Hidden Features
Airfoil has a few features of which you may not be aware. Read this page for details on some of the lesser-known features of Airfoil.

Monitoring Output Locally
With Airfoil, you can play audio remotely, and locally as well. This option is off by default, as local audio will be out of sync with remote playback. If you'd like to turn this option on, select 'Monitor Locally' from the Audio menu in Airfoil.

Transmitting Audio From Previously Open Applications
By default, Airfoil must relaunch applications to grab their source audio. With the Instant Hijack component installed, Airfoil can pull audio from applications which are already open. To learn more, see the "Install Extras..." menu option in the Airfoil menu.

Transmitting Audio From Hidden Applications
Airfoil can transmit audio from some hidden applications, but they don't show up in the ordinary Audio Source popup menu at the bottom of Airfoil's main window. To view these hidden applications, hold down the option key when you click the menu.

Minimize Behavior
By default, Airfoil will minimize to the Dock. By adjusting the Preferences, Airfoil can be made to minimize to the Menu Bar. To reverse the currently-set behavior, hold down option when minimizing.

Advanced Hijacking Options

This sheet allows access to the Advanced Hijacking options. To access it, select Advanced Source Settings... in the Audio menu when an application is set as the audio source. Most of these settings should be left at their defaults, but adjusting the Stream Index may allow you to receive audio from applications from which Airfoil ordinarily does not receive audio.
Hijack Settings
Stream Index: Adjusting the Stream Index may allow you to receive audio from applications which output audio in a non-standard way.
Fill Gaps: Adjust this to stop the stream when no audio is coming from the source, or to add Silence, Light Noise, or Heavy Noise to it. By default, Silence is added so that the connection to the AirPort Express is maintained.
Device Settings
Target Device: This allows you to select the specific device with which the source is associated.
Left Channel: For devices with more than two channels, you can select the channel which will serve as the left.
Right Channel: For devices with more than two channels, you can select the channel which will serve as the right.

Advanced Device Controls

This window allows Advanced Device options. To access it, select Advanced Source Settings... in the Audio menu when an audio device is set as the audio source. As above, most of these settings should be left at Default.

Input Device Settings
Device: Displays the device name selected in the main window for the input.
Left Channel: For devices with more than two channels, select the channel which will serve as the left.
Right Channel: For devices with more than two channels, select the channel which will serve as the right.
Buffering: Adjusts the size of the audio buffer for the input, in frames. A larger buffer is less prone to skipping but has higher latency (delay), while a smaller buffer has lower latency but may be more prone to skipping. This is best left at Default to start.

Output Device Settings
Device: Displays the device name selected in the main window for the output.
Left Channel: For devices with more than two channels, select the channel which will serve as the left.
Right Channel: For devices with more than two channels, select the channel which will serve as the right.
Buffering: Adjusts the size of the audio buffer for the output, in frames. A larger buffer is less prone to skipping but has higher latency (delay), while a smaller buffer has lower latency but may be more prone to skipping. This is best left at Default to start.

Debugging

The Debugging dialog can be accessed by holding down the option key as Airfoil launches. If a problem occurs, these debugging options may help show what's wrong.

Hidden Preferences
registrationObscured: This preference controls the visibility of the registraion code in the Registration window. If you're in a group environment, you may wish to obscure this code to prevent theft.
The example command below for the Terminal will cause the code to be obscured in the Registration window.
defaults write com.rogueamoeba.Airfoil registrationObscured NO