Results 1 to 4 of 4

Thread: 7zip compression on ultra is ...

  1. #1
    Join Date
    Jul 2007
    Beans
    20

    7zip compression on ultra is ...

    I used a command to compress an ISO of mine

    Code:
    7z a -mx=9 ./my.iso.7z ./my.iso
    my.iso is ~2.4 GB (2614231040 bytes) large,
    using ratios (because the compression has not finished, ~55%) the 7zip archive should end at 2.3708 GB (2545709688.9 bytes).

    I've also compressed an .exe before, it was 234 mb, the compressed was 237,
    the question is, why does 7zip compress extremely well on some formats, but not at all on others?

    [edit]

    Also, should I tarball it first to see if that helps?
    Last edited by eulallia1; December 7th, 2008 at 09:24 PM. Reason: Tarball

  2. #2
    Join Date
    Sep 2006
    Location
    Silicon Valley, CA, USA
    Beans
    Hidden!
    Distro
    Ubuntu

    Re: 7zip compression on ultra is ...

    It is my understanding that certain data types are much more compressible than others. For example give a shot compressing WAV and MP3 files to illustrate the difference. Another good example would be BMP and JPG. Data that already exists in a compressed form will not yield too positive a result when re-compressing.

    Of course ratios are ultimately dependent on the compression algorithm...

    --Jeff Moorse

  3. #3
    Join Date
    Jul 2007
    Beans
    20

    Re: 7zip compression on ultra is ...

    Quote Originally Posted by jmoorse View Post
    It is my understanding that certain data types are much more compressible than others. For example give a shot compressing WAV and MP3 files to illustrate the difference. Another good example would be BMP and JPG. Data that already exists in a compressed form will not yield too positive a result when re-compressing.

    Of course ratios are ultimately dependent on the compression algorithm...

    --Jeff Moorse
    7z has multiple compression algorithms, excluding the compression level?

    ISOs aren't compressed by default (yet can be), I still can't figure out what's up with it.

    I'll try tarring it maybe?

    [edit]
    Also, compression ended and the archive is 2447256594 bytes (~2.3 GB).
    Last edited by eulallia1; December 7th, 2008 at 09:45 PM.

  4. #4
    Join Date
    Sep 2006
    Location
    Silicon Valley, CA, USA
    Beans
    Hidden!
    Distro
    Ubuntu

    Re: 7zip compression on ultra is ...

    I was thinking perhaps the data within the ISO: video files, mp3s, a ISO full of zip files (ok kidding on that last one)
    Cordially,
    Jeff Moorse

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •