Monday, February 27, 2006

Dual Disc: a Second Look.

It has been over a year since I last posted. But here’s an update on the Dual Disc format. What I said earlier is only half the story. True, Dual Disc has two sides, but it’s a lot closer to a dual-layer disc than a double-sided disc.

Here’s why: the two disc formats are placed back to back, but about as close as two layers of a DVD. This differs physically from the double-sided DVD, which is thicker because it is two discs, essentially, glued to each other, whereas Dual Disc is no thicker than an ordinary CD. So now I know what took them so long to come out with it in the first place!

There’s also a reason why the CD data must be on an opposite side. Unlike SACD, which was designed with the capability to support a hybrid format, DVD technology has been ever changing and updating. Nearest I can figure, if CD and DVD were put on different layers of the same side, most existing players would only be able to play the CD layer, and would ignore the DVD data entirely. To avoid this, Dual Disc was designed as a flip-side, rather than dual-layer, format. So yes, we still have to put the correct side in the player; and yes, there are no labels on Dual Discs. But this is the price you pay for backward compatibility.