Apple released OS X Mountain Lion preview today ahead of the planned summer release and we briefly touched upon some of the more important features like the all-new Messages app, Gatekeeper anti-malware capabilities, enhanced local services for the Chinese, system-wide Twitter integration and brand new iOS-like Notification Center. Tucked away as a side-note in Apple’s press release is AirPlay Mirroring, another welcome addition to Mountain Lion’s arsenal of over a hundred new features (so claims Apple).

Yes, there are a few apps for that, though, I have yet to find one that works as seamlessly and effortlessly as AirPlay implementation on iOS devices. Eagle-eyed readers could point out that AirPlay support was long-planned for Lion until it was abruptly pulled last-minute without an explanation. Sure enough, it took longer than expected, so we are excited with full AirPlay Mirroring now a possibility on Macs running Mountain Lion.

Just as you would expect, AirPlay Mirroring in Mountain Lion lets you tunnel whatever is on your Mac wirelessly to your television through the Apple TV set-top box. Think web pages in Safari, kitten clips on YouTube, movies from iMovies, Keynote presentations or any other content displayed on your Mac, including your desktop. Yes, just like on the iPad.

Better yet, using AirPlay Mirroring on 2011 Mac notebooks does not need a local wireless network, because the machine can create an ad hoc wireless network to pair with the Apple TV. This is gold for road warriors and educators who only need a MacBook and an Apple TV to present their portfolio or teaching material on the big screen.

There are some caveats, though.

First, Apple advised matching TV resolution to your Apple TV to achieve a sharper image. Secondly, the press release mentioned that AirPlay Mirroring sends a 720p video stream to your Apple TV— meaning large desktops are downscaled to a 1280-by-720-pixel resolution. This is likely a hardware limitation of the current-generation Apple TV that lacks 1080p video output. However, this downscaling business will tax your Mac hardware, especially at 30 frames per second, so you will need a decent graphics card and preferably one of the Intel Core CPUs that can handle AirPlay video compression in real-time.

Factor in a slight but annoying lag stemming from wireless networking and real-time video compression/decompression and you are unlikely to use AirPlay Mirroring to beam fast-paced action games from your Mac to your television. Now, Apple introduced new streaming APIs in the Core Graphics framework to help AirPlay Mirroring, and they make it easier to capture updates to the display in a real-time. These new APIs also provide for scaling and color space conversion services and they support viewing and modifying metadata for popular image formats.

AirPlay Mirroring is already present in the developer preview of Mountain Lion and it works as advertised – discovering your Apple TV automatically with no setup required. It was not immediately clear if AirPlay Mirroring works out-of-the-box with any existing app on the Mac. The wording of Apple’s marketing collateral indicates app developers will need to add support for AirPlay Mirroring—meaning some Mac apps may specifically prohibit content streaming through the Apple TV. Regardless, it is the last piece of the puzzle as AirPlay Mirroring is now available across the Mac, iPhone 4S, and iPad 2.

Conceivably, AirPlay Mirroring on the Mac helps make the most from your $99 set-top box, because you can keep a bunch of movies on your Mac and stream them to your television without importing files to iTunes first. Up next: AirPlay Mirroring in 1080p will need a third-generation Apple TV with 1080p video output, and (we’re afraid) new Apple gear sporting Gigabit Wi-Fi technology (the chips are already here), because the current 802.11n wireless standard lacks sustainable bandwidth needed for full HD video streaming.

  • Apple announces Mac OS X 10.8 Mountain Lion Developer Preview with deeper iOS integration (9to5mac.com)
  • Tim cook talks Mountain Lion (9to5mac.com)
  • Apple posts Messages Beta for the Mac on the heels of Mountain Lion announcement (9to5mac.com)
  • Here, Apple’s demo video for Mountain Lion (9to5mac.com)
  • Mountain Lion available for download (9to5mac.com)
  • Apple hooks up exploding Mac user base in China with local services in OS X Mountain Lion (9to5mac.com)
  • Mountain Lion isn’t a walled garden (yet), but it has a Gatekeeper (9to5mac.com)