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Zip Zip

Discussion in 'Computer Talk' started by MarineCorps, Nov 20, 2003.

  1. MarineCorps

    MarineCorps Explosion!

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    Just wondering can I zip a zip file to constantly decrease the size of the origanal file?
     
  2. Turner

    Turner Deity Retired Moderator

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    You mean zip the file, and then zip the zip file, then zip the zipped zip file? No, I don't think so. But then, I've never tried it.
     
  3. Speedo

    Speedo Esse Quam Videri

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    Rezipping once may save some space but its not really worth the trouble. (my test file went from 2.36mb to 2.31mb) Zipping more than that doesn't have any affect.
     
  4. Aphex_Twin

    Aphex_Twin Evergreen

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    If you really want to compress, use Ace.
     
  5. Grisu

    Grisu Draghetto Retired Moderator

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    no, there's only so many redundant data that can be left out. zipping a second time might decrease the size slightly but that's it.
     
  6. Jeratain

    Jeratain On the can.

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    Get WinRAR. Better compression than Zip and Ace.
     
  7. Moonsinger

    Moonsinger Settler Retired Moderator

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    The answer is "no" and I'm 100% sure of that. In some case, the second time you zip it, the file size may be a little bit smaller and may be a little bit bigger too.
     
  8. ainwood

    ainwood Consultant. Administrator

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    Wot Moonsinger said. When you recompress a zip file, the only reduction in size you are likely to get is the compression of the file header (ie not the compressed data). However, the file then needs to add another header, and another dictionary on the end etc etc.
     
  9. Zwelgje

    Zwelgje Deity

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    I once had a zip file which was zipped and then made into a rar (or an ace, can't remember) file. The compression obtained by that was huge! :eek:
     
  10. Comraddict

    Comraddict C.IV

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    depends what you are compressing at first place. images ,mp3 etc are already compressed and you can't compress them any more. try if you don't believe me
    on other hand, doc files, exec. files and similar stuff offers good compression rate.
     
  11. MarineCorps

    MarineCorps Explosion!

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    Hehe try an entire civ 3 mod. I have a 56k modem at home while at school I can download the mod faster then 24 hours :eek: more like 3 minutes at school. But I did try rezipping it and indeed it only made it bigger, but I don't have winrar at the computer I'm going to work on tommorow so I will have to download it to the computer. But I do have it at home so I will be able to extract it.
     
  12. damunzy

    damunzy recovering former mod Retired Moderator

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    I have seen that also.

    And the files get LARGER if you try to zip them twice as there is nothing more to compress plus you add the extra overhead - again. The difference between zipping twice and zipping and then RARing is that they use different compression methods if I remember correctly.
     
  13. GenghisK

    GenghisK ...

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    Actually, as you could know, compressing a file, encoding a video/wav/image, is equivalent to maximizing the file's entropy. Which is understandable. If there are redundant (=same) strings in a file, you can still compress, and add to your compress dictonnary. Actually a zipped file would have an entropy close to one (generally 9x.xx% and not 1, of course, it's impossible to reach 1). Now, if you try to zip a zipped file, or rar an aced zipped file, you will only and likely get it bigger, since you have to create a dictionnary, that will add to the filesize.

    Anyway, check out www.7-zip.org. It's free, it's NOT compatible with the genuine zip format, but it's told to be much more efficient than zip, even better than rar/ace themselves. Drawback? Of course, time. It takes a loooooooong while to compress. Actually a test on 650meg of music files lead to:
    => ~625meg RAR
    => ~600meg 7zip

    But 10mins compress for RAR, 23mins for 7zip. Now you see whether space is worth time ;)
     

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