What is DVD?
A DVD looks just like a CD except that it can store larger amount of data than a CD. Both have same diameter and even same thickness too. However, a DVD has more data storage capacity due to its different data storage technique. Most DVDs use single side for data storage and data is stored on a single layer. When compared with CDs, they can store more than six times of data, although multi-layer DVDs are also available. What makes DVDs so different from CDs or VHS tapes, is their use of the compression method (MPEG-2) to store a complete movie in HD video format with Dolby digital surround sound features.
DVD and VHS
DVD is the acronym for Digital Versatile Disc. Any kind of data like computer files, audio and video can be stored on a DVD. In a DVD, the information is stored as pits on the disc and a rotating laser head reads the data.
VHS is a magnetic tape and the data which is recorded on the tap is read by a moving sensor in a VCR.
A DVD can provide higher resolution (720 pixels horizontally) while VHS has just half of this capacity. Thus, a DVD picture is much sharper and the colour element is much more vivid.
While VHS can show only pictures of the standard 4:3 aspect ratio, DVD is compatible with both standard and widescreen 16:9 aspect ratios. This makes DVD is suitable for High Definition videos which are usually produced in 16:9 screen mode.
DVD usually comes with Dolby Digital surround sound features which provide true theatrical experience to the users when a DVD is used with HDTV and Home Theatre system. DVD also has multiple soundtracks so movies on DVDs provide subtitles and soundtracks in more than six languages.
With a DVD, you can easily access any part of the video just by going to the main menu where you can select the part you like to watch. However, with a VHS player, you have to fast forward or rewind to access a specific part of a video.
DVD movies usually come with menus that help you to access the specific sound track, subtitle and other features. By contrast, VHS can not provide these sophisticated features.
DVD and CD
DVD differs from CD due to their huge data storage capacity, data encoding methods and other features.
Although single side DVDs are common and inexpensive, double side DVDs are also available. In addition, a DVD can store data on two layers on each side. These storage methods make DVD to have data storage capacity up to 15.9 GB.
On a DVD, the pit size and pit length are much smaller (more than two times smaller) when compared with a CD. So, a DVD has space for more than six times of pits and tracks that a CD can accommodate. While this is one of the reasons for their huge capacity, the data error correction methods used by a DVD require less space leaving more free space for data storage.
Unlike CDs, DVDs come in different formats. Single sided or doubled sided. Each side can have up to two layers, thus a double sided and double layer DVD will have more than 12 GB capacity and you can play it for over 7 hours.
