How Flexplay DVDs Work

Normal DVDs

In most respects, a Flexplay DVD is just like any other DVD -- it has only one major addition.

The basic idea behind standard DVDs is very simple. The images and sound that make up a DVD disc are encoded digitally -- as bits of information (strings of 1s and 0s -- see How Analog and Digital Recording Works for more information).

The DVD manufacturers put all this digital information onto a disc as a pattern of "bumps" (raised areas) and "lands" (flat areas), arranged in a very long track, spiraled around the disc. The manufacturing machinery presses the bumps into layers of polycarbonate plastic and then sputters a reflective metal layer onto the plastic.

Unlike CDs, DVDs actually have two reflective layers -- an inner reflective layer, and a semi-transparent outer reflective layer -- with two different data tracks (so the disc can hold more information). The manufacturing machinery bonds the two layers together using resin adhesive, which hardens into solid plastic, securing the two sides into a single disc.

When you play a DVD, the DVD player shines a narrow laser beam over the data track. The laser hits the bumps and flats on both reflective layers, and the beam bounces back to an opto-electronic sensor (basically, a light reader). Because they are different shapes, the bumps and flats reflect light differently. The sensor detects the difference, reading the pattern encoded onto the disc. (See How DVDs Work for more information.)

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Flexplay's discs work exactly the same way, but they include a specialized layer of material in the disc, in front of the inner reflective layer. This layer is the key to the disc's limited play time, as we'll see in the next section.