Problem among BSPlayer(812), ffdshow+XviD, and Vobsub2.33

[kernalwave]

I know BSPlayer just support .srt/.ssa/.sub subtitles except using Vobsub.
But recently, i find something interesting.

I have some avi files with their plugin-subtitle files .ass.
Usually i like using ffdshow to replace xivd to process video part, but i still have installing xvid decodc.

When i used BSPlayer to play avi+ass, if using xvid as a video decoder, the subtitle is working; the green arrow will appear on the buttom of right corner of the screen; if using ffdshow as a video decoder, it doesn't work.
But when i use Media Player Classic, eveythin is fine either using ffdshow or xvid. But i still like the the location of control panel under full screen; it's much better than MPC ...

i had tried as many means as i could think with my limit wisdom but i still can get it. ><

Is there anyone can give me a help ??? Thank you everyone very much.