DVD Media

DVD is an optical disc storage media format that can be used for storing data, including movies with high video and sound quality. DVDs resemble compact discs: their physical dimensions are the same—12cm or the mini 8cm—but they are encoded in a different format and at a much higher density. Unlike CDs, all DVDs must contain a file system. This file system is called UDF, and is an extension of the ISO 9660 Standard used for Data-CDs.DVDs are made from a 0.6 mm thick disc of polycarbonate plastic coated with a much thinner (reflective) aluminium layer. Two such discs are glued together to form a 1.2 mm double-sided disc. The basic DVD disc is thinner than a CD to make it possible to use a lens with a higher numerical aperture.A single-layer DVD can store 4.7 Gbyte, which is around seven times more than a standard CD-ROM. By employing a read laser at 650 nm (was 780 nm) wavelength and a numerical 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 actual physical data density increases by a factor of 3.5. DVD uses a more efficient coding method in the physical layer. CD's error correction, CIRC, is replaced by a powerful Reed-Solomon product code, RS-PC; Eight-to-Fourteen Modulation (EFM) is replaced by a more efficient version, EFMPlus, which has the same characteristics as classic EFM. The CD subcode is removed. As a result, the DVD format is 47% percent more efficient with respect to CD-ROM, which uses a 'third' error correction layer.DVD Media can contain: DVD-ROM (read only, manufactured by a press) DVD-R/RW (R=Recordable once, RW = ReWritable) DVD-RAM (random access rewritable; after-write checking of data integrity is always active.) DVD+R/RW (R=Recordable once, RW = ReWritable)Two DVDs with different bottom sides.The disc may have one or two sides, and one or two layers of data per side; the number of sides and layers determines the disc capacity.DVD-5: single sided, single layer, 4,704,317,440 bytes, 4.7 gigabytes (GB), or 4.38 gibibytes (GiB)DVD-9: single sided, double layer, 8.5 GB (7.92 GiB)DVD-10: double sided, single layer on both sides, 9.4 GB (8.75 GiB)DVD-14: double sided, double layer on one side, single layer on other, 13.3 GB (12.3 GiB)DVD-18: double sided, double layer on both sides, 17.1 GB (15.9 GiB)The capacity of a DVD-ROM can be visually determined by noting the number of data sides, and looking at the data side(s) of the disc. Double-layered sides are usually gold-colored, while single-layered sides are silver-colored, like a CD. One additional way to tell if a DVD contains one or two layers is to look at the center ring on the underside of the disc. If there are two barcodes, it is a dual layer disc. If there is one barcode, there is only one layer.Each medium can contain any of the above content and can be any layer type. Double layer DVD+R discs are already on the market.Provider Info: Cdrdvdrmedia.com Tel: 1-626-854-2145 Toll Free: 1-888-813-5667 Fax: 1-626-854-6553 Website: http://www.cdrdvdrmedia.comProfile about DVD Media(http://www.cdrdvdrmedia.com)Cn Rambler Cdrdvdrmedia.com

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