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VOB - MPEG2 Files on a DVD - What Are They?

written by: Bobby Freidin•edited by: Rhonda Callow•updated: 3/5/2010

The DVD has definitely become the new standard in video. Let’s take a look at the file structure that makes a DVD work.

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    Introduction

    VOB is simply shorthand for “Video Object” and is the standard file type used in DVD authoring. A VOB file is a strict implementation of an MPEG-2 (Motion Picture Experts Group Phase 2) video stream. That doesn’t help much does it? MPEG-2 is simply a revision standard for video files. We need to have standards for our files so that we can design different video editing software and hardware to view these files. Mainstream standards such as the MPEG series could be a combination of many years of negotiation between different media companies.

    While MPEG-2 files normally just contain a video and audio source, VOB files have an extra stream for subtitles. VOB files also allow a DVD to be authored with what is known as “multi-angle streams.” For example, they could allow you to switch between different perspectives while watching a movie. It’s expensive and time-consuming to shoot a movie several different times, so we don’t see this feature implemented very often.

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    What's on a DVD?

    Take a look at image 1 below and you’ll see an example of the contents of a DVD disc. Notice every VOB file is 1 gigabyte (1000 megabytes). This is done out of convenience for various operating systems that cannot tolerate large files. Sometimes VOB files are not split by the gigabyte and are split by every chapter in the DVD menu. DVDs also have IFO files which give the player instructions on how to handle the DVD. BUP files are backups of these IFO files.

    There are many digital editing software programs available on the web that allow you to copy the VOB files to your hard drive and convert them to various video files. Most new DVDs are made with copy protection schemes that encrypt the files. More often than not, hackers are able to break the encryption scheme and there is a great deal of controversy over the whole concept of media protection since incidents such as this scandal with Sony.

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    So What Now?

    Well, with a quick Google search you will find programs that can help you archive your DVD collection to a computer system. Some will even get past copy-protection schemes, stating a "do at your own risk" policy. Copying the contents of a DVD to your computer’s hard drive allows you to play the DVD without using the disc. The legal argument for consumers is usually that this can allow storage of the original DVD disc without scratching it. Media companies think any type of copying will lead to digital pirating. Besides legal issues, there is one other problem with digital DVD archiving - an average DVD is over 4 gigabytes in size, and with only a handful of DVDs you can fill up your hard drive to its maximum capacity very quickly.

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    Images

    Sample DVD Structure