predict.c

MPEG2视频编解码算法方面的源代码(包括编码和解码)

        pred(newref,mv_field_sel[1][1],cur,1,
          lx<<1,16,8,bx,by>>1,PMV[1][1][0],PMV[1][1][1]>>1,addflag);
      }
    }
    else /* TOP_FIELD or BOTTOM_FIELD */
    {
      /* field picture */

      currentfield = (pict_struct==BOTTOM_FIELD);

      if (motion_type==MC_FIELD)
      {
        /* field-based prediction in field picture */
        pred(newref,mv_field_sel[0][1],cur,currentfield,
          lx<<1,16,16,bx,by,PMV[0][1][0],PMV[0][1][1],addflag);
      }
      else if (motion_type==MC_16X8)
      {
        /* 16 x 8 motion compensation in field picture */

        /* upper half */
        pred(newref,mv_field_sel[0][1],cur,currentfield,
          lx<<1,16,8,bx,by,PMV[0][1][0],PMV[0][1][1],addflag);

        /* lower half */
        pred(newref,mv_field_sel[1][1],cur,currentfield,
          lx<<1,16,8,bx,by+8,PMV[1][1][0],PMV[1][1][1],addflag);
      }
      else
      {
        /* invalid motion_type in field picture */
        if (!quiet)
          fprintf(stderr,"invalid motion_type\n");
      }
    }
  }
}

/* predict a rectangular block (all three components)
 *
 * src:     source frame (Y,U,V)
 * sfield:  source field select (0: frame or top field, 1: bottom field)
 * dst:     destination frame (Y,U,V)
 * dfield:  destination field select (0: frame or top field, 1: bottom field)
 *
 * the following values are in luminance picture (frame or field) dimensions
 * lx:      distance of vertically adjacent pels (selects frame or field pred.)
 * w,h:     width and height of block (only 16x16 or 16x8 are used)
 * x,y:     coordinates of destination block
 * dx,dy:   half pel motion vector
 * addflag: store or add (= average) prediction
 */
static void pred(src,sfield,dst,dfield,lx,w,h,x,y,dx,dy,addflag)
unsigned char *src[];
int sfield;
unsigned char *dst[];
int dfield;
int lx;
int w, h;
int x, y;
int dx, dy;
int addflag;
{
  int cc;

  for (cc=0; cc<3; cc++)
  {
    if (cc==1)
    {
      /* scale for color components */
      if (chroma_format==CHROMA420)
      {
        /* vertical */
        h >>= 1; y >>= 1; dy /= 2;
      }
      if (chroma_format!=CHROMA444)
      {
        /* horizontal */
        w >>= 1; x >>= 1; dx /= 2;
        lx >>= 1;
      }
    }
    pred_comp(src[cc]+(sfield?lx>>1:0),dst[cc]+(dfield?lx>>1:0),
      lx,w,h,x,y,dx,dy,addflag);
  }
}

/* low level prediction routine
 *
 * src:     prediction source
 * dst:     prediction destination
 * lx:      line width (for both src and dst)
 * x,y:     destination coordinates
 * dx,dy:   half pel motion vector
 * w,h:     size of prediction block
 * addflag: store or add prediction
 */

static void pred_comp(src,dst,lx,w,h,x,y,dx,dy,addflag)
unsigned char *src;
unsigned char *dst;
int lx;
int w, h;
int x, y;
int dx, dy;
int addflag;
{
  int xint, xh, yint, yh;
  int i, j;
  unsigned char *s, *d;

  /* half pel scaling */
  xint = dx>>1; /* integer part */
  xh = dx & 1;  /* half pel flag */
  yint = dy>>1;
  yh = dy & 1;

  /* origins */
  s = src + lx*(y+yint) + (x+xint); /* motion vector */
  d = dst + lx*y + x;

  if (!xh && !yh)
    if (addflag)
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (unsigned int)(d[i]+s[i]+1)>>1;
        s+= lx;
        d+= lx;
      }
    else
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = s[i];
        s+= lx;
        d+= lx;
      }
  else if (!xh && yh)
    if (addflag)
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (d[i] + ((unsigned int)(s[i]+s[i+lx]+1)>>1)+1)>>1;
        s+= lx;
        d+= lx;
      }
    else
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (unsigned int)(s[i]+s[i+lx]+1)>>1;
        s+= lx;
        d+= lx;
      }
  else if (xh && !yh)
    if (addflag)
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (d[i] + ((unsigned int)(s[i]+s[i+1]+1)>>1)+1)>>1;
        s+= lx;
        d+= lx;
      }
    else
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (unsigned int)(s[i]+s[i+1]+1)>>1;
        s+= lx;
        d+= lx;
      }
  else /* if (xh && yh) */
    if (addflag)
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (d[i] + ((unsigned int)(s[i]+s[i+1]+s[i+lx]+s[i+lx+1]+2)>>2)+1)>>1;
        s+= lx;
        d+= lx;
      }
    else
      for (j=0; j<h; j++)
      {
        for (i=0; i<w; i++)
          d[i] = (unsigned int)(s[i]+s[i+1]+s[i+lx]+s[i+lx+1]+2)>>2;
        s+= lx;
        d+= lx;
      }
}


/* calculate derived motion vectors (DMV) for dual prime prediction
 * dmvector[2]: differential motion vectors (-1,0,+1)
 * mvx,mvy: motion vector (for same parity)
 *
 * DMV[2][2]: derived motion vectors (for opposite parity)
 *
 * uses global variables pict_struct and topfirst
 *
 * Notes:
 *  - all vectors are in field coordinates (even for frame pictures)
 */

static void calc_DMV(DMV,dmvector,mvx,mvy)
int DMV[][2];
int *dmvector;
int mvx, mvy;
{
  if (pict_struct==FRAME_PICTURE)
  {
    if (topfirst)
    {
      /* vector for prediction of top field from bottom field */
      DMV[0][0] = ((mvx  +(mvx>0))>>1) + dmvector[0];
      DMV[0][1] = ((mvy  +(mvy>0))>>1) + dmvector[1] - 1;

      /* vector for prediction of bottom field from top field */
      DMV[1][0] = ((3*mvx+(mvx>0))>>1) + dmvector[0];
      DMV[1][1] = ((3*mvy+(mvy>0))>>1) + dmvector[1] + 1;
    }
    else
    {
      /* vector for prediction of top field from bottom field */
      DMV[0][0] = ((3*mvx+(mvx>0))>>1) + dmvector[0];
      DMV[0][1] = ((3*mvy+(mvy>0))>>1) + dmvector[1] - 1;

      /* vector for prediction of bottom field from top field */
      DMV[1][0] = ((mvx  +(mvx>0))>>1) + dmvector[0];
      DMV[1][1] = ((mvy  +(mvy>0))>>1) + dmvector[1] + 1;
    }
  }
  else
  {
    /* vector for prediction from field of opposite 'parity' */
    DMV[0][0] = ((mvx+(mvx>0))>>1) + dmvector[0];
    DMV[0][1] = ((mvy+(mvy>0))>>1) + dmvector[1];

    /* correct for vertical field shift */
    if (pict_struct==TOP_FIELD)
      DMV[0][1]--;
    else
      DMV[0][1]++;
  }
}

static void clearblock(cur,i0,j0)
unsigned char *cur[];
int i0, j0;
{
  int i, j, w, h;
  unsigned char *p;

  p = cur[0] + ((pict_struct==BOTTOM_FIELD) ? width : 0) + i0 + width2*j0;

  for (j=0; j<16; j++)
  {
    for (i=0; i<16; i++)
      p[i] = 128;
    p+= width2;
  }

  w = h = 16;

  if (chroma_format!=CHROMA444)
  {
    i0>>=1; w>>=1;
  }

  if (chroma_format==CHROMA420)
  {
    j0>>=1; h>>=1;
  }

  p = cur[1] + ((pict_struct==BOTTOM_FIELD) ? chrom_width : 0) + i0
             + chrom_width2*j0;

  for (j=0; j<h; j++)
  {
    for (i=0; i<w; i++)
      p[i] = 128;
    p+= chrom_width2;
  }

  p = cur[2] + ((pict_struct==BOTTOM_FIELD) ? chrom_width : 0) + i0
             + chrom_width2*j0;

  for (j=0; j<h; j++)
  {
    for (i=0; i<w; i++)
      p[i] = 128;
    p+= chrom_width2;
  }
}