@@ -901,6 +901,8 @@ static int interlaced_search(MpegEncContext *s, int ref_index,

             int16_t (*mv_table)[2]= mv_tables[block][field_select];

             if(user_field_select){

+                assert(field_select==0 || field_select==1);

+                assert(field_select_tables[block][xy]==0 || field_select_tables[block][xy]==1);

                 if(field_select_tables[block][xy] != field_select)

                     continue;

             }