Can I compress mp4 files to zip?

Discussion in 'macOS' started by bsheridan, Aug 2, 2008.

  1. bsheridan macrumors 6502

    bsheridan

    Joined:
    Jan 11, 2008
    #1
    If I compress mp4 files to zip they reduce to about a third in size. does that mean if i unzip that zip file I will have then lost data from the original mp4 file?
     
  2. munson macrumors 6502

    munson

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    #2
    No, it will decompress into the original file. If done too many times, however, you can lose a very small amount of quality from the mp4 file. Too many time referring to compressing the decompressed file.

    File 1 > compress to zip > decompress that file, receive file two > compress file 2 -- That will redice the quality by a very minscule amount each time you do it, which can add up. It's similar to converting audio files.
     
  3. FSUSem1noles macrumors 68000

    FSUSem1noles

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    #3
    The ZIP file format is a lossless data compression and archival format so you shouldn't experience any data loss at all..
     
  4. munson macrumors 6502

    munson

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    #4
    Right, ZIP files are considered lossless, but nothing is perfect. ;) It shouldn't be any problem at all, unless you for some reason or another, want to keep compressing over and over again. I mean, I GUESS you could be that bored...
     
  5. bsheridan thread starter macrumors 6502

    bsheridan

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    Jan 11, 2008
    #5
    thanks for the replies. I don't plan on continually compressing/decompressing the file, just compress the mp4s burn to dvd for backup (i like having a hard copy)

    On a side note, could you explain in simple terms how it is lossless? I always figured a bigger file meant more data???

    thanks.
     
  6. FSUSem1noles macrumors 68000

    FSUSem1noles

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    #6
    In simple terms as possible, lossless compression (ZIP) is a group of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. And as the poster above stated it's not "perfect" but it's close enough..

    And yes, if you keep compressing it over time you more than likely will experience a loss/decrease in quality..
     
  7. munson macrumors 6502

    munson

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    #7
    What it means is that when you compress into a ZIP (lossless, as we mentioned), you will not lose anything of the original file. The mp4 file is structured/built in a way that reads it as a media file, whereas a ZIP file takes all that data, and crams it into one small space that is less "open"

    You can think of this as something that folds up, like a chair. The only way it is useful is when it's "open" but even when it is closed all of the "data" is still there.
     
  8. FSUSem1noles macrumors 68000

    FSUSem1noles

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    #8
    Great analogy!
     
  9. bsheridan thread starter macrumors 6502

    bsheridan

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    Jan 11, 2008
    #9

    I can grasp the idea better now, thanks :)
     
  10. portent macrumors 6502a

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    Feb 17, 2004
    #10
    No, you won't. Ever. Unless something goes wrong (your hard disk crashes, your computer locks up, your electricity goes out right in the middle of things) you will experience no decrease in "quality." Zero. Zip. The bytes you get out are exactly the same as the bytes you get in. That's the whole point of lossless compression. You could go back and forth constantly for a hundred years, and you'll get exactly the same thing out as you put in.

    You can't have a decrease in "quality" when you have exactly the same file. Bytes don't get worn out, dirty, rusty, or dull.
     

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