What is a DVD? What is the DVD format?

The full English name of a DVD is digital video disk, which is a digital video disc or digital photo disk. It uses MPEG2 compression technology to store images. It is also called digital versatile disk, which is a digital multi-purpose disc. It integrates computer technology, optical recording technology, and film and television technology, its purpose is to meet people's needs for large storage capacity and high-performance storage media. DVD discs have been widely used in audio/video fields, and will drive the development of publishing, broadcasting, communication, WWW and other industries. It is widely used and can be seen from the five specifications it has set:

DVD-ROM-Computer Software read-only disc, similar to the use of CD-ROM;

DVD-Video: A home audio and video CD. Its usage is similar to lD or video CD;

DVD-audio-a music disc for usage similar to music CD;

DVD-R (or DVD-Write-once) -- a single-write DVD for usage similar to a CD-R;

DVD-RAM (or DVD-rewritable)-a disc that can be read and written multiple times for usage similar to Mo.

From the following aspects, we can see that the DVD is better than CD and VCD:

1. Large Capacity and fast reading: Most of the DVDs share the same size as general CDs, with a diameter of about 12 cm (or 8 cm ), it is pasted by a base material of 6mm mm in thickness. It adopts multi-faceted multi-layer technology, that is, each disc can store dual-layer information, and a single disc can store up to four sides of storage space, DVD improves the storage density per unit area by focusing on a more concentrated red laser, so its storage space is unprecedented (Table 1) sort out the storage capacity and applicable specifications of different storage forms. In addition, the maximum read rate of a single-layer DVD is 11.08 Mbit/sec, which is equivalent to an optical disc machine with a speed of eight times.

2. High-resolution video: a dvd using MPEG2 standard image compression technology. Its resolution can reach 720 × 480, far exceeding 352 × 240 of VCD. MPEG2 has the ability to elastically adjust the video read rate, so it can save a lot of storage space while maintaining the original image quality. In addition, the built-in letterbox and pan and scan display modes of the DVD player can also adjust the aspect ratio of the TV at or.

3. High Fax sound quality: the DVD can use more precise sampling accuracy to convert analog information, and expand the traditional binary channel to 5.1 channels, so that people can truly enter the multi-channel world.

Physical format		120mm disk storage capacity (GB)	80mm disk storage capacity (GB)
DVD-ROM DVD-video	Single-sided single-layer Single-sided, Double-Layer Dual-sided single-layer Double-sided	4.7 8.5 9.7 17	1.4 2.6 3.9 5.3
DVD-R DVD-RAM	Single-sided, Double-Layer Double-sided Single-sided, Double-Layer Double-sided	3.9 7.8 2.6 5.2	1.2 2.4 0.7 1.4