web base playout

hello to all
i am starting this new topic to discuss about the programming tools and libraries for creating a web playout. i mean not desktop application and just web page to log in to it and start playing the playlist.
i searched in google and i know that companies like cynergy,veset,playbox, imagine etc. are working on cloud playout which is great. also h-tech is proposing a web playout .
my question is, how they decode the video,add CG, and stream the video out?
is it possible to use Direct Show o Media foundation on web application?
is there any other tool for doing all playout and CG tasks on web?
what about Silverlight? can we use it for developing professional web base playout?

suppose that i am going to start a web playout project today. what are the requirements and which programming language do you suggest?

i will be glad to hear your valuable comments
nothing is impossible