Short Answer
This is a bit of a gray area. The short answer is “If the video can be loaded and played in Vernier Video Analysis or Logger Pro, then you can use the analysis tools to analyze the video.”
Long Answer
The long answer is that it can be tricky to move video from one format to another. In some cases, the video is copyright-protected, and made intentionally difficult to transfer into a different format. Note that many video files are copyright-protected and attempting to break that protection may be illegal.
- To download files from YouTube and other web sites, there is a FireFox extension called “Video Download Helper”, which is a free download
https://addons.mozilla.org/en-US/firefox/addon/3006 - To get files from a DVD, there are several options which are often embroiled in legal battles. The most popular one is called HandBrake.
http://handbrake.fr/
Note that it may not rip all DVDs due to encryption.