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  1. #1
    Star Lounger
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    WinZip - Music files

    My boyfriend has crashed is machine and needs to back it up so that he can re-install the Microsoft OS he's running. He has over 2000 music files he'd have to back up. Does anyone know the limitations (size limitations) of WinZip? Can he zip multiple music files in WinZip, compressing them, therefore having to burn fewer CDs?

    Thanks in advanced

  2. #2
    Uranium Lounger
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    Re: WinZip - Music files

    Sure, he could do that with Winzip - but it won't help much, because most audio formats are already highly compressed. It would be akin to putting an aluminum can in a can crusher twice just to be sure. Try it - zip up one file, MP3, WMA, whatever - using maximum compression - and then compare its size to the original.

    Bummer, eh?

    It's faster and more efficient to simply burn them onto a CD. The savings from zipping them probably wouldn't allow but maybe one additional song on a 650/700MB CD.
    -Mark

  3. #3
    Plutonium Lounger
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    Re: WinZip - Music files

    I agree with you in principle, but the method for checking is a bit suspect.

    Zip builds a dictionary of common things that it finds in the things about to be zipped, this dictionary is used to replace frequent sections with a shorter alternative. If you give it more files to work on then it is more likely to find things repeated that it can compress, so measuring how well it compresses 1 file does not necessarily tell you how well it would compress 1000.

    StuartR

  4. #4
    Plutonium Lounger
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    Re: WinZip - Music files

    Stuart,

    Are you sure about this?

    It's always been my understanding that compression in WinZip is on a file by file basis. Otherwise, deleting a file from a WinZip archive would be very complicated - the compression of all other files in the archive would have to be redone.

    In my experience, the compressed size of a file seems to be independent of the archive.

    Regards,
    Hans

  5. #5
    Plutonium Lounger
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    Re: WinZip - Music files

    Hans,

    Sure? Not really.

    This is something I have "always known". A google search for <font color=blue>Winzip Dictionary LZ, compression algorithm</font color=blue> turns up lots of interesting articles, but I didn't have time to do more than a quick scan.

    StuartR

  6. #6
    Plutonium Lounger
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    Re: WinZip - Music files

    Deleting a file from a Winzip archive isn't a problem. You leave the entire dictionary alone and just delete the one file. This could lead to a zip file that is a bit less efficient than if you generated a complete new dictionary, but it is still valid.

    StuartR

  7. #7
    Uranium Lounger
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    Re: WinZip - Music files

    It's worth noting that the compression algorith used to encode audio into the more popular formats is based on something different than that which WinZip owes its due. WinZip and other compression utilities like it are excellent for text, and other types of data where the information contained can be "collapsed."

    With audio encoding, the goal is to reproduce a sound for the benefit of a human listener. It is unnecessary to accurately recreate every characteristic of that sound's waveform (what the sound would look like if you could see it). MP3, for example, relies on determining which properties of the audio would be most important to the listener, and prioritizes the recording of these properties appropriately. The point of all that is to lend credence to the notion that effort outwieghs the usefulness of using ZIP to compress data that can't be easily reduced using the dictionary method.
    -Mark

  8. #8
    Plutonium Lounger
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    Re: WinZip - Music files

    Stuart,

    In the attached picture you can see that the compression rate for a file is the same whether that file is the only one in an archive or one of many files. So WinZip IMHO doesn't get more efficient when archiving many files.

    There is one factor - the file size of a WinZip archive is only slightly larger than the summed size of the compressed files. The overhead is small. If your HD has a large cluster size, this may make it efficient to store files in a WinZip archive even if compression rate is low. But this was more important in the past than it is nowadays, I think.
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  9. #9
    Plutonium Lounger
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    Re: WinZip - Music files

    Hans,

    A quick check shows that some files appear smaller, but not by much. I couldn't find any files that appeared bigger in the multi-file zip. I agree that this may not be significant, but the principle behind LZ compression should allow for greater efficiency. I think that Winzip has a fairly small fixed size dictionary, so there are probably significant trade offs here...

    StuartR
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