Video/FMS Question - Compositing video with border?

I have a question for people who deal with video and FMS.

Is it possible to add a border to a video? Say you have a transparent .png and render into the video…

Could it be done serverside?

My current solution is just to save a border selection variable to the database which is then sent to flash lite which selects the correct border to place over the video. (This is for mobile content.)