[MPlayer-dev-eng] How does the OSD(on screen display) layer of MPlayer work?

[JW]

Recently, I hava some trouble with reading the sourcecode of MPlayer.
I want to add personal information to the OSD layer,just like the subtitles,so I shoud have known how the subtitles show up on the OSD layer. 


I have found that most relative functions are in the file ./sub/sub.c. But there are too many functions that I can't understand it.


Does anyone know something about it. Thanks :)