April 24, 2006

Image to Disk
Creating a Disc Image in DVD Studio Pro and iDVD for burning to DVD.

By Ken Stone

When you have finished authoring your DVD project in either DVD Studio Pro or iDVD you can complete the process by clicking on the 'Burn' button. But there is another way to burn your DVD that offers some advantages over the simple 'Burn' button.

DVD Studio Pro

Both DVD Studio Pro and iDVD allow us to create a 'Disc Image'. A Disk Image is a computer file that has the complete structure, format and content of a physical disk, CD or DVD, minus the plastic. It is a 'virtual' disk and behaves in the exact same way as a physical disk. Your Mac won't know the difference. So why would we want to create a disc image first before burning, as opposed to just burning straight away? In DVD Studio Pro and iDVD we can preview or simulate our DVD; a remote control opens up on screen and we can run the links and check out our DVD. However, the key here is the word 'simulate', which is what DVD SP or iDVD is doing, simulating what it thinks the finished DVD will be like. The problem is that the simulation is working with the raw files (video, photos, etc) that we have supplied it with, which are very different from the files that exist on a finished DVD after it has been built, formatted and encoded. It is still a good idea to simulate or preview your DVD, as there is the opportunity to catch errors early on, but just because the DVD seems to work properly in simulation, you can still burn coasters. This is where the disc image comes in, as a disc image is the finished product, and can be tested in the Apple DVD Player. This is a real world test of your finished DVD and is much more accurate way to test.

In DVD Studio Pro, to create a disc image, click on the 'Build and Format' button or from the menu bar > File > Advanced Burn > Build and Format.


In the Build and Format window, near the bottom is the 'Destination' section. In the Output Device menu select 'Hard Drive'. When Hard Drive has been selected you will notice that the 'Output Format' option now reads .img (this is our disc image).


When you click on the Build and Format button the process begins and you will first be presented with a progress bar. When completed, a Formatting Successful box will appear.


Your DVD disc image now appears on the Desktop.

In iDVD (versions 5 and 6), to create a disc image, select 'Save as Disc Image' from the File menu. You will then be asked to name and Save the disc image.


When the process has been completed, a dialog box will tell you that Burning is finished, Disc image created. The disc image will appear on your Desktop.


I should point out that a disc image can exist in two different states. The disc image (.img) as it first appears on the Desktop, is the disc image 'file', the virtual DVD (left side). When we double click on this icon, we mount or open the disc image (right side), making it available for use with the Apple DVD Player.

Now that we have our disc image we can use it to test our DVD. Open the Apple DVD Player, with the DVD Player open double click on the disc image to mount it. This will cause two things to happen, first a folder will open on the desktop with two folders inside, AUDIO_TS and VIDEO_TS, go ahead and close this window and, second, it will load the disc image into the DVD Player ready to be played.

Now, as you test out your DVD you will be testing a 'real' DVD as opposed to simulating it.

When you are satisfied that everything is working properly, it is time to commit to plastic. Open Disk Utility and look in the left hand column in the Disk Utility window. If your disc image is mounted you will see two items, the disc image and the mounted version, as shown below. It is not necessary to mount the disc image for burning and, if it is unmounted, then only the disc image will be listed in the left column. Either way, you will want to select the disc image. With the disc image selected, the Burn button, in the Disk Utility tool bar, will become active. Should you select the mounted version, the Burn button will be grayed out. We want to select the disc image.

After clicking the Burn button the Burn Disk window will open.

If you have more than one DVD burner you can select which burrner you want to use.

Burning using Disk Utility offers us a choice of burn speed. In this example my blank DVD is a 8x, but my burner is only a 4x, so 4x is the fastest option available. Even if you have the ability to burn at faster speeds, it is generally accepted that slower burn speeds help with reliability when the finished DVD is played in older players. The slower the burn speed, the more reliable the DVD. We are also offered the option to have the burnt DVD 'Verified'. This process matches, bit by bit, the data on the burnt DVD with the disc image. Verification will happen at the fastest read speed of your burner.

When you have successfully burnt your DVD, you can delete the DVD Studio Pro or iDVD project and keep the Disk Image if you think that you might need to burn additional copies. Even if you delete the disc image, they can be quite large, if you have a copy of the physical DVD, you can create a new disc image from the DVD and burn extra copies. When you are done and no longer need the mounted version of the disc image, control click on it and select 'Eject' or drag it to the trash to unmount.

I have found that Tigers Disk Utility is very robust and offers options not available in DVD SP and iDVD. Being able to test a disc image in the Apple DVD Player before burning really cuts down on the number of coasters.




copyright © www.kenstone.net 2006

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