A colleague did the work on Presto for example. http://www.singularsoftware.com/presto.html
I've never used it but I know the author and looks like something that may be close to what you are looking for.
Remember this is very high end. That is, you won't get this cheap today.
I'm using Adobe Premiere 8 for video editing, and I was wondering with use of a Chromakey Green Screen what software would be best suited to construct or design a virtual studio?