If you’ve got an Apple AirPort Express, you can use iTunes to “broadcast” your music, wirelessly, to speakers connected to the Express. (Apple calls this technology “AirTunes.”) Unfortunately, AirTunes has several drawbacks, the most significant of which is that it can broadcast only audio playing in iTunes. If you want to listen to audio that isn’t supported by iTunes—for example, Real Audio, Windows Media files, or audio being played in a Web browser—you’re out of luck.
Last year I reviewed Rogue Amoeba’s $40 Nicecast ( ), a utility that allows you to stream audio from within any application over the Internet. As it turns out, you can use Nicecast to stream audio from other applications into iTunes, which can then send that audio to an AirPort Express. Presto—AirTunes for any application. Macworld even awarded Nicecast a 2004 Eddy Award for this capability. But the truth is that this is really just a clever kludge, and it’s a bit of a hassle to get working: First you have to set up the audio stream, then you have to configure iTunes to “receive” it, then you have to broadcast to your AirPort Express.
This isn’t intended to be criticism of Nicecast—the application wasn’t originally designed to perform such iTunes trickery. Nevertheless, the folks at Rogue Amoeba realized that they had discovered something quite useful, so they set out to make it easier to use. The result is the new $25 ($20 introductory price through the end of March) Airfoil ( ). Put simply, Airfoil lets you stream audio from any single application directly to a chosen AirPort Express. And it couldn’t be easier to use.
In Airfoil’s main window, you first choose the running application—from the Select pop-up menu—that’s providing the audio you wish to transmit. (The menu also lists recent applications used in Airfoil, as well as a Select Application item that lets you choose an application that isn’t currently running. If you option+click the menu, hidden applications are also shown.) You then select the AirPort Express unit to which you wish to transmit. (If you’ve only got one, it will be selected by default.) Finally, you click the Transmit button. The application’s audio will begin playing through your AirPort Express (or should I say through any speakers connected to that AirPort Express). You can control the volume level of the signal via Airfoil or, if you prefer, you can set Airfoil’s preferences so that it links its own volume level to your Mac’s volume control.
Using Airfoil, you can easily broadcast audio from Windows Media Player, Real Player, MPlayer, QuickTime Player, or any other application that produces audio, including games and Web browsers. The latter makes it a great way to listen to Web broadcasts of sporting events on your home stereo. However, keep in mind that just like iTunes, there’s a slight delay between when a sound is produced by an application and when it’s played back by your AirPort Express, so don’t expect to watch a DVD on your computer while playing the audio back through your stereo. (Actually, this is possible, though not without glitches: The free MPlayer OS X and VLC media player have audio offset/de-sync features that let you manually sync the audio and video of a DVD; the Airfoil Help system provides details on setting this up.)
Airfoil even offers advantages for those who are simply broadcasting iTunes audio. For example, whereas AirTunes mutes local audio when broadcasting, you can set Airfoil’s preferences to play audio on the local computer while it’s being played via your AirPort Express. (Note that because of the way AirPort Express audio transmission works, local and remote audio may be slightly out of sync.) And whereas audio effect plugins (such as the popular Volume Logic ) don’t work with AirTunes, they do work via Airfoil. You simply need to set iTunes to play locally on your computer—not via AirTunes to your AirPort Express—and let Airfoil send the audio.
One quirk with Airfoil has to do with how it interacts with running applications. (I reluctantly call it a “quirk,” as it’s really a conscious decision by the developers, intended to address the concerns of users.) If you elect to install Airfoil’s “Instant Hijack” component—you’re given the option the first time you launch the application, or you can install it at any time by choosing Airfoil -> Install Extras—then clicking the Transmit button commences the transmission immediately. However, Instant Hijack uses Unsanity’s Application Enhancer technology. Some people refuse to use software that requires Application Enhancer, citing stability issues, so Rogue Amoeba has wisely devised a way for Airfoil to work without it. The drawback is that in order for this workaround to function, you need to either select the desired audio application in Airfoil before it’s launched, or allow Airfoil to relaunch it if it’s already running when you begin transmission. It’s up to the user to decide which method—Application Enhancer or inconvenience—to choose.
Airfoil also offers a few hidden settings for advanced users, accessible by option+clicking the Transmit button. You can adjust the stream index; decide what happens when no audio is detected (stop the stream, add silence, or add noise); and customize audio device and channel settings. You can also choose the measurement displayed by Airfoil’s audio meter by clicking on the meter and choosing the desired option (Off, In RMS, In Peak, Out RMS, or Out Peak) from the resulting pop-up menu.