Codec: Difference between revisions
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# '''codec''' stands for '''compression/decompression'''. A codec is a kind of algorithm or a computer program that reduces the size of a file. | # '''codec''' stands for '''compression/decompression'''. A codec is a kind of algorithm or a computer program that reduces the size of a file. | ||
# The term codec is used to design chips that perform data conversion | # 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). | 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 | 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 == | == Technology == | ||
| Line 18: | Line 17: | ||
; Lossyness | ; Lossyness | ||
* Lossy compression means that you loose data (e.g. as in MPEG or JPEG). | * 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. | Here is an example. The number ''8.9996666'' could be compressed as | ||
8.9[ | 8.9[3]6[4] -or- 8.9 | ||
The second alternative is lossy, but may be good enough for your needs ... | The second alternative is lossy, but may be good enough for your needs ... | ||
== Compressions formats == | == Compressions formats == | ||
This inventory is absolutly not complete, see the [http://en.wikipedia.org/wiki/Data_compression Wikipedia] article | |||
=== Lossless === | === Lossless === | ||
Revision as of 17:39, 19 March 2007
Definition
- codec stands for compression/decompression. A codec is a kind of algorithm or a computer program that reduces the size of a file.
- 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
- 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
- JPEG
- Digital images, a sequence of several algorithms
- MPEG
- A family that includes MP3 and AAC, also a sequence of several algorithms