Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats

Files

BZIP2

GZIP

Specification

Characteristics

Compression

Data Structure

Security Features

Platforms

Applications

ZIP

Audio Data

Image Data

Video Data


Glossary

Index


Download


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GZIP Compression Methods


The standard compression method is DEFLATE, a combination of LZ77 succeeded by entropy coding. Therefore a Huffman code is applied. Although the specification provides a corresponding header field, only the DEFLATE algorithm is specified for the time being.


The DEFLATE algorithm described in RFC 1951 is not restricted by patents as far as known. To ensure its free usage Jean-loup Gailly had investigated a large number of patents before starting developement. DEFLATE is also used for the ZIP format of PKWARE but the surrounding file structure and other compression methods of ZIP are incompatible.


DEFLATE []


Compression rates achievable with GZIP are comparable with ZIP varying due to different algorithms, parameter sets and applications used. The more complex BZIP2 and 7z algorithms also developed as open source projects provide a clearly better compression.


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External Links:

BinaryEssence is not responsible
for contents of external websites:

gzip.org []

7-Zip []

BZIP2 at gnuwin32.sourceforge.net []

GZIP GZIP General Characteristics Structure of GZIP Data