Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats


Huffman Code

Example

Characteristics

Variants

Static Distribution

Dynamic Distribution

Adaptive Distribution

Dynamic Huffman Code

Adaptive Huffman Code


Glossary

Index


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Static Distribution


Coding procedures with static Huffman codes operate with a predefined code tree. This is previously defined for any type of data and is independent from the particular contents. Normally such trees base on a standard analysis, e.g. for English texts, and take the frequency of each individual symbol to be found there.


Provided that the source data correspond to the adopted frequency distribution, an acceptable efficiency of the coding can be achieved. It is not necessary to store the Huffman tree or the frequencies within the encoded data. It is sufficient to keep them available within the encoder or decoder software. Additionally the coding tables do not need to be generated at run-time.


The primary problem of a static, predefined code tree arises, if the real probability distribution strongly differs from the assumptions. In this case the compression rate decreases drastically.


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Variants Variants Dynamic Distribution