Thread: DVD Media

DVD is an optical disc storage media format that can be utilized for storing data, admitting movies with high video and sound quality. DVD resemble compact discs their physical proportions are the similar 12cm or the minimize 8cm but they are encoded in a unlike format and at a much higher spacing. Unlike CD, all DVD must include a file system. This file system is called UDF, and is an extension of the ISO 9660 Standard used for Data-CD.

DVD are created from a 0.6 mm short disc of polycarbonate plastic surfaced with a much thinner aluminum layer. Two this discs are pasted together to form a 1.2 mm double-sided disc. The basic DVD disc is thinner than a CD to make itpossible to use a lens with a higher numerical aperture.

A single-layer DVD can keep 4.7 Gbyte, which is about seven times more than a standard CD-ROM. By applying a read laser at 650 nm (was 780 nm) wavelength and a mathematical aperture of 0.6 (was 0.45), the read-out resolution is increased by a factor 1.65. This holds for two dimensions, so that the genuine physical data density additions by a factor of 3.5. DVD uses a more effective coding method in the physical layer. CD's error punishment, CIRC, is substituted by a powerful Reed-Solomon product code, RS-PC; Eight-to-Fourteen Modulation (EFM) is changed by a more effective edition, EFMPlus, which has the same features as classic EFM. The CD subcode is removed. As a result, the DVD format is 47% percent more effective with respect to CD-ROM, which uses a 'third' error correction layer.