Compression Techniques

In general these techniques can be divided into two main categories.

Lossless Compression :

If the compressed data is reconstructed and the original data is obtained without any loss of information then this technique is called lossless compression.

• The lossless compression is mostly used for general data such as text or programs.
• Some of lossless compression techniques:
• Huffman codes.
• Run length encoding.
• Lempel-ziv encoding.

Lossy Compression :

If the compressed data is reconstructed and the approximated original data and loss of data is occurred then this is called lossy compression.

• The lossy compression is used for images, videos or audio.
• Lossy compression techniques:
• JPEG : Used to compress pictures and graphics.
• MPEG : Used to compress video.
• MP3 : Used for audio compression.

Compression tools examples:

• Winzip, Pkzip, Compress, gZip.

Run length encoding :

It is probably the simplest method of compression. It is used to compress data made up of combination of symbols.

• The general idea is to replace consecutive repeating occurrences of symbols with one another.

Huffman Encoding :

In Huffman coding its assigns shorter codes to symbols that occurs more frequently and longer codes to symbols that occur less frequently.

  

Lempel-Ziv coding :

It is a dictionary based encoding. The idea is to create a dictionary of strings used during the communication session.

• In this there are two events. Building a indexed dictionary and compressing a string of symbols.

Examples for Lossless and Lossy compression :