Compression of random binary data

[Steven D'Aprano]

On Wed, 13 Jul 2016 12:29 am, jonas.thornvall at gmail.com wrote:

> Den tisdag 12 juli 2016 kl. 05:01:20 UTC+2 skrev Lawrence D’Oliveiro:
>> On Tuesday, July 12, 2016 at 5:52:27 AM UTC+12, jonas.t... at gmail.com
>> wrote:
>> 
>> > What kind of statistic law or mathematical conjecture  or is it even a
>> > physical law is violated by compression of random binary data?
>> 
>> Try compressing already-compressed data.
>> 
>> Does that answer your question?
> 
> Yes that is my question, and also a claim i can do it.

Can you also make a perpetual motion machine, square the circle, and find an
exact rational fraction equal to pi?


What gets me is the people who *say* that they can compress already
compressed data. We know they can't, because if they could, they could
compress it again and again and again and again until there was only a
single bit, AND STILL REVERSE IT, using no external storage. Your lookup
tables are part of the compressed data. If the "compressed file" plus the
lookup table is bigger than the original file, then you haven't really
compressed anything. You've just moved some of it from the file into a
lookup table.

So why do people claim that they can compress already compressed data? Who
are they fooling? Themselves?



-- 
Steve