DVD players decode MPEG-2 encoded movies.

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You hit the button to open the tray on your DVD player, nestle your disc into place, let the tray glide into the box and -- boom -- "Mary Poppins" starts. But what manner of digital magic is employed to make Mary and Bert and the Banks children sing and play on your TV screen? Of course, it's not magic at all, but it is a feat of engineering and technology.

A DVD player is very similar to a CD player, with a laser assembly that shines the laser beam onto the surface of the disc to read the pattern of bumps (see How CDs Work for details). The DVD player decodes the MPEG-2 encoded movie, turning it into a standard composite video signal (see How Television Works for details). The player also decodes the audio stream and sends it to a Dolby decoder, where it is amplified and sent to the speakers.

The DVD player's job is finding and reading the data stored as bumps on the DVD. Considering how small the bumps are, the DVD player has to be an exceptionally precise piece of equipment. Learn more on the next page.