Best compression from command line

Lior T
  • Lior T

    Lior T - 2010-11-23


    I am trying to achieve the same compression ratio from command line that i achieve when using the GUI  (7z, LZMA, Ultra-Compression - using default values in 7zip version 9.17 beta).

    i tried several variation, one of which is:
    7z a -t7z -mx9 -ms=30f10m -mhc=on -r  c:\temp\line.7z "d:\xxx\yyyy\*.*"

    The resulting output is a staggering 18% less compression than what i get using the GUI.
    Can anyone please explain to me what i did wrong in the parameters? (i also tried ms=on although this is less fitting my needs).


  • Igor Pavlov

    Igor Pavlov - 2010-11-23

    Just don't use complex commands. Use simple things:
    7z a -mx c:\temp\line.7z d:\xxx\yyyy\*

  • Lior T

    Lior T - 2010-11-24

    Hi Igor,

    I tried what you wrote just now and it yielded the same results - the GUI produced an 118,007KB file while the command line produced a 124,554KB file (i am compressing several hundreds of files in and including subdirectories).

    I also tried upgrading to v9.20 but that gave the same results.

    any idea?

  • Igor Pavlov

    Igor Pavlov - 2010-11-24

    7z l cmdline.7z -slt > cmdline.txt
    7z l gui.7z -slt > gui.txt

    And compare them.
    Look for example dictionary size after "LZMA:" in "Method".

  • Lior T

    Lior T - 2010-11-24

    Hi Igor,

    Sorry, it seems that a couple of files stayed in the .7z file from a first trial, and since i always updated the same 7z file, they stayed there and padded the total file size with about 10MB . Once i printed the content like you asked, i immediately saw them and removed them from the 7z.

    It now works the other way around and the command line produces a 2MB smaller file :)

    thanks for the help,
    and thanks for the app!



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