I'm thinking of getting an ATV for my parents who want to be able to view their pics on the TV and play music through it. What sources of photos/music does the apple TV support. My parents photo and music library sit on a macbook. They have some pics in the photo stream but would also like to have some albums they can use for screensaver that currently reside on their MB. Do they need to have their macbook on for them to stream these or can they be transferred to the cloud (any limitations on number?) or the ATV itself?