Under The Microscope

A Tour of Airfoil 3

We’ve just released Airfoil 3 and it has a lot of great new features we’ve been hard at work on for over a year. So join us on a tour of all the stuff that’s been added in Airfoil 3.

Airfoil Speakers

The first thing you’ll notice when opening the download is this little app called Airfoil Speakers:


Airfoil Speakers

Airfoil Speakers works as a virtual AirPort Express. You can run this little application on any computer you have connected to your local network. Once you do, that computer will show up as a remote speaker in Airfoil 3 and you can send audio to it.

Airfoil Speakers

Now your extra Macs can share the fun alongside your AirPort Expresses to get your audio into even more places. Airfoil Speakers can show the nice window seen above with spec meters and a volume control, or you can just tuck it away as an icon in your menu bar for minimal intrusion.

Airfoil Speakers works pretty much like an AirPort Express from the point of view of Airfoil. It advertises its services over Bonjour, then uses the same AirTunes 2 protocol that Apple uses. However, despite using the same protocol, iTunes won’t talk to Airfoil Speakers. iTunes uses cryptographic authentication to ensure that it only talks to real AirPort Expresses, and we weren’t able to mimic that. Until Apple removes those checks, Airfoil Speakers will only work with Airfoil 3 and Airfoil for Windows.

Local Playback

This feature is pretty obvious when you open Airfoil 3 and see the first entry in the main window:

Computer Output

That “Computer” speaker is always there, and represents your local computer. Airfoil 2 could do local playback, but it didn’t delay the audio at all. Thus, everything played locally several seconds before it was heard remotely, making for a jarring experience. Now in Airfoil 3, the “Computer” speaker is delayed by exactly the same amount as the remote speakers, allowing your main computer to become a seamless part of your audio system.

Airfoil Video Playback

Another great new addition in Airfoil 3 is the shiny new Airfoil Video Player:

Airfoil Video Player

You can find Airfoil Video Player right in the source popup in Airfoil, or you can just drag a movie file right onto Airfoil and it will start Airfoil Video Player for you. AVP uses QuickTime and Perian to play all sorts of media files, and all with perfect synchronization between audio and video. AVP can’t play everything – it needs to control the files, so they need to be local, not web-based. Likewise, Apple’s FairPlay DRM prevents playback, which means AVP can’t play movies purchased from iTunes. But thanks to QuickTime and Perian, we support dozens of popular video formats. Now you can watch your favorite movie files through your nice stereo system without needing any wires from your computer. And although support is still preliminary, Airfoil Video Player can play DVDs, also perfectly synchronized.

If you pop open Activity Monitor, you might notice that Airfoil Video Player takes up a bit more RAM and CPU than your usual video player. You might also notice that when you press Play, the movie doesn’t actually start to move for about two seconds. Both of these are due to how Airfoil Video Player works inside.

The AirTunes 2 protocol has some delay built in to it, and when sending to remote speakers with Airfoil 3 the audio is delayed by two seconds. AVP has QuickTime play the movie as usual, but doesn’t display it to the screen. While the audio heads out to Airfoil and your remote speakers, the video gets buffered internally to AVP. Once two seconds’ worth of video has been buffered, AVP starts to draw them to the screen, resulting in perfect synchronization between video and audio output. This is a bit more resource intensive since AVP has to keep two seconds of video frames in memory at all times, but it turns out that on modern machines this doesn’t have much of an impact. Even playing back a smooth 1080p video trailer downloaded from Apple’s movie trailers uses under 200MB of RAM for the buffer, and other types of video generally use much less.

Perfect Sync

Airfoil 2 introduced the ability to send to multiple remote speakers simultaneously, and it did a pretty good job of keeping playback synchronized while doing it, but there were limitations on just how good it could be. Thanks to a new network audio protocol (AirTunes 2), Airfoil 3 is able to keep all remote speakers playing in perfect sync with each other.

This new protocol is also what allowed us to add all of the other new features discussed above and keep local audio and video playback in perfect sync with remote audio coming both from the AirPort express and from Airfoil Speakers.

Get It While It’s Hot

So there you have it, the four big new features in Airfoil 3. I hope you enjoyed this tour and I hope you enjoy the app! You can learn more on the Airfoil site or just download directly.


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