There are two physical dimensions: 12cm (4.7 inches) and 8cm (3.1 inches) in thickness are 1.2mm, consisting of two 0.6mm thick adhisive backing layer. This is the same with CD. DVD disc can be a single or two-caced. Each face can have 1 to 2 data layers. Disc capacity is determined by the size of audio with video, as well as how the video and audio are compressed. The 133 minutes which was often reffered is not true: Only one channel of the DVD can store 160 minutes, if the compression quality are as VCR, then a data layer of DVD can store nearly 9 hours of video and audio.
In the average rate of about 4.7Mbps case (3.5 Mbps for video, 1.2 Mbps for three 5.1-channel soundtracks), a single-layer DVD can store a little more than 2 hours of data. A 2-hour movie , if there are three tracks, the average data rate is 5.2 Mbps. If a Dual-layer DVD’s average data rate is 9.5 Mbps (very close to the 10.08 Mbps limit), it can also store 2 hours of video.
If the main data of a DVD-Video disc is audio, and use 48kHz/16-bit PCM (slightly better than CD quality), then will be able to store 13 hours of audio (for dual-layer disc can store 24 hours). If you use a single 64kbps -channel Dolby Digital, you can store 160 hours of audio (dual-layer disc will be able to save 295 hours).
Store CD-ROM can be 650 trillion bits of data, which is 0.64 gigabytes or 6.8 billion bytes. In the following list, SS / DS, said single / double-sided, SL / DL / ML said the single / double – / mixed-layer (mixed layer is a surface layer of the disc, and the other side there are two layers), gig is a Gigabit (2 ^ 30), BB said that one billion bytes (10 ^ 9). See giga and billion 7.2. （To be continued…）by: DVD copy 2012