The company says that the Turbo.264 accelerates exports by a factor of four on an Intel Core 2 Duo up to a factor of 10 on a Power PC G4. In other words, the rate of acceleration depends on the Mac processor type. The Turbo.264 is designed to offload the computationally intensive software conversion of video files away from your Mac, leaving it free for other tasks. It supports all Macs with USB 2.0.
Turbo.264 comes with video conversion software by Elgato. You can drag-and-drop videos into the application and chose one of these formats: Apple TV (800 x 600), iPod High (640 x 480), iPod Standard (320 x 240), iPhone/iPod touch (480 x 360) Sony PSP (320 x 240, but with a 160 x 120 thumbnail image) and YouTube (320 x 240). The hardware/software also works with EyeTV. EyeTV 2.4 or later will automatically detect the Turbo.264, if it's attached to your Mac. Then, if you choose certain H.264 export options in EyeTV, the Turbo.264 will be used to accelerate the export.
Installation is a breeze. Plug in the USB stick and drag the Turbo.264 application off the accompanying CD. The first time the app is launched, it automatically installs the necessary QuickTime plug-in code to link the multimedia software into the Turbo.264 hardware, and after an optional registration process you can start encoding video.
In order to use the Turbo.264 your Mac needs: a PowerPC G4, PowerPC G5 or Intel Core processor, 512MB of RAM, built-in USB 2.0 port, Mac OS X 10.4 (or later). Also, make sure you have the latest versions of QuickTime and iTunes.
The Turbo.264 is a no-brainer to use. Drag one or more movies files onto the onscreen icon, and they're listed in the order in which they'll be converted. The level of acceleration depends on the size of the output. During the encoding process, you can watch the status via time remaining and frame rate readouts.
Turbo.264 supports DVD chapter markers, and enables you to pick from multiple audio tracks. It can also preserve Dolby Digital audio when encoding to Apple TV format so you can play back video on your Apple TV with your multi-channel audio sound system. Turbo.264 supports the transcoding of entire transport streams, for example from set top boxes, and automatically detects widescreen DVD content to encode it without black bars.
The Turbo.264's QuickTime connection means you can encode video in a variety of applications. The Turbo.264 supports batch conversions and offers exports of unprotected DVD content (VOB files). It also accelerates exports from such Mac applications as iMovie, QuickTime Pro, Final Cut Pro, and EyeTV. Turbo.264 software installs profiles into iMovie, which means you can choose the predefined formats from directly within the iLife component and take advantage of the hardware acceleration.
The USB stick also offers the ability to do things such as dragging a DVD's video_ts folder over and converting its video contents (if they're not encrypted). Unfortunately, you can't choose specific chapters and titles from a DVD to rip. The "feature presentation" is all you get. What's more, I also found that in encoding decrypted DVDs, sometimes the Turbo.264 would sometimes fail about one-half to one-third of the way through.
The time savings are nice, but not huge, if you have a new Mac. On my 24-inch iMac (with a 3.06GHz Intel Core 2 Duo processor) I downloaded the movie trailer for The Incredible Hulk and encoded it with and without the Turbo.264. With Elgato's hardware/software combo the encoding took: Apple TV (165 seconds), iPod High (134 seconds), iPod Standard (95 seconds) and Sony PSP (96 seconds). Without it, the encoding results were 805, 548, 349 and 389 seconds, respectively.
Owners of older Macs, G5's as well as G4's, will see much faster compression times. However, even beyond the speed savings, there is an advantage with the Turbo.264 in that your Mac is more-than-usable while encoding video as the Elgato device assumes much of the heavy lifting.

Conversion to H.264 results in files smaller than the original, which makes the Turbo.264 useful for folks like me who are digitizing their old VHS tapes for burning to DVD and need to make backup copies that don't overwhelm my available storage. Previously, I was unhappy that you couldn't make your own custom compression settings. But as of version 1.1, you can. To access the new custom settings dialog, add a source movie to the Turbo.264 application and click on the Format drop-down menu. Choose Edit from this menu. 

However, I do wish the Turbo.264 supported more apps, especially [url=http://www.macsimumnews.com/index.php/archive/review_handbrake_a_rippin_good_app_for_5g_ipod_owners]Handbrake[/url], a multithreaded DVD to MPEG-4 ripper/converter.
Finally, the results of encoding turn out slightly darker than the originals, but not drastically so.
Turbo.264 costs US$99.95. The package includes the USB 2.0 Hardware Encoder, the Turbo.264 software on CD-ROM, a user's guide on CD-ROM, a quick start guide as well as a USB extension cable.
Macsimum rating: 8 out of 10.