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What is Codec?

Updated on September 16, 2010

What is Codec? You type "define:codec" in Google search box, you will find a list of definitions of Codec on the Web. 

Codec is pronounced CO-deck, and short for 'compression-decompression', or short for 'coder-decoder'. Codec is made up by two words, similar to modem for modulator-demodulator. Codec may refer to a device inside the phone or at the cell system, or a computer program.

As a device inside the phone, Codec takes digitized voice and compresses it prior to transmission to the cell, and takes compressed voice received from the cell and decompresses it prior to playing it.

Raw media, for example, audio or video, file sizes are normally very large, a codec is a mathematical formula that analyzes the data in a file and determines how data can be removed while still maintaining an acceptable file quality. By removing data, the file becomes much smaller.

Most media players use DirectShow for playback. DirectShow, sometimes abbreviated as DS or DShow, is produced by Microsoft to perform various operations with media files or streams. DirectShow uses multiple DirectShow filters as building blocks to construct what is called a DirectShow graph.

Now we have Media files or streams, the audio and video renderers, and multiple filters between. A Media file is a root, the audio and video renderers are the leaves. During playback data flows from the root to the leaves. Each filter performs a subtask of the whole process. Typical filter are a source filter, also called a splitter, and decoders for the audio and video. A source filter is responsible for reading the file format and feeding the data to the other filters downstream. 

A DirectShow filter is not a codec.


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