Alternative to Slideshare

Looking for build in an open source version similar to Slideshare. Certainly you know that the new Google Hangout/s/ uses the technology of Slideshare. . Please give me your estimate to the following task regarding my own app. in developing status. As "demo" pls. watch on this side the first video [login to view URL] As you could see: -at 1:20 from the start, -the man from the webcam into the bigger player /David Poulin/ says: -"...lookin the slides..." than - from 1:47 the slides appear on the big player "before" David one by one /they fill the big player/ and we hear David's voice. Then, at the end of presentation of the documents on the screen, David appears again. So I like to have a very similar solution for our Moderator, who will sit on a similar big player. Each Moderator /Client/ has an own webadmin and surely /??/ he should be able -to upload his files on our Wowza server, prior of the live show -and when he choose to show this files to the audience -to be able to show one by one /play/stop/ his slides and -these slides should fill the whole big player Next to your estimate please tell me how many days could you code it into the Wowza server side script. If you need help in Wowza server side programming, I could contact you with a developer.