The UK Home Automation Archive

Archive Home
Group Home
Search Archive


Advanced Search

The UKHA-ARCHIVE IS CEASING OPERATIONS 31 DEC 2024


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: Lossless Compression Help!



Title: Message
At a very simplistic level, compression algorithms often use:
Oh look - there are 10 spaces (for example) now.  I will replace them with
one space and a count of the number of spaces.
Getting more complex, the algorithms find recurring sequences of bytes - eg the word 'googleplex' appears 20 times in your file.  This is replaced with a (much smaller) token and somewhere in the file a copy of token=googleplex, so at decompression time, the token can be replaced with the original word.
Beyond that, I dunno - some algorithmic equivalent of David Blaine works it's magic and reduces the whole file to a single word :D
 
 
Tony
-----Original Message-----
From: Kenneth Watt [mailto:kennwatt@xxxxxxx]
Sent: 28 May 2002 13:02
To: ukha_d@xxxxxxxSubject: RE: [ukha_d] Lossless Compression Help!

Kinda, I honestly can't remember how it's done I read an article on the subject donks ago, IIRC, it takes out "blank" bits of info and replaces them with said blanks at the de-compression stage it's all very clever stuff I don't need to know about really but I think that's why you can get a text file that can be 70 odd % compressed and yet most images struggle to get beyond 10%.

 

Or I could be misguided ;-)

 

K.

 

-----Original Message-----
From: Ben McCormack [mailto:ben.mccormack@xxxxxxx]
Sent:
28 May 2002 12:55
To: ukha_d@xxxxxxxSubject: RE: [ukha_d] Lossless Compression Help!

 

but unzipping a zip file will replace that junk

-----Original Message-----
From: Kenneth Watt [mailto:kennwatt@xxxxxxx]
Sent:
28 May 2002 12:52
To: ukha_d@xxxxxxxSubject: RE: [ukha_d] Lossless Compression Help!

 

Just remember the next time you zip a file, your doing the impossible!

 

Not at all, a .ZIP file in most instances removes the junk from the file which is not really needed, look at the compression ratios for various files and you will see what I mean, some are more efficient than others at being zipped. Like a text file can be compressed far better than a JPEG or a BMP file.

 

K.


For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx


Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.


For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx


Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.




For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.


********************************************************************
Visit our Internet site at http://www.rbsmarkets.com

This e-mail is intended only for the addressee named above.
As this e-mail may contain confidential or privileged information,
if you are not the named addressee, you are not authorised to
retain, read, copy or disseminate this message or any part of it.
********************************************************************

Yahoo! Groups Sponsor
ADVERTISEMENT

For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Home | Main Index | Thread Index

Comments to the Webmaster are always welcomed, please use this contact form . Note that as this site is a mailing list archive, the Webmaster has no control over the contents of the messages. Comments about message content should be directed to the relevant mailing list.