DVD and CD are almost the same on surface, but they are difference inside. Assembled by single side/double side and single layer/double layer, DVD can be divided in to four basic physical structures: single side single layer, single side double layers, double-side, single-layer, double-side double layers. Single-sided DVD disc may have one or two recording layer. Like with the CD, CD-ROM laser from reading the following data on a single disc, double-sided DVD, the data were stored in the disc up and down both sides.
This refers to the common single-sided single-layer DVD discs, with a total capacity of 4.7GB, can store 133 minutes of video data.
Single-sided single-layer DVD disc is a blank substrate and a data recording layer of the substrate bonding layer formed. Both single-layer disc or a dual-layer disc by bonding two substrates made of the thickness of the substrate per tablet are 0.6mm, so DVD disc thickness 1.2mm.