How to use AirPlay Mirroring in Mountain Lion

Watch this: Bring your Mac desktop to the big screen

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If you've managed to get your hands on Mountain Lion for Mac, there's a really cool feature called AirPlay Mirroring where you can show your desktop and more on a big screen hooked up to an Apple TV. AirPlay Mirroring is something you might use when you want to show your work at a meeting, show your photos to your family, watch video, and so on, but on an Apple TV-connected big screen. Here's how to do it.

Editors' note:Unfortunately, AirPlay Mirroring only works on Macs made in 2011 or later. For those on older machines running Snow Leopard, try AirParrot.

You start by making sure your computer is on the same network as your Apple TV, then look for the monitor-shaped icon in your Menu bar -- Mountain Lion automatically detects when an Apple TV is in range. To start AirPlay Mirroring, select Apple TV from the AirPlay drop-down menu.

The first thing you'll probably notice is there is a little bit of lag between your laptop and the TV, but you can open windows, move files around, or whatever you want, and you can see it all on the big screen.

With your desktop on the big screen, there are several ways you can take advantage of the larger viewing area. If you have photos on your Mac, AirPlay Mirroring is the best way to display them to a roomful of people. Simply launch iPhoto or whatever photo management program you prefer, switch to full screen on your Mac, and flip through full-size images or start a slideshow.

Next, you can try checking out video. Obviously, with Apple TV you already have connections to YouTube and Netflix, so there's not much point in mirroring those services on your big screen. The major advantage of AirPlay Mirroring in Mountain Lion is that you can show Flash movies -- something iPhones and iPads with iOS 5, which also have AirPlay Mirroring, cannot do. To check out a movie, pick your favorite Flash-based media site, such as Hulu, Comedy Central, or a major network TV site. Once you've decided on a TV episode or movie, switch it to full screen and enjoy the show. This feature will be particularly useful for those who don't have a traditional cable service and will open up a whole new library of TV and movies to watch.

AirPlay Mirroring not working properly? Try these fixes.
I've heard about some people encountering problems with audio transferring to a big-screen TV, but it's usually a pretty easy fix.

Obviously you'll want to make sure the audio volume is up on both devices. But if you're still having trouble, go to the Apple menu to open System Preferences, choose Sound, then under the Output tab make sure Apple TV is selected. Close the window, try it again, and you should be able to hear audio coming from your TV's sound system no matter what you're showing.

If it's the picture giving you problems, there are a couple of ways to make it look better. If you're noticing black bars on the top and bottom or on all sides, try going to System Preferences, then choose Displays. Now, click the radio button that says "Best for AirPlay." This should make the picture fit the larger screen size and aspect ratio of your big-screen TV.

If you're noticing that you don't seem to be able to view the full area of the movie or show you're watching, click the AirPlay button in your Menu bar (the monitor-shaped icon), select Displays (you can also get there via the System Preferences), than uncheck Overscan. It's wise to try it both ways to see which way looks better to you.

AirPlay Mirroring is one of the best new features in Mountain Lion, for conducting meetings, showing your photos to a room, and especially for the number of new TV and movie possibilities. Hopefully with these tips you can get your AirPlay Mirroring working so you can enjoy your desktop on the big screen.