The Science of DVDs: Structure, Encoding, and Playback

Movie CDs, also known as DVDs, consist of multiple layers, including a polycarbonate base, reflective aluminum, a protective lacquer, and a label. Their structure allows for high-density data storage essential for video.

Data on a DVD is encoded in pits and lands - microscopic bumps and flat areas on the aluminum layer, representing binary code. A laser reads these variations to play the movie.

DVD players use a red laser at 650nm wavelength, finer than the infrared used in CDs, permitting greater precision and data capacity, crucial for storing full-length movies.

A standard single-layer DVD can hold 4.7GB of data, enough for a 2-hour movie at standard definition. Dual-layer DVDs double this capacity by adding a second data layer.

DVDs employ MPEG-2 compression to fit movies into limited space. This algorithm is efficient at reducing file size while maintaining perceivable quality, balancing the trade-off between space and video fidelity.

DVDs may include region codes, restricting play to specific geographical areas. This is a form of digital rights management to control content distribution across different markets.

Surprisingly, DVDs can carry more than movies. They often include multiple soundtracks, subtitles, interactive menus, and special features, all within the same disc, thanks to their robust storage.

The laser technology in DVDs originated from NASA's space communication systems, showcasing the unexpected crossover between space exploration and home entertainment.