滚动的字幕是怎么做的？

[Script Info]; This is a Sub Station Alpha v4 script.
; For Sub Station Alpha info and downloads,
; go to http://www.eswat.demon.co.uk/
; or email kotus@eswat.demon.co.uk
ScriptType: v4.00
Collisions: Normal
PlayResY: 288

[V4 Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, TertiaryColour, BackColour, Bold, Italic, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, AlphaLevel, Encoding
Style: MainT,Arial,14,65535,65280,65535,0,0,0,1,2,4,5,16,16,16,0,0
Dialogue: Marked=0,0:00:01.00,0:00:25.00,MainT,,0000,0000,0000,Banner;30,AAAAAAAAAAAAAAAAAAAAAA.
Dialogue: Marked=0,0:00:01.00,0:00:25.00,MainT,,0000,0000,0000,Scroll Up;20;250;10,{\q1}AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA




这个怎么用啊