Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats

Files

BZIP2

Compression

Data Structure

Data Integrity

Applications

GZIP

ZIP

Audio Data

Image Data

Video Data


Glossary

Index


Download


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BZIP2: Data Structure


BZIP2 data are always introduced by a header starting with the letters "BZ". Afterwards the identification of the block size immediately follows, being valid for the entire file ("h1 ", "h2", "h3" to "h9"). The parameter indicates the block size in units of 100,000 symbols each.


An internal file system is not specified, BZIP2 can only use the attributes of the local file system. Anyway only an individual file or a sequential concatenation of files may be encoded. From the file format neither file names nor time attributes can be reconstructed.


The actual original data are stored in blocks according to the selected size and will be protected individually with a CRC32 checksum. The error detection does not excede block boundaries and restarts with each new block.


Additionally a 48 bit identifier introduces each block. This block structure allows a partial reconstruction of damaged files, as described in the following.


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BZIP2 BZIP2: Compression BZIP2: Data Integrity