using mediaElement object to show clip

I want to use MediaElement to show some small clip. But some of the clips format that i have are mp4, AVI ...

I try 开发者_运维问答to load them to the MediaElement and 'play' tham but i can see anything. Is it possible to see them somehow on the MediaElement ?

There is no AVI support in Silverlight (it missed on overview of Silverlight).
One way is to convert them to WMV with Microsoft Expression Encoder.
For MP4 files there is question on SO : How to play MP4 (H.264 video) in Silverlight 3 (or 4) from a URL?.

Hope this will help.