Codec

Draft

Definition

1. codec stands for compression/decompression. A codec is a kind of algorithm or a computer program that reduces the size of a file.
2. The term codec is used to design chips that perform data conversion

Compression is used by most multimedia formats like video streaming, digital images (e.g. JPEG and PNG) and music (e.g. MP3). It is also popular for software distribution and archivation, e.g. zip/jar archive files contain compressed files. Gzip of bzip2 is used to compress *.tar archives.

Technology

Usually there is a choice of two kinds of features

• loss-less vs. lossy
• High compression ratio vs. high speed compression/decompression

Lossyness

• Lossy compression means that you loose data (e.g. as in MPEG or JPEG).
• Such algorithm take into account human perception, i.e. the algorithms for sound, image and video compression are not the same.

Here is an example. The number 8.9996666 could be compressed as

8.9[3]6[4] -or- 8.9

The second alternative is lossy, but may be good enough for your needs ...

Compressions formats

This inventory is absolutly not complete, see the Wikipedia article

Lossless

(usually for data including vector graphics and software)

LZW

• Used in GIFs and Unix compress

Deflate (a combination of LZ77 and Huffman coding)

• ZIP, gzip and PNG

Bzip2

• Very high compression rate

Lossy

(usually for non-vectorial multimedia)

JPEG

• Digital images, a sequence of several algorithms

MPEG

• A family that includes MP3 and AAC, also a sequence of several algorithms

Links

• http://en.wikipedia.org/wiki/Data_compression