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EDITOR’S NOTE: This article is an excerpt from The Macintosh iLife ‘05 , by Jim Heid (2005; reprinted by permission of Peachpit Press/Avondale Media).

For many iDVD projects, one click of the Burn button is all it takes to commit your work to plastic. But if you have a slow computer or a complex project, or just seem to have trouble burning reliably, you may be better off taking a more circuitous route. In iDVD 5, part of Apple’s $79 iLife ’05, you can create a disc image of your DVD project—which you can then use to test for errors or to access advanced burning options.

If you’ve downloaded software from the Internet, you’re probably already familiar with the concept of disc images. A disc image isn’t a disc or an image. It’s a file on your hard drive. The bits and bytes in this file are organized in the same way that they would be on a disc. If you double-click on a disc-image file, the Mac’s Finder reads the disc image and creates an icon on your desktop, as if you’d inserted a disc.

When you create a disc image in iDVD 5, the program performs the same steps as when you click on the Burn button, with one exception: after iDVD finishes preparing your DVD’s assets, it doesn’t fire up your DVD burner. Instead, it simply saves the data in a file on your hard drive—as a disc image.

Creating a disc image can be a great way to increase your success rate when burning DVD projects. Separating the encoding and burning processes into separate phases gives you more flexibility—and, often, more reliability.

Creating a Disc Image

To turn your project into a disc image, choose Save As Disc Image from the File menu (Command-shift-R). Give your disc image a name and click on Save. iDVD compresses your video, encodes your menus, and then saves the resulting data in the disc-image file. The file’s name ends in .img.

Testing a Disc Image

If your DVD has a lot of menus, transitions, and content, you should take it for a test-drive before you burn it to disc. To test your DVD, use OS X’s DVD Player program.

Double-click on the disc image file to create an icon on your desktop. If you double-click on this icon to examine its contents, you’ll see two folders: AUDIO_TS and VIDEO_TS. (If you added DVD-ROM content to the DVD, you’ll see a third folder, too.) Those awkward names are required by the DVD standard, as are the even more awkward names of the files inside the VIDEO_TS folder. (The AUDIO_TS folder will always be empty, but don’t try to create a DVD that lacks one; the DVD may not play in some players. And in case this ever comes up in a trivia contest, TS stands for transport stream. )

Start DVD Player and choose Open VIDEO_TS Folder from the File menu. Navigate to your disc image, select its VIDEO_TS folder, and click on Choose. Now press the spacebar, and your faux DVD will begin playing back.

Burning a Disc Image

If you found a problem when testing your disc image—a typo, for example, or a missing piece of content—you haven’t wasted a blank DVD. Simply trash the disc image, make your revisions in iDVD, and then create and test another disc image.

And if your disc image tested perfectly and you’re ready to burn? Don’t bother with iDVD’s Burn button—use the disc image instead.

Using Disk Utility
First, start up OS X’s Disk Utility program. (It’s located in the Utilities folder within your Applications folder.) Next, click on the Burn button in the upper left corner of Disk Utility’s window. In the resulting dialog box, locate and double-click on the disc-image file. Disk Utility then displays another dialog box. Before you click on its Burn button, select the little down-pointing arrow to expand the dialog box and see additional burn options.

You can get more-reliable burns—and increase the chances that your DVD will play in other players—by setting the Speed option to your drive’s slowest speed (see screenshot).

Need it quick? If you deselect Verify Burn, your disc will be ready sooner. On the downside, you won’t know if data was written inaccurately until you try to play the disc.

Other Ways to Burn
If you have Roxio’s Toast 6 Titanium ($100), you can drag your disc image’s AUDIO_TS and VIDEO_TS folders into Toast and burn the disc there. If you’ve installed Toast’s Toast It shortcut menu, the job is even easier: control-click on your disc-image icon and choose Toast It from the shortcut menu. (Use Toast’s Preferences command to install the Toast It shortcut-menu plug-in.)

You can also use Toast to fine-tune any DVD-ROM content you’ve added—for example, removing the raw versions of the photos you’ve included in a slide show.

Toast also gives you a choice of burning speed. For critical projects where you need the broadest compatibility, burn at 1x speed.


When you’re burning a DVD, avoid running complex programs that put a lot of demands on your system. For example, recording a track in GarageBand while burning a DVD isn’t a good idea. Also consider turning off file sharing and quitting any disk-intensive programs.

[ Contributing Editor Jim Heid publishes more iLife tips on his Web site. ]

To give your DVDs the widest compatibility and to get more-reliable burns, burn discs at your drive’s lowest speed.
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