Re: I know this won't work, I just want to know -why-.

Claudio wrote:
) I would be glad to replace believing with knowledge, so I have put here
) an example of my reasoning behind 'this strange worldview':
)
) #01: Let's archive a 100 bit long string along with 10 bits of error
) correction data. This makes a 110 bits large archive file i.e. 10%
) additional data for error correction.
) #02: Let's assume, that only maximum of 5 bits in the 100 bit long
) string can get damaged (and none in the correction data area). This
) makes maximum of 5% of damaged data.
) #03: With the 10% additional error correction data available, the error
) correction algorithm should be always able to recover the original data
) where maximal 5% of it is damaged , so:

Well let's see.. I googled for it:
http://www-math.mit.edu/~djk/18.310/shannon_bound.html

According to the formula given, to transmit over a channel that has 5%
errors, you need 28% recovery data. That would be roughly the same as
what you calculated.

) ...
)
) Is this wrong or right and if wrong which statement is wrong in the
) reasoning chain above?

It seems right, except for wanting to be able to correct 5% of errors with
only 10% of ECC data. Those figures probably come if

)>> For example, audio CDs and CDROMs contain error correcting codes.
) As I have read somewhere it can't be neglected, that CDROMs provide
) silently wrong data, so the chance to get an error here is not so tiny,
) that it can be skipped from practical consideration.

On a CDROM, 2048 bytes of data are ECC-encoded onto 2352 bytes.
That's almost 15% of ECC data, and I guesstimate that means you can
recover from 2% or 3% of flipped bits. Now, on CDs there are another
two levels of ECC, the same as on audio CDs. These levels add 8 bytes
of parity info to 24 bytes of data. So, 2048 bytes of data eventually
become 3136 bytes on the CDROM. That's over 50% of recovery data.



SaSW, Willem
--
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 or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT
.