Data Compression


Criteria:

Specific Contents

Lossless Compression

Predefined Data Volume

Predefined Transfer Rate

Run-Time Decoding

Run-Time Encoding

Synchronous Coding

Data Integrity

Editing

Archiving

Survey Formats

Basics

Compression Methods

Data Formats


Glossary

Index


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Archiving


A variety of aspects has to be regarded if data shall be archived for long terms. The requirements resulting from this are far away from being trivial. Important aspects are:

Availabilty of the Decoder
Either the software, the corresponding operation system and a compatible hardware plattform necessary for decoding must be permanently available. A usable alternative is to establish a conversion process but this is only feasilbe by the help of an automated archiving system. For larger archives a manual conversion is economically not usefull. Additionally an automated updating requires data formats that do not produce compression artefacts during conversion.
Independant Data Format
With a growing period of time it will became more and more difficult to make a statement about the future use of the data. Therefore the format must be independant. Especially this is of importance for contents that is created for a special purpose, e.g. the publishing via internet. A future use will propably require a better resolution or a larger amount of colours.
Data Integrity
The propability for defects will increase with the archiving period or with the number of refreshs executed. The compression formats shall take this into consideration. All formats that result in total loss after a single defect must be avoided. Alternatively the whole data could be splitted into individual segments.
Optimization of the Archiving Resources
A high data compression rate could reduce the entire volume of the archive but causes a higher sensibility for defects too. The following aspects has to be reflected:
  • larger coding effort
  • lower storage capacity
  • lower efforts for copying
  • lower efforts for cyclic refresh
  • lower error redundance (additional redundance necessary)

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