Change bidir refine hash code so we only need to perform a single

hash calculation for the whole function.
negligibly faster (about 0.1%)

Originally committed as revision 22775 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/motion_est.c

@@ -1475,12 +1475,12 @@ static inline int bidir_refine(MpegEncContext * s, int mb_x, int mb_y)
     const int ymin= c->ymin<<shift;
     const int xmax= c->xmax<<shift;
     const int ymax= c->ymax<<shift;
+#define HASH(fx,fy,bx,by) ((fx)+17*(fy)+63*(bx)+117*(by))
+    int hashidx= HASH(motion_fx,motion_fy, motion_bx, motion_by);
     uint8_t map[256];
 
     memset(map,0,sizeof(map));
-#define BIDIR_MAP(fx,fy,bx,by) \
-    map[((motion_fx+fx)+17*(motion_fy+fy)+63*(motion_bx+bx)+117*(motion_by+by))&255]
-    BIDIR_MAP(0,0,0,0) = 1;
+    map[hashidx&255] = 1;
 
     fbmin= check_bidir_mv(s, motion_fx, motion_fy,
                           motion_bx, motion_by,
@@ -1491,12 +1491,13 @@ static inline int bidir_refine(MpegEncContext * s, int mb_x, int mb_y)
     if(s->avctx->bidir_refine){
         int score, end;
 #define CHECK_BIDIR(fx,fy,bx,by)\
-    if( !BIDIR_MAP(fx,fy,bx,by)\
+    if( !map[(hashidx+HASH(fx,fy,bx,by))&255]\
        &&(fx<=0 || motion_fx+fx<=xmax) && (fy<=0 || motion_fy+fy<=ymax) && (bx<=0 || motion_bx+bx<=xmax) && (by<=0 || motion_by+by<=ymax)\
        &&(fx>=0 || motion_fx+fx>=xmin) && (fy>=0 || motion_fy+fy>=ymin) && (bx>=0 || motion_bx+bx>=xmin) && (by>=0 || motion_by+by>=ymin)){\
-        BIDIR_MAP(fx,fy,bx,by) = 1;\
+        map[(hashidx+HASH(fx,fy,bx,by))&255] = 1;\
         score= check_bidir_mv(s, motion_fx+fx, motion_fy+fy, motion_bx+bx, motion_by+by, pred_fx, pred_fy, pred_bx, pred_by, 0, 16);\
         if(score < fbmin){\
+            hashidx += HASH(fx,fy,bx,by);\
             fbmin= score;\
             motion_fx+=fx;\
             motion_fy+=fy;\