I subscribe to a legal music video download service which provides videos in mp4 format. They play on multiple PCs with various software, phones, tablets, in fact everything except ..... the ipad.
Itunes won't even transfer the files at all.
Their genius says I have to install a 3rd party player then transfer the files within that to get them to play.
Ermmmmm No. £409 refund please.
I guess Apple don't want people playing movies that haven't been bought from their store in their specific codec then.