As far as I know Google do not want outside parties to play their videos except via the official YouTube site and embedding APIs; indeed doing so is likely to be a violation of their TOS. That does not mean you cannot get at the direct underlying MP4 streams, just that Google do not make it easy for the links to them to be found, However, if you are prepared to put a bit of effort in analyzing web requests and their returned HTML you can eventually piece together enough information to figure out how to translate a video id into a series of MP4 streams (of different qualities). I'll warn you now, it isn't trivial.
I doubt any channel based on such a circumvention would pass as a public channel, but that doesn't mean you can't code something just as a personal challenge, for your own amusement. 😉 Suffice to say you're not the first programmer in the World to ask such a question, so your first port of call should probably be Google...
