If you are not familiar with Plex then you should take a look at their website.
Plex organizes your video, music, and photo collections and streams them to all of your screens.
What this explanation leaves out is that Plex will handle all of the details for you fairly seamlessly. Whatever format your collection is in, Plex will automatically ensure that it is compatible with whatever device you are using to view the collection. First I will explain how to install it on FreeNAS and then I will talk more about the software itself.