*curref：當(dāng)前的重建圖像幀（用來根據(jù)第一個場預(yù)測第二個場）
 *sxf，syf：前向搜索窗口
 *sxb，syb：后向搜索窗口
 *mbi：指向宏塊信息結(jié)構(gòu)體的指針
 *secondfield：指示一幀圖像的第二個場
 *ipflag：指示當(dāng)前P圖像幀是由I圖像幀所預(yù)測產(chǎn)生的

 *輸出結(jié)果mbi->
 *mb_type: 0, MB_INTRA, MB_FORWARD, MB_BACKWARD, MB_FORWARD|MB_BACKWARD
 *MV[][][]: 運動向量 (場格式)
 *mv_field_sel: 頂部/底部場
 *motion_type: MC_FIELD, MC_16X8
 */static void field_ME(oldorg,neworg,oldref,newref,cur,curref,i,j,  sxf,syf,sxb,syb,mbi,secondfield,ipflag)unsigned char *oldorg,*neworg,*oldref,*newref,*cur,*curref;int i,j,sxf,syf,sxb,syb;struct mbinfo *mbi;int secondfield,ipflag;{  int w2;  unsigned char *mb, *toporg, *topref, *botorg, *botref;  int var,vmc,v0,dmc,dmcfieldi,dmc8i;  int imin,jmin,imin8u,jmin8u,imin8l,jmin8l,dmcfield,dmc8,sel,sel8u,sel8l;  int iminf,jminf,imin8uf,jmin8uf,imin8lf,jmin8lf,dmcfieldf,dmc8f,self,sel8uf,sel8lf;  int iminr,jminr,imin8ur,jmin8ur,imin8lr,jmin8lr,dmcfieldr,dmc8r,selr,sel8ur,sel8lr;  int imins,jmins,ds,imindmv,jmindmv,vmc_dp,dmc_dp;  w2 = width<<1;  mb = cur + i + w2*j;  if (pict_struct==BOTTOM_FIELD)    mb += width;  var = variance(mb,w2);  if (pict_type==I_TYPE)    mbi->mb_type = MB_INTRA;  else if (pict_type==P_TYPE)  {    toporg = oldorg;    topref = oldref;    botorg = oldorg + width;    botref = oldref + width;    if (secondfield)    {            if (pict_struct==TOP_FIELD)      {                botorg = cur + width;        botref = curref + width;      }      else      {                toporg = cur;        topref = curref;      }    }    field_estimate(toporg,topref,botorg,botref,mb,i,j,sxf,syf,ipflag,                   &imin,&jmin,&imin8u,&jmin8u,&imin8l,&jmin8l,                   &dmcfield,&dmc8,&sel,&sel8u,&sel8l,&imins,&jmins,&ds);    if (M==1 && !ipflag)        dpfield_estimate(topref,botref,mb,i,j,imins,jmins,&imindmv,&jmindmv,        &dmc_dp,&vmc_dp);        if (M==1 && !ipflag && dmc_dp<dmc8 && dmc_dp<dmcfield)    {            mbi->motion_type = MC_DMV;      dmc = dmc_dp;           vmc = vmc_dp;         }    else if (dmc8<dmcfield)    {       /* 16x8 預(yù)測 */      mbi->motion_type = MC_16X8;      /* 上半部分宏塊*/      vmc = dist2((sel8u?botref:topref) + (imin8u>>1) + w2*(jmin8u>>1),                  mb,w2,imin8u&1,jmin8u&1,8);      /* lower half block */      vmc+= dist2((sel8l?botref:topref) + (imin8l>>1) + w2*(jmin8l>>1),                  mb+8*w2,w2,imin8l&1,jmin8l&1,8);    }    else    {      /* 下半部分宏塊 */      mbi->motion_type = MC_FIELD;      vmc = dist2((sel?botref:topref) + (imin>>1) + w2*(jmin>>1),                  mb,w2,imin&1,jmin&1,16);    }    /* 選擇幀內(nèi)編碼還是非幀內(nèi)編碼*/    if (vmc>var && vmc>=9*256)      mbi->mb_type = MB_INTRA;    else    {            if (!ipflag)        v0 = dist2(((pict_struct==BOTTOM_FIELD)?botref:topref) + i + w2*j,                   mb,w2,0,0,16);      if (ipflag || (4*v0>5*vmc && v0>=9*256))      {        var = vmc;        mbi->mb_type = MB_FORWARD;        if (mbi->motion_type==MC_FIELD)        {          mbi->MV[0][0][0] = imin - (i<<1);          mbi->MV[0][0][1] = jmin - (j<<1);          mbi->mv_field_sel[0][0] = sel;        }        else if (mbi->motion_type==MC_DMV)        {                    mbi->MV[0][0][0] = imins - (i<<1);          mbi->MV[0][0][1] = jmins - (j<<1);                   mbi->dmvector[0] = imindmv;          mbi->dmvector[1] = jmindmv;        }        else        {          mbi->MV[0][0][0] = imin8u - (i<<1);          mbi->MV[0][0][1] = jmin8u - (j<<1);          mbi->MV[1][0][0] = imin8l - (i<<1);          mbi->MV[1][0][1] = jmin8l - ((j+8)<<1);          mbi->mv_field_sel[0][0] = sel8u;          mbi->mv_field_sel[1][0] = sel8l;        }      }      else      {                var = v0;        mbi->mb_type = 0;        mbi->motion_type = MC_FIELD;        mbi->MV[0][0][0] = 0;        mbi->MV[0][0][1] = 0;        mbi->mv_field_sel[0][0] = (pict_struct==BOTTOM_FIELD);      }    }  }  else /* 如果為B幀圖像*/  {    /* 前向預(yù)測*/    field_estimate(oldorg,oldref,oldorg+width,oldref+width,mb,                   i,j,sxf,syf,0,                   &iminf,&jminf,&imin8uf,&jmin8uf,&imin8lf,&jmin8lf,                   &dmcfieldf,&dmc8f,&self,&sel8uf,&sel8lf,&imins,&jmins,&ds);     /*后向預(yù)測*/    field_estimate(neworg,newref,neworg+width,newref+width,mb,                   i,j,sxb,syb,0,                   &iminr,&jminr,&imin8ur,&jmin8ur,&imin8lr,&jmin8lr,                   &dmcfieldr,&dmc8r,&selr,&sel8ur,&sel8lr,&imins,&jmins,&ds);     /* 計算雙向預(yù)測的距離*/    /* 場 */    dmcfieldi = bdist1(oldref + (self?width:0) + (iminf>>1) + w2*(jminf>>1),                       newref + (selr?width:0) + (iminr>>1) + w2*(jminr>>1),                       mb,w2,iminf&1,jminf&1,iminr&1,jminr&1,16);    /* 16x8 上半塊*/    dmc8i = bdist1(oldref + (sel8uf?width:0) + (imin8uf>>1) + w2*(jmin8uf>>1),                   newref + (sel8ur?width:0) + (imin8ur>>1) + w2*(jmin8ur>>1),                   mb,w2,imin8uf&1,jmin8uf&1,imin8ur&1,jmin8ur&1,8);    /* 16x8 下半塊 */    dmc8i+= bdist1(oldref + (sel8lf?width:0) + (imin8lf>>1) + w2*(jmin8lf>>1),                   newref + (sel8lr?width:0) + (imin8lr>>1) + w2*(jmin8lr>>1),                   mb+8*w2,w2,imin8lf&1,jmin8lf&1,imin8lr&1,jmin8lr&1,8);   /*選擇距離最小的預(yù)測類型*/    if (dmcfieldi<dmc8i && dmcfieldi<dmcfieldf && dmcfieldi<dmc8f        && dmcfieldi<dmcfieldr && dmcfieldi<dmc8r)    {      /* 內(nèi)插*/      mbi->mb_type = MB_FORWARD|MB_BACKWARD;      mbi->motion_type = MC_FIELD;      vmc = bdist2(oldref + (self?width:0) + (iminf>>1) + w2*(jminf>>1),                   newref + (selr?width:0) + (iminr>>1) + w2*(jminr>>1),                   mb,w2,iminf&1,jminf&1,iminr&1,jminr&1,16);    }    else if (dmc8i<dmcfieldf && dmc8i<dmc8f             && dmc8i<dmcfieldr && dmc8i<dmc8r)    {      /* 16x8, 內(nèi)插*/      mbi->mb_type = MB_FORWARD|MB_BACKWARD;      mbi->motion_type = MC_16X8;      /* 上半塊 */      vmc = bdist2(oldref + (sel8uf?width:0) + (imin8uf>>1) + w2*(jmin8uf>>1),                   newref + (sel8ur?width:0) + (imin8ur>>1) + w2*(jmin8ur>>1),                   mb,w2,imin8uf&1,jmin8uf&1,imin8ur&1,jmin8ur&1,8);      /* 下半塊 */      vmc+= bdist2(oldref + (sel8lf?width:0) + (imin8lf>>1) + w2*(jmin8lf>>1),                   newref + (sel8lr?width:0) + (imin8lr>>1) + w2*(jmin8lr>>1),                   mb+8*w2,w2,imin8lf&1,jmin8lf&1,imin8lr&1,jmin8lr&1,8);    }    else if (dmcfieldf<dmc8f && dmcfieldf<dmcfieldr && dmcfieldf<dmc8r)    {            mbi->mb_type = MB_FORWARD;      mbi->motion_type = MC_FIELD;      vmc = dist2(oldref + (self?width:0) + (iminf>>1) + w2*(jminf>>1),                  mb,w2,iminf&1,jminf&1,16);    }    else if (dmc8f<dmcfieldr && dmc8f<dmc8r)    {       /* 16x8, 前向*/      mbi->mb_type = MB_FORWARD;      mbi->motion_type = MC_16X8;            vmc = dist2(oldref + (sel8uf?width:0) + (imin8uf>>1) + w2*(jmin8uf>>1),                  mb,w2,imin8uf&1,jmin8uf&1,8);           vmc+= dist2(oldref + (sel8lf?width:0) + (imin8lf>>1) + w2*(jmin8lf>>1),                  mb+8*w2,w2,imin8lf&1,jmin8lf&1,8);    }    else if (dmcfieldr<dmc8r)    {            mbi->mb_type = MB_BACKWARD;      mbi->motion_type = MC_FIELD;      vmc = dist2(newref + (selr?width:0) + (iminr>>1) + w2*(jminr>>1),                  mb,w2,iminr&1,jminr&1,16);    }    else    {            mbi->mb_type = MB_BACKWARD;      mbi->motion_type = MC_16X8;           vmc = dist2(newref + (sel8ur?width:0) + (imin8ur>>1) + w2*(jmin8ur>>1),                  mb,w2,imin8ur&1,jmin8ur&1,8);      vmc+= dist2(newref + (sel8lr?width:0) + (imin8lr>>1) + w2*(jmin8lr>>1),                  mb+8*w2,w2,imin8lr&1,jmin8lr&1,8);    }       if (vmc>var && vmc>=9*256)      mbi->mb_type = MB_INTRA;    else    {      var = vmc;      if (mbi->motion_type==MC_FIELD)      {        /* 前向 */        mbi->MV[0][0][0] = iminf - (i<<1);        mbi->MV[0][0][1] = jminf - (j<<1);        mbi->mv_field_sel[0][0] = self;        /* 后向 */        mbi->MV[0][1][0] = iminr - (i<<1);        mbi->MV[0][1][1] = jminr - (j<<1);        mbi->mv_field_sel[0][1] = selr;      }      else /* MC_16X8 */      {        /* 前向 */        mbi->MV[0][0][0] = imin8uf - (i<<1);        mbi->MV[0][0][1] = jmin8uf - (j<<1);        mbi->mv_field_sel[0][0] = sel8uf;        mbi->MV[1][0][0] = imin8lf - (i<<1);        mbi->MV[1][0][1] = jmin8lf - ((j+8)<<1);        mbi->mv_field_sel[1][0] = sel8lf;        /* 后向 */        mbi->MV[0][1][0] = imin8ur - (i<<1);        mbi->MV[0][1][1] = jmin8ur - (j<<1);        mbi->mv_field_sel[0][1] = sel8ur;        mbi->MV[1][1][0] = imin8lr - (i<<1);        mbi->MV[1][1][1] = jmin8lr - ((j+8)<<1);        mbi->mv_field_sel[1][1] = sel8lr;      }    }  }  mbi->var = var;}/* * 幀圖像運動估計 *  */static void frame_estimate(org,ref,mb,i,j,sx,sy,  iminp,jminp,imintp,jmintp,iminbp,jminbp,dframep,dfieldp,tselp,bselp,  imins,jmins)unsigned char *org,*ref,*mb;int i,j,sx,sy;int *iminp,*jminp;int *imintp,*jmintp,*iminbp,*jminbp;int *dframep,*dfieldp;int *tselp,*bselp;int imins[2][2],jmins[2][2];{  int dt,db,dmint,dminb;  int imint,iminb,jmint,jminb;  /* frame prediction */  *dframep = fullsearch(org,ref,mb,width,i,j,sx,sy,16,width,height,                        iminp,jminp);  /* predict top field from top field */  dt = fullsearch(org,ref,mb,width<<1,i,j>>1,sx,sy>>1,8,width,height>>1,                  &imint,&jmint);  /* predict top field from bottom field */  db = fullsearch(org+width,ref+width,mb,width<<1,i,j>>1,sx,sy>>1,8,width,height>>1,                  &iminb,&jminb);  imins[0][0] = imint;  jmins[0][0] = jmint;  imins[1][0] = iminb;  jmins[1][0] = jminb;  /* select prediction for top field */  if (dt<=db)  {    dmint=dt; *imintp=imint; *jmintp=jmint; *tselp=0;  }  else  {    dmint=db; *imintp=iminb; *jmintp=jminb; *tselp=1;  }  /* predict bottom field from top field */  dt = fullsearch(org,ref,mb+width,width<<1,i,j>>1,sx,sy>>1,8,width,height>>1,                  &imint,&jmint);  /* predict bottom field from bottom field */  db = fullsearch(org+width,ref+width,mb+width,width<<1,i,j>>1,sx,sy>>1,8,width,height>>1,                  &iminb,&jminb);  imins[0][1] = imint;  jmins[0][1] = jmint;  imins[1][1] = iminb;  jmins[1][1] = jminb;  /* select prediction for bottom field */  if (db<=dt)  {    dminb=db; *iminbp=iminb; *jminbp=jminb; *bselp=1;  }  else  {    dminb=dt; *iminbp=imint; *jminbp=jmint; *bselp=0;  }  *dfieldp=dmint+dminb;}/* * 場圖片運動預(yù)測程序 * * toporg：原始上半部分場地址
 *topref：重建的上半部分場地址
 *botorg：原始下半部分參考場地址
 *botref：重建的下半部分參考場的地址
 *mb：待匹配的宏塊
 *i，j：宏塊的位置（即搜索窗口的中心）
 *iminp，jminp，selp，dfieldp：最佳預(yù)測場的位置和距離
 *imin8up，jmin8up，sel8up：上半部分宏塊的最佳預(yù)測的位置
 *imin8lp，jmin8lp，sel8lp：下半部分宏塊的最佳預(yù)測的位置
 *d8p：最佳16×8的預(yù)測塊的距離
 *iminsp，jminsp，dsp：最佳同奇偶性預(yù)測場的位置和距離
 */
static void field_estimate(toporg,topref,botorg,botref,mb,i,j,sx,sy,ipflag,  iminp,jminp,imin8up,jmin8up,imin8lp,jmin8lp,dfieldp,d8p,selp,sel8up,sel8lp,  iminsp,jminsp,dsp)unsigned char *toporg, *topref, *botorg, *botref, *mb;int i,j,sx,sy;int ipflag;int *iminp, *jminp;int *imin8up, *jmin8up, *imin8lp, *jmin8lp;int *dfieldp,*d8p;int *selp, *sel8up, *sel8lp;int *iminsp, *jminsp, *dsp;{  int dt, db, imint, jmint, iminb, jminb, notop, nobot;  /* 如果ipflag為1則僅從對偶場預(yù)測 */  notop = ipflag && (pict_struct==TOP_FIELD);  nobot = ipflag && (pict_struct==BOTTOM_FIELD);   /*場預(yù)測*/
  /* 從上半部分場預(yù)測當(dāng)前場 */  if (notop)    dt = 65536;   else    dt = fullsearch(toporg,topref,mb,width<<1,                    i,j,sx,sy>>1,16,width,height>>1,                    &imint,&jmint);   /* 從下半部分場預(yù)測當(dāng)前場*/  if (nobot)    db = 65536;   else    db = fullsearch(botorg,botref,mb,width<<1,                    i,j,sx,sy>>1,16,width,height>>1,                    &iminb,&jminb);  if (pict_struct==TOP_FIELD)  {    *iminsp = imint; *jminsp = jmint; *dsp = dt;  }  else  {