predict.c

avi2mpg1_src 中包含了mpeg1编码的源程序

/* predict.c, 运动补偿预测*/


#include <stdio.h>
#include "global.h"

/* 函数声明*/
static void predict_mb(
  unsigned char *oldref[], unsigned char *newref[], unsigned char *cur[],
  int lx, int bx, int by, int pict_type, int pict_struct, int mb_type,
  int motion_type, int secondfield,
  int PMV[2][2][2], int mv_field_sel[2][2], int dmvector[2]);

static void pred(unsigned char *src[], int sfield,
  unsigned char *dst[], int dfield,
  int lx, int w, int h, int x, int y, int dx, int dy, int addflag);

static void pred_comp(unsigned char *src, unsigned char *dst,
  int lx, int w, int h, int x, int y, int dx, int dy, int addflag);

static void calc_DMV(int DMV[][2], int *dmvector, int mvx,
  int mvy);

static void clearblock(unsigned char *cur[], int i0, int j0);

static short PACKED_0[4] = { 0, 0, 0, 0 };
static short PACKED_1[4] = { 1, 1, 1, 1 };
static short PACKED_2[4] = { 2, 2, 2, 2 };


/* 为一个完整的图像形成预测
 *
 * reff: 前向预测参考帧
 * refb: 后向预测参考帧
 * cur:  目标帧
 * secondfield: 预测帧的第二场
 * mbi:  宏块信息
 *
 
 */

void predict(reff,refb,cur,secondfield,mbi)
unsigned char *reff[],*refb[],*cur[3];
int secondfield;
struct mbinfo *mbi;
{
  int i, j, k;

  k = 0;

  for (j=0; j<height2; j+=16)
    for (i=0; i<width; i+=16)
    {
      predict_mb(reff,refb,cur,width,i,j,pict_type,pict_struct,
                 mbi[k].mb_type,mbi[k].motion_type,secondfield,
                 mbi[k].MV,mbi[k].mv_field_sel,mbi[k].dmvector);

      k++;
    }
}

/* 为一个宏块形成预测
 *
 * oldref: 前向预测的参考帧
 * newref: 后向预测的参考帧
 * cur:    目标帧
 * lx:     帧的宽度
 * bx,by:  要预测的宏块的图像 (场或帧) 坐标
 * pict_type: I, P 或 B
 * pict_struct: FRAME_PICTURE, TOP_FIELD, BOTTOM_FIELD
 * mb_type:     MB_FORWARD, MB_BACKWARD, MB_INTRA
 * motion_type: MC_FRAME, MC_FIELD, MC_16X8, MC_DMV
 * secondfield: 预测一帧的第二场
 * PMV[2][2][2]: 运动向量
 * mv_field_sel[2][2]: 运动向量场选择
 * dmvector: 差分运动向量
 *
 
 */

static void predict_mb(oldref,newref,cur,lx,bx,by,pict_type,pict_struct,
  mb_type,motion_type,secondfield,PMV,mv_field_sel,dmvector)
unsigned char *oldref[],*newref[],*cur[];
int lx;
int bx,by;
int pict_type;
int pict_struct;
int mb_type;
int motion_type;
int secondfield;
int PMV[2][2][2], mv_field_sel[2][2], dmvector[2];
{
  int addflag, currentfield;
  unsigned char **predframe;
  int DMV[2][2];

  if (mb_type&MB_INTRA)
  {
    clearblock(cur,bx,by);
    return;
  }

  addflag = 0; /* first prediction is stored, second is added and averaged */

  if ((mb_type & MB_FORWARD) || (pict_type==P_TYPE))
  {
    /* forward prediction, including zero MV in P pictures */

    if (pict_struct==FRAME_PICTURE)
    {
      /* frame picture */

      if ((motion_type==MC_FRAME) || !(mb_type & MB_FORWARD))
      {
        /* frame-based prediction in frame picture */
        pred(oldref,0,cur,0,
          lx,16,16,bx,by,PMV[0][0][0],PMV[0][0][1],0);
      }
      else if (motion_type==MC_FIELD)
      {
       

        /* top field prediction */
        pred(oldref,mv_field_sel[0][0],cur,0,
          lx<<1,16,8,bx,by>>1,PMV[0][0][0],PMV[0][0][1]>>1,0);

        /* bottom field prediction */
        pred(oldref,mv_field_sel[1][0],cur,1,
          lx<<1,16,8,bx,by>>1,PMV[1][0][0],PMV[1][0][1]>>1,0);
      }
      else if (motion_type==MC_DMV)
      {

        /* calculate derived motion vectors */
        calc_DMV(DMV,dmvector,PMV[0][0][0],PMV[0][0][1]>>1);

        /* predict top field from top field */
        pred(oldref,0,cur,0,
          lx<<1,16,8,bx,by>>1,PMV[0][0][0],PMV[0][0][1]>>1,0);

        /* predict bottom field from bottom field */
        pred(oldref,1,cur,1,
          lx<<1,16,8,bx,by>>1,PMV[0][0][0],PMV[0][0][1]>>1,0);

        /* predict and add to top field from bottom field */
        pred(oldref,1,cur,0,
          lx<<1,16,8,bx,by>>1,DMV[0][0],DMV[0][1],1);

        /* predict and add to bottom field from top field */
        pred(oldref,0,cur,1,
          lx<<1,16,8,bx,by>>1,DMV[1][0],DMV[1][1],1);
      }
      else
      {
        /* invalid motion_type in frame picture */
        if (!quiet)
          fprintf(stderr,"invalid motion_type\n");
      }
    }
    else /* TOP_FIELD or BOTTOM_FIELD */
    {
      /* field picture */

      currentfield = (pict_struct==BOTTOM_FIELD);

      if ((pict_type==P_TYPE) && secondfield
          && (currentfield!=mv_field_sel[0][0]))
        predframe = newref; /* same frame */
      else
        predframe = oldref; /* previous frame */

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

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

        if ((pict_type==P_TYPE) && secondfield
            && (currentfield!=mv_field_sel[1][0]))
          predframe = newref; /* same frame */
        else
          predframe = oldref; /* previous frame */

        /* lower half */
        pred(predframe,mv_field_sel[1][0],cur,currentfield,
          lx<<1,16,8,bx,by+8,PMV[1][0][0],PMV[1][0][1],0);
      }
      else if (motion_type==MC_DMV)
      {
        
        /* determine which frame to use for prediction */
        if (secondfield)
          predframe = newref; /* same frame */
        else
          predframe = oldref; /* previous frame */

        /* calculate derived motion vectors */
        calc_DMV(DMV,dmvector,PMV[0][0][0],PMV[0][0][1]);

        /* predict from field of same parity */
        pred(oldref,currentfield,cur,currentfield,
          lx<<1,16,16,bx,by,PMV[0][0][0],PMV[0][0][1],0);

        /* predict from field of opposite parity */
        pred(predframe,!currentfield,cur,currentfield,
          lx<<1,16,16,bx,by,DMV[0][0],DMV[0][1],1);
      }
      else
      {
        if (!quiet)
          fprintf(stderr,"invalid motion_type\n");
      }
    }
    addflag = 1; 
  }

  if (mb_type & MB_BACKWARD)
  {
    /* backward prediction */

    if (pict_struct==FRAME_PICTURE)
    {
      /* frame picture */

      if (motion_type==MC_FRAME)
      {
        /* frame-based prediction in frame picture */
        pred(newref,0,cur,0,
          lx,16,16,bx,by,PMV[0][1][0],PMV[0][1][1],addflag);
      }
      else
      {
        

        /* top field prediction */
        pred(newref,mv_field_sel[0][1],cur,0,
          lx<<1,16,8,bx,by>>1,PMV[0][1][0],PMV[0][1][1]>>1,addflag);

        /* bottom field prediction */
        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");
      }
    }
  }
}

/* 预测矩形块
 *
 * src:     源帧(Y,U,V)
 * sfield:  源场选择(0: 帧或上半场, 1: 下半场)
 * dst:     目标帧(Y,U,V)
 * dfield:  目标场选择
 *
 * 下面的数值是亮度图像的参数
 * lx:      相邻像素的垂直距离
 * w,h:     块的宽度和高度
 * x,y:     目标块的坐标
 * dx,dy:   半像素运动向量
 * addflag: 存储或加预测
 */
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);
  }
}

/* 低等级预测
 *
 * src:     源帧(Y,U,V)
 * dst:     目标帧(Y,U,V)
 *
 * lx:      相邻像素的垂直距离
 * w,h:     块的宽度和高度
 * x,y:     目标块的坐标
 * dx,dy:   半像素运动向量
 * addflag: 存储或加预测