prepped for a series of lectures in Brazil by learning Spanish (with ensuing audience laughter), the physicist's comment is "Portuguese is the national language of Brazil." Unlike typical director's/actor's commentaries on movie DVDs, the comments are in text only, so you can actually watch the videos effectively with the commentary, rather than watch the videos first, then (maybe) watch them again with commentary (if you don't want to be able to hear the movie). It's a great example of Project Tuva's creators' efforts to focus on what really works, rather than go to multimedia excess.
To the left of the video, there's a note-taking function that allows the user to write notes as the video is playing - these notes get tagged to the video at the precise point in the video you made them, and get automatically added to a video timeline as well (more on this below). If you want to save your notes for the next time you watch the video, you can click an "Export" button, which allows you to save out your notes as a text file with time hooks into the video preserved. At that point, you can share your notes with others (e.g. your students) and you or they can load them whenever they watch the video as well. What's more, you/they can load them as the running commentary on the video (instead of using the default experts or peers for this), to add a more user-