Re: Compress a subset of bits form

"Ulf Reiman" <ulf.reiman@xxxxxxxxx> wrote in
news:1151910348.822701.58810@xxxxxxxxxxxxxxxxxxxxxxxxxxx:

Hi!
What is the best algorithm to compress the information, where a want to
point out a subset of 16 bits from 128 bits. a give one example where a
only use a subset of only 4 bits from the 128, we say we have a packet
of 128 bits, now a want to use the bit in place 6, 45, 68, 120, how
can a describe these places with a less bits as possibly? a do not want
to use 7 * 4 bits

/Ulf



I can see a long thread that may not get any where. But here is
a question for you. Is this information stand alone or what. Example
say you want to 2 bits from 5. Then what you may really want is
to express one of 5!/(2!3!) states that is one of 10 states.
Which would be an exceptable way to you:

Blank for one state
0 or 1 for next two states
00 to 11 for next four states
then your choice of any two 3 bit patterns for last 3 states.
This would gave you the least number of bits possible assuming
you want whole numbers of bits and is stand alone.

Next option would be let
000 to 101 be first six states
and 1100 and 1101 be next two states
and 1110 and 1111 by last two states.
This is best option for whole number embedded
as part of stream. Could easily be done
with huffman or arithmetic coding methods.

Third option if part of a stream use pure arithmetic
where you use roughly 3.22
bits of space in some stream of data In this one
alone can you use fractional bits since the state
of carry and high low registers contain the state
information needed to encode what ever other data
follows.

Any of the above could be done with a low precision arithmetic
quite well. And even here we are assumeing that its a
fixed number of bits from a fixed size. If this is varible
and can change you may have to store this fact with the method
you choose to use in the data itself.

Hope this helps with you homework!

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"

.

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