The Science of DVDs: Structure, Encoding, and Playback

Physical Composition
Physical Composition
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 Encoding
Data Encoding
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.
Laser Technology
Laser Technology
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.
Storage Capacity
Storage Capacity
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.
Compression Techniques
Compression Techniques
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.
Regional Coding
Regional Coding
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.
Beyond Video
Beyond Video
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.
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What is a DVD's base layer made of?
Aluminum
Polycarbonate
Protective lacquer