Anonymous - 2012-05-06

I am new to using any media servers.  So far I like MediaTomb.  I encode all my movies the same way.  I use Handbreak and  encode using the .m4v format.
I would say 99% of my movies show up and play on all devices, but there are a few movies that do not.  Why is that? How do I make all movies show up in the list and play on all devices (Android tablets, Ipads, AppleTV, and PC and Mac computers.
Thanks for any help or advice.