It depends on what you want to do with it: private, free internet streaming or commercial.
Please read <http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Patent_licensing> and follow the links leading to related articles.
It's a complicated set of licensing. The most important thing though is: "On August 26, 2010 MPEG LA announced that H.264 encoded internet video that is free to end users will never be charged royalties".
You might also take a look at: http://www.streamingmedia.com/Articles/ ... leID=65403