Split first reference list comparission from mv comparission.

about 0.5% faster MBAFF loop filtering

Originally committed as revision 21552 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264_loopfilter.c

@@ -418,9 +418,10 @@ void ff_h264_filter_mb_fast( H264Context *h, int mb_x, int mb_y, uint8_t *img_y,
 static int check_mv(H264Context *h, long b_idx, long bn_idx, int mvy_limit){
     int v;
 
-    v = h->ref_cache[0][b_idx] != h->ref_cache[0][bn_idx] |
-        h->mv_cache[0][b_idx][0] - h->mv_cache[0][bn_idx][0] + 3 >= 7U |
-        FFABS( h->mv_cache[0][b_idx][1] - h->mv_cache[0][bn_idx][1] ) >= mvy_limit;
+    v= h->ref_cache[0][b_idx] != h->ref_cache[0][bn_idx];
+    if(!v && h->ref_cache[0][b_idx]!=-1)
+        v= h->mv_cache[0][b_idx][0] - h->mv_cache[0][bn_idx][0] + 3 >= 7U |
+           FFABS( h->mv_cache[0][b_idx][1] - h->mv_cache[0][bn_idx][1] ) >= mvy_limit;
 
     if(h->list_count==2){
         if(!v)