What are various compression techniques?

Answer:- Compression:- Compression refers to the reduction of the size. Reduction of the size helps in the transmission of the data in network.
Following are various techniques for compression of the data:-
a)     Lossless Compression: Lossless compression is the set of compression techniques in which data is compressed in such a way such that no information is lost at the time of decompression. Following are three general techniques under lossless compression.

Character count:- In this method, If same character is being repeated multiple time, instead of repeating the same character special symbol is inserted followed by frequency of continuous repetition. It is assumed that special character consumes less space in comparison to normal characters.

e.g.    333333355555577777AAAAAA3222222
will be compressed as:-  #37#56#75#A63#26

Relative Compression:-  In this method repeated words or repeated statements(preferably longer) are stored at one memory address. When same word of statement is repeated than instead of writing the word the memory address in referenced. This approach may also compress the data up to the great extent.

LZW Compression techniques:-  In this approaches the coding style is selected based on the frequency of the characters. e.g. if A is coming in the text again and again will be given small code, If Z is coming rarely may be given longer code.

b)     Lossy Compression:-  This is special kind of compression technique used for video and image compression. In this method ignorable information (e.g. corner pixels in video) are lost at the time of compression. Therefore at the time of de-compression exact size is not obtained as it was before compression.
This method drastically can reduce the size, but obviously we need to compromise with some unrelavent information.
In this method graphical objects are re-drawn as 3D-vectors and these vectors are transmitted.


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