[whatwg] HTML 5 video tag questions

[jjcogliati-whatwg at yahoo.com]

I read section 4.8.7 The video element and I have some questions:
1.  What happens if the user agent supports the video tag but does not support the particular video codec that the video file has?  Should it display the fallback content in that case, and if so, can a video tag be put inside another video tag?
2.  What is the recommended way for website authors to determine what video and audio codecs and containers are supported by a user agent? 

Joshua Cogliati
http://jjc.freeshell.org/