This could be a bug.
I am using 4.14.1, and I cannot use video textures AT ALL.
I tried finding tutorials and instructions and finally noticed that when I bring up the FileMediaSource editor, there is NO “details” section at all. It is blank.
There SHOULD be a details section like in this video but there is not. It is just blank. Not even the “details” title is displayed… take a look at the screenshot I attached.
This looks like you just accidently closed the details panel from this window. In this window tab go to the menu and select Window and make sure that Details is checked.
