CODEC DEVICES

You must have played mp3 songs or seen movies on your computer using applications like Winamp, Windows Media Player, Real Player, Xing Player, etc. These applications use ‘compressor-decompressor’ software programs, commonly called CODEC. These programs are used to code and decode data or signals from one format to another so that the end devices are able to interpret and play the signals. Media like audiotapes and VHS/Betamax tapes use analog signals to store the files while CODECs are meant to store digital files.

How CODEC works:

CODEC devices, in addition to the appropriate software, also have analog-to-digital and digital-to-analog converters used for audio and video data. They use digital signal processing, filtering, impedance synthesis, filters, etc. to code/encode the data. In video signals, the audio, video and metadata streams are combined or joined together using a video file format. Common video file formats are: mpeg, .mov, .mp3, etc.

Selection:

The basic criteria are:

• Audio CODEC: Used to compresses/decompresses digital audio signals or data with reference to standard audio file format or streaming audio format. Some audio formats are mp3, DTS, WMA, etc.


• Video CODEC: Used to compress digital video. Common formats are: MPEG (part 1, 2, 3, 4), Windows Media Video, Real Video, DivX, etc.


• Loss compression: Some loss in data quality occurs in this type of compression. Common types are mp3, WMV, DTS, etc. Movies use this kind of compression.


• Lossless compression: The original signal quality is retained. This produces higher file sizes. These are used in digital signal processing applications where further data processing will be done.


• Channels: Channels are individual lines of data that make up the signal. The higher the number of channels that the device can accommodate, the better the quality will be (e.g. 4/8/16/ 32 channels).


• Other factors are the type of chip, voltage, etc.

Applications:

CODEC allow you to enjoy digital movies and music. They are also used in VoX systems for filtering and pulse code modulation, analog line termination, encoding of POTS subscriber lines, integrated access devices, SOHO/residential gateways etc.