My general feeling is that such video processing on a shared server is too resource intensive, but that is not to say that, if lightly enough used, you might not can make it work (though you'd likely be in a constant hide and seek game with procwatch!)
That said, ffmpeg is installed already, but you may need to reinstall your own to have it properly configured for most of the "YouTube" clone stuff I have seen.
The other stuff you listed is not installed, and you will have to do that yourself. Some have succeeded with this, but many can't seem to do it. You will also most certainly need your own custom PHP install, for a myriad of resource related reasons.
One note, you will need to install autoconf before installing ffmpeg-php - that seems to throw quite a few people trying to do this.