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Algorithms of BZIP2
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| Arsène Lupin 2007-11-07, 6:56 pm |
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Hi.
BZIP2 uses Burrows-Wheeler Transform to achieve better compression
rates than the ZIP (LZ77 variants). What's the transformation used on
the second stage? Move-to-front, Invertion Frequencies, Frequency
Count, etc.?
Thanks for the info.
Ars=E8ne
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| michael 2007-11-07, 9:56 pm |
| On Nov 7, 4:34 pm, Ars=E8ne Lupin <deten...@gmail.com> wrote:
> Hi.
>
> BZIP2 uses Burrows-Wheeler Transform to achieve better compression
> rates than the ZIP (LZ77 variants). What's the transformation used on
> the second stage? Move-to-front, Invertion Frequencies, Frequency
> Count, etc.?
>
> Thanks for the info.
>
> Ars=E8ne
BZIP2 uses MTF
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| Arsène Lupin 2007-11-08, 7:56 am |
| [color=darkred]
On that case why the BZIP2 results are better than "standard" MTF
ranks?
I downloaded a Mark Nelson BWT compressor, with an Arithmetic Coder
which performs MTF compression. The results are far from being even
close. And, in theory, the Arithmetic Coder should perform better than
the Huffman Codes.
Do you have any clue of why is that? What kind of transformation
before coding BZIP2 does, or it changes the source before the BWT?
Thanks, though, for the info.
Ars=E8ne
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| michael 2007-11-08, 7:56 am |
| On Nov 8, 6:31 am, Ars=E8ne Lupin <deten...@gmail.com> wrote:
>
> On that case why the BZIP2 results are better than "standard" MTF
> ranks?
>
> I downloaded a Mark Nelson BWT compressor, with an Arithmetic Coder
> which performs MTF compression. The results are far from being even
> close. And, in theory, the Arithmetic Coder should perform better than
> the Huffman Codes.
>
> Do you have any clue of why is that? What kind of transformation
> before coding BZIP2 does, or it changes the source before the BWT?
>
> Thanks, though, for the info.
>
> Ars=E8ne
see http://en.wikipedia.org/wiki/Bzip2
The steps bzip2 uses are described there.
- Michael Maniscalco
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| Arsène Lupin 2007-11-08, 9:56 pm |
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Thanks, Maniscalco, I REALLY got bad this time...
I even downloaded the source code, but I forgot to search the
wikipedia.
My bad. ~_~
Thanks for the info.
Ars=E8ne.
>
> seehttp://en.wikipedia.org/wiki/Bzip2
>
> The steps bzip2 uses are described there.
>
> - Michael Maniscalco
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