What Is a Digital Video Disc?

DVD digital video disc is not only used for film and television entertainment, but also used in multimedia computers and other fields.

DVD: Many people still regard DVD as the abbreviation of Digital Video Disc, or "Digital Versatile Disc". ^[1]

In the early 1990s, the U.S. Film Industry Advisory Board drafted a letter of wish on behalf of the seven major Hollywood film production companies, one of which was to require a standard length (135 minutes) video to be recorded on a CD Programs and require higher image and sound quality than LD. It is important to know that the video resolution of a VCD is only 352 × 240 (NTSC) or 352 × 288 (PAL). Obviously, the video performance cannot meet the above requirements. In view of Hollywood Film Group's influence in the world's entertainment industry, hardware manufacturers have begun new efforts. It can be said that this is the motivation for developing DVDs.

In the spring of 1994, an organization formed by the seven major movie companies in Hollywood, "HDVAGroup", considering that digital high-definition television will gradually become popular in homes, and home-based digital high-quality movies will have a huge market. Potential, so joint initiatives.

at the same time,

The most common DVD, that is, a single-sided single-layer DVD, has a data capacity of about 7 times that of a VCD. This is because the DVD and VCD use the same technology to read data hidden in the disc (optical reading technology). , But because the optical spot produced by the DVD's optical pickup head is small (the original 0.85m read spot size was reduced to 0.55m), so on the same size disc area (the appearance size of DVD and VCD is The same), the density of DVD data storage can be increased, that is, the increase in DVD data capacity can be said to be thanks to the progress of optical pickup heads.

Disc diameter: 120mm

Disc thickness: 0.6mm / side

Laser wavelength: 635-650nm

Numerical aperture: 0.6

Track pitch: 0.74m

Minimum pit length: 0.4m

Error correction code length: RS-PC

Modify the signal modulation mode: 8-16

Utilization rate of disc surface: 86.6 square centimeters

Bytes per sector: 2048-2060 bytes / sector

According to its purpose, it can be divided into 5 types:

DVDVideo: for watching movies and other visual entertainment. If double-sided and double-layered on each side, the total capacity can reach 17GB.

DVD-ROM: The basic technology is the same as DVDVideo, but it includes a computer-friendly file format. Used to store data.

DVD-R: Its capacity is 4.7GB. In fact, it is used for professional creation and general users. Users can write to DVD-R only once.

DVD-RAM: This allows the DVD to be used as a virtual hard disk with random access. The original was a 2.6GB drive, and the capacity could be increased to 4.7GB per side. Can be rewritten 100,000 times.

DVD-RW: Similar to DVD-RAM, but with sequential read-write access, more like a record player than a hard disk. The read and write capacity of each side is 4.7GB.