What is a DVD?

To answer this question as simply and succinctly as possible, let's first separate out the physical format from the logical format. Pysically, a DVD is an optical disc format for storing data, and was invented in 1995 by Panasonic, Sony, Toshiba and Philips. It is kind of like a fat CD-ROM and can contain anything you want it to up to 4.5GB on a single layer. There has been lots of debate over the meaning of "DVD". It originally was referred to as a "Digital Video Disc", but now is universally accepted as "Digital Versatile Disc".

Logically, it usually has a UDF (universal disk format) file system. To put it in simple terms, think of this as the lines on a football field (indicating the yardage markers, the endzones and how the players know where to stand), although it could be specifically formatted for a different file system like Mac OS X Extended or ISO 9660.

A DVD Video Disc is specifically multiplexed mpeg 2 streams (audio and video) written in a specific format for DVD player software to decode and execute instructions like those in the menu, pertaining to first play when the disc is inserted, or where the split is on a dual layer disc. Think of these as the rules and the players on our UDF-formatted football field. An AUDIO_TS folder is part of the original specification and some DVD players may fail if this folder is not found on the disc (even though there is nothing in the folder). A DVD also has a VIDEO_TS folder in its root or top-most directory. Inside of it, there are 3 types of files: VOB files contain the various multiplexed video streams, IFO files contain the actual instructions that tell a DVD player and its remote what to do, and BUP files contain backups of the IFO files in case of corruption.

As far as the DVD player is concerned, think of it not as a glorified VCR or CD player, but more like a cheap computer that has a DVD-ROM drive, a video card and some software on a chip that decodes the above VIDEO_TS folder. Many DVD players are also capable of playing MP3 files, audio CD and photo jpeg files, but for this article, we are only discussing DVD Video.

A DVD disc can be used as a giant CD-ROM (formatted with UDF, but containing native video files, PDFs, software, etc.). In other words, it can also contain data meant only for a computer since a DVD player only looks for the VIDEO_TS folder. This means that PDFs, weblinks, or a computer program, for example, could be added to a separate folder in the root directory (really useful for trainging manuals and materials).

Before you get your next DVD burning project under, but sure to check out our large selection of blank DVD-R media. We carry professional brands from JVC Taiyo Yuden, Falcon Media, Verbatim, MBI Pro, among others.