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Thread: paq8p2

  1. #1
    Programmer Jan Ondrus's Avatar
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    paq8p2

    paq8p2 is paq8p1 with some modifications in jpeg model
    - slightly simplified source
    - minor changes in compression ratio for jpeg.

    http://www.sendspace.com/file/t5yxdl

    using -5 setting:
    A10.jpg 842468
    A10.jpg.paq8p1 638756
    A10.jpg.paq8p2 637686
    DSCN3974.jpg 1114198
    DSCN3974.jpg.paq8p1 827269
    DSCN3974.jpg.paq8p2 827266
    football.jpg 115693
    football.jpg.paq8p1 70513
    football.jpg.paq8p2 70339

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    The Founder encode's Avatar
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  3. #3
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    A short test from me. I compiled paq8p1 and paq8p2 by myself and without asm support because I didn't manage to do it. I thought Visual Studio 2008 can compile them but it can only handle included nasm? It's a a 3648x2736 picture of two persons with a normal camera I guess

    Code:
    paq8p1 - 4378752 -> 3273336 - 127.84 sec
    paq8p2 - 4378752 -> 3269096 - 122.75 sec
    Reading the old paq8p thread it seems paq8p1 has some bugs or am I wrong? Before the version will be continue used, these bug(s) should be fixed.

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    Thumbs up

    Thanks Jan!

    Compiled...
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  5. #5
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    For completion I used the asm object file in Love Pimples package but compiled it with the same switches then before.
    It was really much faster. 97.11 sec. I didn't retest paq8p1 if someone is interested in this result I could do. But I think the same time can be subtracted.

  6. #6
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    Hi!
    My test scores (w/o timings, paq method -5):

    f.jpg = 112'038
    f.jpg.paq8p = 90'100
    f.jpg.paq8p1 = 90'100
    f.jpg.paq8p1_ = 90'100
    f.jpg.paq8p2 = 89'750
    f.jpg packed by stuffit 9.0.0.21 = 83'343
    f.jpg prepacked by precomp 0.3.8 (packJPG) = 87'608
    Good improvement, but still my testfile is still better compressed by precomp or stuffit - probably because it is progressive jpg.

    It's possible to add progressive jpg recognition to paq jpg algorithm?


    Second observation ? bmp and wav compression algorithms used in paq8p2 version aren?t looked like the best as it was used in older paq8pXX variations:
    Examples from my testbed:
    WAV:
    0.wav.paq8p = 1?342?234
    0.wav.paq8p1 = 1?342?580
    0.wav.paq8p1_ = 1?334?183 ? best wav algorithm from paq8p variations
    0.wav.paq8p2 = 1?342?234
    BMP:
    1.bmp.paq8p = 264?426 ? best bmp algorithm from paq8p variations
    1.bmp.paq8p1 = 266?187
    1.bmp.paq8p1_ = 266?187
    1.bmp.paq8p2 = 266?187

    Of course I understand that my testbed files couldn?t be objective for broader set of test files, but if it?s a regular situation, then maybe easy way to get small improvement in next versions is to use wav algorithm from paq8p1_ version and bmp algorithm from paq8p. It?s possible?

    Regards, Darek

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