ref:http://www.real.com/linux
I found the newest version Realplayer for linux:RealPlayer 11 for Linux.
and I have extracted the codec files.
There are the newest rmvb decoder in it,maybe it can improve the
capability of playing rmvb.
But I don't know how to use it .

You can download the codecs from here:
http://www.myhtpc.com.cn/attachment.php?aid=2553
if anyone knows how to use it,please tell me.
Thank you.

As I mentioned obliquely in the other thread (why start another one?), these are x86 binaries, they are not usable on the ARM processor we have. Look at what Helix libraries are provided and see if mplayer links against them.