Best option to compress tomographical image data

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2013-12-23
2013-12-25
  • Andrey Kazak

    Andrey Kazak - 2013-12-23

    Greetings!

    I try to deflate quite a number of tomographical image datasets. A dataset is a folder of 20-30 GB full of TIFF images like this:
    http://www.datafilehost.com/d/725d0247

    Can you suggest the best compression algorithm from 7z cohort for such data please?

    Thank you!

     
  • Igor Pavlov

    Igor Pavlov - 2013-12-23

    1) If all TIF files are 16-bit images, you can use delta:2 filter for them:
    in GUI:
    f=delta:2
    in command line:
    -mf=delta:2

    If all BMP files are 8-bit images, you can use delta:1 filter for them:
    f=delta:1

    2) PPMD method can be slightly better than lzma or lzma2, but decompression will be much slower.

    3) If all files are different (there are no duplicates), you can switch off solid mode. So decompression of one file from set will be fast.

    Note also that if you compress 16-bit data with lossless method (like 7-Zip), compression ratio is not impressive. 16-bit data contain too much random data that can not be compressed.
    That is why compression ratio for 8-bit files is much better.

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-23

    3) Unfortunately most of files in my datasets are 16-bit images.
    2) PPMD increased compression ratio!
    1) For some reason
    D:\Temp\7z.exe a -mf=Delta:2 "D:\Temp\Raw.7z" "D:\Temp\Raw"
    results in
    System error:
    The parameter is incorrect.

    What could be the reason for this?

     
    Last edit: Andrey Kazak 2013-12-23
  • Igor Pavlov

    Igor Pavlov - 2013-12-23

    it must work in 7-Zip 9.30 or 9.32.
    -mf=delta:2
    -mf=delta:2 -m0=ppmd -mx

    and for old version 9.20:
    -m0=delta:2 -m1=lzma

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-23

    Is 9.30 or 9.32 stable?
    I use 9.20.

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-23

    I tested with version 7-zip 9.20 and WinRAR 4.11 and got the following rating (1 for the best):
    1) WinRAR with Best option
    2) 7-zip with -m0=delta2 -m1=lzma -mx=9 -ms=off -mtc=on
    3) 7-zip with -m0=PPMd -mx=9 -ms=off -mtc=on

    Thank you!
    Have you something to add?

     
    Last edit: Andrey Kazak 2013-12-23
  • Igor Pavlov

    Igor Pavlov - 2013-12-23

    -m0=delta:2 -m1=ppmd
    Can be slightly better for some files (not all).

    WinRAR 4.* supports special multimedia algorithm. So it's good for such 16-bit data.

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-23

    How can I use
    m0=delta:2 -m1=ppmd
    with version 9.20?

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-24

    Or these switches are for alpha-versions only?

     
  • Igor Pavlov

    Igor Pavlov - 2013-12-24

    -m0=delta:2 -m1=lzma
    works in 9.20 and later.

    -mf works only after 9.21

    But there is no difference. It's just simpler to write -mf in some cases.

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-24

    -m0=delta:2 -m1=lzma for 9.20
    results in the same compression ratio as
    -m0=delta:2 -m1=ppmd or -mf=delta:2 (9.30 or 9.32)

    Is this correct?

     
  • Igor Pavlov

    Igor Pavlov - 2013-12-24

    Default method is lzma2 in 9.30 and 9.32.
    But lzma2 and lzma provide same compression ratio for your data. So it's better to use lzma in your case.
    But you can use lzma2 with -mx3 or -mx1 switch, if you need
    fast compression with multithreading.

    -mf=something
    means
    -m0=something -m1=lzma2

    Just use
    -m0=delta:2 -m1=lzma
    or
    -m0=delta:2 -m1=ppmd
    and it will work in any version.

     
  • Andrey Kazak

    Andrey Kazak - 2013-12-25

    Thank you!

     

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