Rogue Amoeba has rolled out Airfoil 4 (http://www.rogueamoeba.com/airfoil/mac), an upgrade to the tool for streaming audio around the house.

Originally designed to send any audio to Apple's Airport Express router (which supports only iTunes by default), Airfoil has grown to support streaming to the Apple TV, as well as other
computers running Airfoil Speakers (on Mac OS X, Windows, and Linux), and even to iOS devices such as the iPhone, iPad, and iPod Touch.

The Airfoil 4 update starts with an update to Airfoil Speakers, which enables you to receive audio on other computers in your house. Just run Airfoil Speakers, and Airfoil will send audio from your Mac to any machine on your network.

With version 4, Airfoil Speakers can initiate a connection back to Airfoil, so you can tune in to audio without dashing back to the Mac running Airfoil. What's more, Airfoil Speakers offers remote control of selected sources, including iTunes and Pulsar. Pause playback, or skip tracks, from across the room or across the house.

Airfoil Speakers also features an updated interface, which shows metadata about the audio being played, including track information and album artwork when available. There are also new level meters and the remote controls.

Airfoil Video Player, the second of Airfoil's companion applications, has also received an update with version 4. Using Airfoil Video Player, you can watch video on your Mac while audio plays through any remote speakers, all in sync. It's always supported local files and DVDs, but this upgrade brings support for watching web video as well.

Airfoil 4 also offers other improvements, from a streamlined interface to better audio grabbing from applications like Google Chrome, as well as all System Audio. And when the new crop of
third-party AirPlay receivers from companies like iHome and JBL finally arrive, Airfoil 4 will be ready to support them as well, according to the folks at Rogue Amoeba.

Airfoil 4 is optimized for, and exclusively available on, Mac OS X 10.6 ("Snow Leopard"). A free trial is available for download, and new users can purchase Airfoil through the Rogue Amoeba online store for US$25. Owners of older versions of Airfoil can upgrade for $10. While in its trial state, Airfoil will overlay noise on all transmissions longer than 10 minutes.