World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0003980578
Reproduction Date:

Title: Lzwl  
Author: World Heritage Encyclopedia
Language: English
Subject: Compression methods, Context tree weighting, Byte pair encoding, Elias delta coding, Warped linear predictive coding
Collection: Lossless Compression Algorithms
Publisher: World Heritage Encyclopedia


LZWL is a syllable-based variant of the character-based LZW compression algorithm[1][3] that can work with syllables obtained by all algorithms of decomposition into syllables. The algorithm can be used for words too.


Algorithm LZWL can work with syllables obtained by all algorithms of decomposition into syllables. This algorithm can be used for words too.

In the initialization step the dictionary is filled up with all characters from the alphabet. In each next step it is searched for the maximal string S, which is from the dictionary and matches the prefix of the still non-coded part of the input. The number of phrase S is sent to the output. A new phrase is added to the dictionary. This phrase is created by concatenation of string S and the character that follows S in file. The actual input position is moved forward by the length of S. Decoding has only one situation for solving. We can receive the number of phrase, which is not from the dictionary. In this case we can create that phrase by concatenation of the last added phrase with its first character.

The syllable-based version works over an alphabet of syllables. In the initialization step we add to the dictionary the empty syllable and small syllables from a database of frequent syllables. Finding string S and coding its number is similar to the character-based version, except that string S is a string of syllables. The number of phrase S is encoded to the output. The string S can be the empty syllable.

If S is the empty syllable, then we must get from the file one syllable called K and encode K by methods for coding new syllables. Syllable K is added to the dictionary. The position in the file is moved forward by the length of S. In the case when S is the empty syllable, the input position is moved forward by the length of K.

In adding a phrase to the dictionary there is a difference to the character-based version. The phrase from the next step will be called S1. If S and S1 are both non-empty syllables, then we add a new phrase to the dictionary. The new phrase is created by the concatenation of S1 with the first syllable of S. This solution has two advantages: The first is that strings are not created from syllables that appear only once. The second advantage is that we cannot receive in decoder number of phrase that is not from dictionary.


External links

  • Detailed description

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.