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Theoretical question about UNcompressing

Discussion in 'DVD±R for advanced users' started by karen2003, Aug 11, 2004.

  1. karen2003

    karen2003 Regular member

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    Hi everyone. As my pile of backed-up DVDs is now in the 100s, and more than half of those were originally DVD-9's, it got me thinking ... would it be theoretically possible to come up with an "un-Shrink" program in the future that will "uncompress" all those compressed DVDs for re-burning on dual-layer media? Or is it more likely that when dual-layer media is as cheap as single-layer is now (anyone want to speculate as to when that will be? ha!), I will have to re-back-up all my DVD-9 originals?

    Again, this question is more theoretical than anything else. I guess the analogy I had in mind was the zipping and unzipping we can do with PKUNZIP or similar programs. Maybe that's a bad analogy -- I don't know enough about the technical aspects of this stuff.

    Most of my DVDs have been compressed using Shrink. How about some of you computer engineers out there working on an unShrink program for our future needs? :) Just a suggestion.

    Any thoughts?
     
  2. Nephilim

    Nephilim Moderator Staff Member

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    I would posit that "you can't make something out of nothing" would be appplicable here for the fact that you can't gain back quality that isn't there :)
     
  3. karen2003

    karen2003 Regular member

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    Ah, so the compression that Shrink does isn't like "zipping" a large data file to compress it? Guess that wasn't a good analogy. Can you explain the difference? I like to understand how these things work. Thanks!
     
  4. Veblin

    Veblin Active member

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    In simplest terms compressing with a transcoder discards the least important video data while keeping the most important video data. Transcoders try to determine what is most important to keep to retain quality.

    Any additional quality settings in a transcoder usually involve increasing the amount of time it takes to determine what is most important to keep. Of course any data that is discarded from the output is lost and can not be put back.
     
  5. baabaa

    baabaa Active member

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    Yes the term 'compression' is actually a little misleading BUT is exactly what happens.....

    (Simple terms)
    Repeated frames/empty spaces etc are removed (these areas take up bytes etc).....therefore the overall data is reduced - Hence Compressed.....

    Therefore as veblin stated when removed = lost forever.....

    Unless, you of course purchase the DL discs, and re-backup your originals - and in your case with >100, that would take some time especially as the DL media is only rated at 2.4x at the moment (30 mins to burn approx.)......

    However I feel the compression resolution reduction imposed by todays software packages (just movie backup)is minimal, therefore if you have any 2 episode film type scenario - then you would be able to insert them on one DL Dvd.........
    _X_X_X_X_X_[small]Beware of the Pixies - they move in over night and turn your life upside down

    [​IMG] [​IMG][/small]
     
    Last edited: Aug 11, 2004
  6. karen2003

    karen2003 Regular member

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    Thanks, guys. I didn't realize exactly what compression DID (i.e. remove frames). Now that I understand what it does, I see my original question was silly. :) In a few years when DL media is cheaper maybe I'll just back up the originals that had a lot of compression (which I can check with my trusty spreadsheet).

    Thanks again.
     
  7. ddlooping

    ddlooping Active member

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    Hi all. :)

    karen2003, transcoders (including DVD Shrink) do not actualy remove frames.
    Veblin's explanation is spot on. ;)

    I'd just like to add..
    ...and/or how to best spread the compression between frames of different type.


    _X_X_X_X_X_[small]~ ddlooping~ [​IMG]
    For DVD Shrink and related softwares guides and downloads, please visit http://www.dvdshrink.info[/small]
     
    Last edited: Aug 12, 2004

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