 + i * 64], rcoeff[j * 8 + 7 + i * 64]);
  }
#endif
  return;
}

/**********************************************************************
 *
 *	Name:           oddifyclipDC, clipAC and clipDC
 *	Description:    Fill values in predictor coefficients
 *                      Functions used in advanced intra coding mode
 *
 *	Input:	        predictor qcoefficients
 *	Side effects:
 *
 *      Return:
 *
 *	Date:970717     Guy Cote <[e-mail]>
 *
 ***********************************************************************/


int oddifyclipDC (int x)
{

  int result;

  (x % 2) ? (result = clipDC (x)) : (result = clipDC (x + 1));
  return result;
}
int clipAC (int x)
{
  int clipped;

  if (x > 2047)
    clipped = 2047;
  else if (x < -2048)
    clipped = -2048;
  else
    clipped = x;
  return clipped;

}
int clipDC (int x)
{
  int clipped;
  if (x > 2047)
    clipped = 2047;
  else if (x < 0)
    clipped = 0;
  else
    clipped = x;
  return clipped;
}