Would it be possible to convert Xvid to DVD again???

[AquaStealth]

Hello:)
I was thinking about all the possibilities of modern video technology
the other day and this question came to my mind:
Is it possible to use "reverse ripping" of a DVD to Xvid so that you
can decompress an Xvid-file and obtain a file of real DVD quality?

If you compare DVD ripping with Zip or Rar archiving you probably
understand better what I mean.
A zip file consist of compressed data i.e. a word document.
Because of the "logic" compressing rules of the zip program you can
decompress the zip file and obtain the originl word document exactly
the way it was before you archived it.

DVD ripping tools probably uses the same compressing rules everytime
you rip a DVD. This should mean that if you know what the original
DVD file looked like (i.e. resolution, fps and bitrate etc.) you
should be able to get the ripping software to work backwards and
transform an Xvid movie to a DVD movie again.

Comments from proffesionals in this area are more than welcome:)
Stay cool......as always/ AquaStealth

[Mug Funky]

Zip and Rar don't throw anything away.

Xvid and MPEG-2, however, throw away quite a lot. this is why you can compress so, so much more with them - imagine zipping LOTR from uncompressed YV12 master. you'd get a VERY VERY VERY large file :)

certainly, it is possible to convert an Xvid to DVD, however, it requires the mpeg-2 to be re-encoded from the Xvid (which was re-encoded from the DVD in the first place). each of these stages removes information that cannot be put back.

of course, the output would still be quite watchable - it's a testament to how good these algos are, and how bad TV and human visual system can be :)

[edit]

you can compare it to shorthand writing - it's a set of rules that allow the original text to be re-created perfectly. however, if you were to take a passage of english, translate it to japanese, then go back to english, it'll come out very, very different. the meaning (information) will be the same, but the syntax, grammar and words used will most likely be completely different (this is the data, rather than the actual information). compression algos like mpeg will keep the gist of the input, but discard everything else, to the point where the original data cannot possibly be recovered.

if you like, you could read the thread about "man stores multiple movies on 64kb", and you'll see why mpeg-2 et al are necessarily lossy - because otherwise you could hold the sum of human knowledge on a 3.5" floppy disk and still have space for the next thousand years or so worth of data.

[jggimi]

You can find step-by-step procedures here: http://www.doom9.org/conversionguides.htm

[Doobie]

Originally posted by AquaStealth
[B]Hello:)
I was thinking about all the possibilities of modern video technology
the other day and this question came to my mind:
Is it possible to use "reverse ripping" of a DVD to Xvid so that you
can decompress an Xvid-file and obtain a file of real DVD quality?

Dude, you do too much thinking about mundane things that you are unfamiliar with.

"Ripping" just means reading. A DVD-rip is something that was obtained by reading a DVD. And, an Xvid file is not really like a ZIP file. Most of the size decrease in a normal Xvid file (verses the ripped DVD file) comes not from compression but from throwing away data so there is no going back. DVDs use MPEG2 which is already lossy compression. Xvid is just more efficient lossy compression. You can convert Xvid to MPEG2, but with another loss of quality.

[Doom9]

You can convert Xvid to MPEG2, but with another loss of quality.Very true.. compare the results on your TV and you'll happily spare yourself all the pain of another conversion in the future.