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Thread: impresseed by RPE preprocessor

  1. #1
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    I just stumbled upon REP a compression preprocessor.

    and did this little test which impressed my a lot.

    Dreamfall.mdf - 4.00GB
    Dreamfall.mdf.rep - 3.66GB
    Dreamfall.7z (ultra 3.68

    After decompression i did a CRC32 verify and the files was the same.

    why i was impressed is beacuse it did it very faster then 7-zip

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    Member Surfer's Avatar
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    At some files REP is more efficient (got ~0,4 MB from Archlinux-i686-2007.08-2.ftp.iso - which is little over 30MB - using REP + RAR, ECM + RAR was a bit weaker). Anyway, what is the size limit for ECM? I know I wanted to try it on some DVD image and was shown an error.

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    ECM only works on CD's and it dons't handle big files (above 2gb?)

    What does REP do since it so fast and better on some big files ?

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    Programmer Bulat Ziganshin's Avatar
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    Quote Originally Posted by SvenBent
    What does REP do since it so fast and better on some big files ?
    its algorithm is briefly described in cpp file, together with further references to RZIP paper

    shortly said, its just lz77 alorithm which replaces strings with references to previous occurences of the same strings. its specifc is that repetitions are found on very large distances. so, the best way should be to use ecm+rep+lzma, as FreeArc itself does in -max mode

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    #Bulat Ziganshin

    so its a kinda like LZ77 algo with a big dictionary size?

    i tried further compression with 7-zip ultra. but i gave me a bigger filezie.

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    Programmer Bulat Ziganshin's Avatar
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    Quote Originally Posted by SvenBent
    so its a kinda like LZ77 algo with a big dictionary size?
    yes, its LZ77 compressor with big dictionary

    Quote Originally Posted by SvenBent
    i tried further compression with 7-zip ultra. but i gave me a bigger filezie.
    this depends on the type of data. f.e. in SqChart2007 test, compression of CD image was improved by ~7% (you may compare results of 7-zip and FreeArc 0.40)

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