Best thing here is to install some temp & fan monitoring software to monitor what your system is doing. I like '''Temperature Gauge''' which you can find on the Apple App Store. Then you can see if something is not working correctly as well as see what you are doing causes it to heat up the most.
As to what you are doing Vids using Flash tend to push the system hard which will cause it to get warm (the longer the vid the warmer it will get). You may want to try using QuickTime or other video standard (if you are making your own here).
You may also have something else running on your system that is sapping it of CPU cycles which in turn cause it to overheat. Adware & Malware which you didn't ask for. Get a good anti-virus app with the latest definition file they have. Heres a good write up on what you can encounter '''[http://arstechnica.com/information-technology/2013/08/download-me-ii-removing-the-remnants-of-the-webs-most-dangerous-search-terms/|Who knew that "free" could lead to a PUP? (Sadly, not the cute and cuddly kind.)]''' You can also run Apples '''Activity Monitor''' which you'll find in your Applications Utility folder.
Let us know what you find.