iTunes has to be running, however, if the computer is asleep, it will wake to serve the network request if your settings are correct.I have a MacBook Pro as well as an iPhone 4. So do I have to have my MacBook up and running in order to access my movies through Home Sharing if I already dumped them into iTunes?
An important note is that iTunes must be running to use home sharing. We have all our iTunes content on a server that runs 24/7 so it's always available to the ATV (and iPad/iPod/iPhone/other computers).
We have several hundred movies in our iTunes libraries and the kids watch them frequently (both on the ATV and via other devices in the house).
Airplay Mirroring will share whatever is on you MacBook screen. So if your browsing the internet, you could do that on your TV using Airplay Mirroring. Airplay Mirroring content is pushed to the ATV and requires that you use the MacBook to control what's on the TV.One more question. Is more advantageous to use Home Sharing over AirPlay Mirroring my MacBook Pro?
Airplay Mirroring will share whatever is on you MacBook screen. So if your browsing the internet, you could do that on your TV using Airplay Mirroring. Airplay Mirroring content is pushed to the ATV and requires that you use the MacBook to control what's on the TV.
Home Sharing only works for content in iTunes and that content is pulled by the ATV. You only need the ATV remote for this.
But in terms of playing movies, is one a better option than another?
Don't forget that with home sharing, the ATV is pulling down as much of the movie it can, as fast as it can. Airplay is "live". This means that Home Sharing isn't as sensitive to interference or spotty network, and the computer can even go to sleep after the movie is downloaded instead of having to be turned on during the whole thing.Home sharing is the better choice then because with Airplay you get some quality loss.
I use a mid 2010 mac mini server to handle the iTunes content for the house in addition to handling the other server tasks it does (mainly it's used as an account server so that all the kids accounts are available at any mac they want to use).
Pretty much any computer on your network that will run iTunes can act as an iTunes server. You don't need any special software for that. Simply load all your content into iTunes on that computer, enable home sharing, and you're all set.