Re: Compression test on permutations

On Apr 23, 4:56 pm, erpy <i...@xxxxxxxxxxxxxxxx> wrote:
Josiah Carlson ha scritto:

erpy wrote:
File description:

The file is made of 65536 bytes.
Each 256 bytes represent a pseudo-randomly ordered permutation of a
byte. (i.e. of all the numbers represented by 8-bits)
So, basically you have 256 permutations of size 256-bytes each, one
after the other.

Please see my replies to industrial_one in the jacko thread.
Generally, the "RAD" files that were being proposed were exactly this,
and you can generally reduce the size by around 25%-32% (assuming a
sufficiently precise arithmetic coder).

- Josiah

Apologies, the whole thread just disappeared from my server.
Would you please explain again how an arith coder would take off 25%-32%
of the chars ?

Best,
E.

Actually a trival change to arb255 would compress this type of file
the best.
You start with the full tree then remove a leaf for every symbol. If
you can''t
mod the code your self I could do it in a few days if needed.


David A. Scott
--
My Crypto code
http://bijective.dogma.net/crypto/scott19u.zip
http://www.jim.com/jamesd/Kong/scott19u.zip old version
My Compression code http://bijective.dogma.net/
**TO EMAIL ME drop the roman "five" **
Disclaimer:I am in no way responsible for any of the statements
made in the above text. For all I know I might be drugged.
As a famous person once said "any cryptograhic
system is only as strong as its weakest link"

.

Relevant Pages

  • Re: Compression test on permutations
    ... biject ha scritto: ... Would you please explain again how an arith coder would take off 25%-32% ... I bet you're far more accustomed with compressors source code...it would take me some time just to study the source. ...
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  • Re: Compression test on permutations
    ... Josiah Carlson ha scritto: ... Each 256 bytes represent a pseudo-randomly ordered permutation of a byte. ... Would you please explain again how an arith coder would take off 25%-32% of the chars? ...
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  • Re: Compression test on permutations
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