Data Compression
Criteria
Survey Formats
Basics
Compression Methods
Data Formats
Glossary
Index
A B C D
E F G H
I J K L
M N O P
Q R S T
U V W X
Y Z
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Glossary Data Compression
A
 ^ arithmetic coding
 The arithmetic coding offers the oppertunity to create a code that exactly represents the frequency of any character. A single character will be defined by belonging to a specific interval. For more frequent characters larger intervals will be used contrary to rare characters. The size of those intervals is porportional to the frequency. The arithmetic coding is the most efficient procedure but its usage will be restricted by patents.
Arithmetic Coding []
Subject: Arithmetic Coding []
B
C
D
E
 ^ Entropy
 In information theory entropy is a meassure for the information of a specific source.
Entropy []
F
G
H
 ^ Hartley
 At about 1930 Hartley had formulated the first mathematical fundamentals that was used later on to develope the information theory.
 ^ Huffman, David
 David Huffman had developed the Huffman coding at about 1952.
 ^ Huffman Coding
 The coding procedure developed by David Huffman generates a binary coding tree representing the frequency of each character. The code length derived from this tree is proportional to the frequency of the particular character.
Huffman Coding []
Subject: Huffman Coding []
I
 ^ Information Theory
 Information theory is concerned with coding and interchange of information. It was founded by Claude E. Shannon at about 1948. He had introduced information as a quantitative measure and the entropy of an information source.
Information Theory []
J
K
L
 ^ LZ77
 LZ77 is a data compression algorithm introduced by Jacob Ziv and Abraham Lempel in 1977. Basis of this procedure is the addressing of sequences that are already encoded. The previous contents is used as a dictionary for further encoding.
LempelZiv77 (LZ77) []
M
 ^ Message
 Basic parameter in the information theory.
Message []
N
O
P
Q
R
 ^ Run Length Encoding (RLE)
 Run Length Encoding schemes replace the repetition of characters by counters. RLE is a very simple mechanism that requires only limitted resources. It is in use e.g. for bitmap encoding or for processes with realtime conditions.
Run Length Encoding (RLE) []
Subject: Run Length Encoding (RLE) []
S
 ^ Shannon, Claude Elwood
 Shannon had founded substantial parts of the information theory and defined the Shannon Fano code together with Fano. He was appointed as a professor at the MIT.
 ^ ShannonFanoKodierung
 The coding procedure according to Shannon and Fano uses a binary code tree. The tree structure and therefore the code length represents the frequency of the coded characters. The Shannon Fano coding is not in common use because it is less effective than the Huffman coding.
ShannonFano Coding []
T
U
V
 ^ Variable Length Encoding
 The term variable length encoding describes procedures using codes with a differing length, e.g. Huffman codes. Those codes are in contrast to fixed length codes, e.g. ANSI text with 8 Bits per character.
Variable Length Codes []
W
X
Y
Z

