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Elegant Compression in Text (The LZ 77 Method)

submitted by Aard Vark

(oritteropo)
1 decade 5 months 2 weeks ago

YouTube Description:

Text compression methods such as LZ can reduce file sizes by up to 80%. Professor Brailsford explains the nuts and bolts of how it is done.

Original Compression film: http://youtu.be/Lto-ajuqW3w
EXTRA BITS - Text Compression meets probabilities: http://youtu.be/cCDCfoHTsaU
Cross Site Scripting with Tom Scott: http://youtu.be/L5l9lSnNMxg

http://www.facebook.com/computerphile
https://twitter.com/computer_phile

This video was filmed and edited by Sean Riley.

Computer Science at the University of Nottingham: http://bit.ly/nottscomputer

Computerphile is a sister project to Brady Haran's Numberphile. See the full list of Brady's video projects at: http://bit.ly/bradychannels

10 Comments

Moving this video to oritteropo's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.

Very interesting. Shall promote when I have a point.

*promote

Promoting this video and sending it back into the queue for one more try; last queued - promote requested by Deano.

To further illustrate the complexity involved in compression, think about the following:
If I replace "The computerphile channel handles computer topics" with "The computerphile channel handles <30,8> topics", how does the decoder tell the difference between the 2 byte <30,8> pointer and the data it represents?

ant

*geek

Adding video to channels (Geek) - requested by ant.

compression is fascinating. i used to work for a mobile phone OS company where i modified the language variant compiler to compress files based on a premade dictionary of words which were common over the whole software - it cut down the ROM size by many megabytes (which was a big deal back then). You could cut the amount of traffic on the internet by having a dictonary of common cats stored in the image decoder.

teebeenz says...

Huffman is my fav example, with PPM my second. PPM being the king these days.

Somewhat related to PPM, I also quite liked Ian Phillipps' entry in the 1988 IOCCC:

http://www.ioccc.org/years.html#1988_phillipps

Huffman is my fav example, with PPM my second. PPM being the king these days.

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