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What essentially is the difference between MPEG2 and DVD?

 
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Interkot



Joined: 09 Nov 2005
Posts: 1

PostPosted: Wed 9 Nov 2005, 23:58    Post subject: What essentially is the difference between MPEG2 and DVD? Reply with quote

Besdides the question in the subject, there is something I can not understnad either, some help is appreciated:

I take a DVD-video disk, pick a VOB file on it, copy it to my hard drive, check the size, it reports 0.99 GB

I start a DVD authoring software like Nero Vision Express 2, create a new
DVD project, add this file from the hard drive - the program reports
it will take up 1.19 GB

Why is there a size increase?
The same result with other authoring software I use
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Thu 10 Nov 2005, 5:45    Post subject: Reply with quote

VOB files are like any other file; simply a sequence of bytes. The size of the file will not change depending on where it's recorded. However, two things can cause the size to be different.

First, there is the fact that Windows considers that one kilobyte is 1024 bytes, one megabyte is 1024 kilobytes, and so on, while some software (and most hardware) considers that one kilobytes is 1000 bytes, one megabyte is 1000 kilobytes, and so on. If you look at the size in bytes it should be identical.

And second, when you add a video file to a disc using an authoring program, that program will automatically create a few other "control" files, and may alter some aspects of the video file, to make it compatible with the new disc's structure. In other words, the authoring program is reporting the space that will be taken up when the file is recorded, and not the actual current file size.

As to DVD and MPEG2, they are fundamentally different things. A DVD is a kind of optical disc, MPEG-2 is a video compression algorithm. Specifically, discs that conform to the DVD Video standard are DVD discs with a certain file structure, where the video is encoded in MPEG-2, within certain parameters (ex., only certain resolutions, frame rates, and bitrates are allowed, otherwise the disc does not comply with the DVD Video standard, and will not play correctly in set-top players).

RMN
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