DVD Creation for the Rest of Us
By limiting the available video time to one hour and by encoding only at a high constant bit rate (8Mbps), Apple provides a great picture that users can’t degrade (except with bad source material, of course). Professional DVD authoring packages squeeze more time onto a standard disc by pre-filtering, pre-examining, and then encoding at a variable bit rate. This can take up to 24 times viewing time to accomplish. iDVD's constant bit rate encoding, on the other hand, requires no pre-filtering and results in a very high quality image. In my tests, I encoded material from a DV camera, a transfer from a SuperVHS tape, and some lower quality older VHS material. Not once did I observe a decrease in the picture quality, though in the case of the lesser quality source material the "garbage in/ garbage out" rule definitely applies.
Another advantage of this one-hour limit is speed. Because there is no pre-filtering or look-ahead cycles, and also because iDVD is configured to take advantage of the G4 processor’s AltiVec engine, the encoding time in my tests was only 1.5 to two times viewing time. Including the time for actually burning of the disc, from the time I hit the "Burn Disc" button to the finished product was about 2.5 hours for a DVD containing one hour of video.
According to Apple, this time will be reduced even further with iDVD 2, which will only be available for OS X, as the OS X platform will allow encoding in the background as the disc is being built. In addition, the maximum video time available on the same 4.7GB disc will be increased to 1.5 hours — albeit with a hit in quality for discs over 60 minutes in length, as the program will shift to a lower (5.5Mbps) encoding rate.
Not Just for Movies
The ability to place thousands of still images on a DVD opens up a lot of potential for iDVD to be used as a portfolio distribution system by graphic artists and photographers. A disc can contain thousands upon thousands of images arranged as slideshows, although each slideshow can contain a maximum of 99 images, and each menu can only contain six buttons, so each menu can have access to 495 images plus a button for the next menu. My test disc for still images contained almost 1600 images, but used less than 5 percent of the available disk space.
There is a matter of RAM footprint that comes into play when dealing with such a high number of assets, however. I found that as I approached 200 or so images, iDVD began requesting more and more RAM to deal with it. One can assign a bigger RAM footprint to the program easily, but since the test computer ships with only 128MB RAM, this soon runs low for discs using large numbers of images. You can always increase the amount of virtual memory to get your RAM, but disk swapping naturally causes a performance hit. A much better solution would be to go RAM crazy and get 512MB of the stuff, which is pretty sweetly priced these days, and turn off virtual memory altogether.
For the professional DVD portfolio user, there is one very significant "gotcha": slideshow images, like undersized video movies, are automatically increased to the standard 640x480-pixel screen size. While the original aspect ratio is maintained, when viewed on a standard NTSC TV set, this results in some loss of image at the borders due to overscanning, which can vary from TV set to TV set. (This is not an issue with LCD screens, which show the entire image.) iDVD does include a "safe area" indicator that can be toggled on and off for preview purposes, but it can’t save things at "safe" resolution.
The workaround is to preprocess your images using the batch function in Photoshop to resize your "portrait" images to a maximum height of 440 pixels, and your "landscape" images to a maximum width of 600 pixels, then, superimpose the resized images onto a 640x480-pixel matte background. iDVD will see the matte as the image size and will not resize the processed images, so the full image can be viewed on a standard TV set.
The Bottom Line
Apple has come through with an authoring program that clearly meets the design goals of functionality, high quality and extreme simplicity. Most photographers and semi-pro video artists will find it’s well worth the workarounds imposed by its minimalist operation, though if you want to author Hollywood-style DVDs you will need to look at more sophisticated authoring packages.
If you already have a PC with muscle, you can buy a SuperDrive under its maiden name, the Pioneer DVR-A03, and choose any number of Windows programs that claim ease of use. With iDVD, it’s really about whether or not you want to buy a powerful Mac, since there’s no other way to get it. iDVD alone isn’t sufficient reason to go with a Mac, but if you’re fond of the other value Apple provides in its systems and you’re on the fence about a purchase, this might just tip you over onto the Cupertino side.