Mencoder srt or ass style formating gone

Anyone know how to retain the original style for ass or srt.

For srt , i wanna put a line or two at top poisiton i will use like

1
0:00:10.00 --> 0:00:20.00
{\a6}Hello world top

and it will display at the top center of the screen but mencoder ignore {\a6} and take it as a text

Then for ass i will use

Style: Baoky,Comic Sans MS,32,&H001FEBEE,&H0000D6FD,&H00000000,&H00000000,-1,0,0,0,100,100,0,0,1,2,2,8,10,10,10,1

Dialogue: 0,0:05:00.00,0:05:15.00,Baoky,,0000,0000,0000,,Hel lo world top


it also ignore the position style. How do i let mencoder retain the format when i add the subtitle into video, else can i use 2 subtitle tracks in 1 convert means -sub normaltext.ass -sub toptext.ass -subpos 1

is it possible or not possible thanks