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.

High Definition Television Using Led and Laser Beams

High definition televisions are in a great demand these days. The new technologies have diverted the focus of viewers from Black and White to Color picture that has far better resolution and picture quality.

Today, these high definition televisions have gone into more sophisticated system. So, the manufacturers have given more attention to the appearance of the picture on the screen using various color schemes. Consequently, the vast change made into this field is the replacement of tubes or bulbs that give off white light that filtered into primary colors and remixed with Lasers and Light Emitting Diodes or LEDs.

The idea to replace these lamps with LEDs or Lasers is to get much better color saturation with an efficient design.

These optical components do not beam white light, but rather its basic three building blocks: red, green and blue. Beams are emitted in narrow beam of wavelengths near to those of single, pure colors, giving off the brilliant, saturated red of a blazing sunset or the glittering, luminous blue of a rainbow. Beam these three primary colors in various intensities at one spot on the television screen, and a palette of hues can be created in a wider range than in TVs without this technology.

The utilization of such components have added to an advantage besides excellent resolution, reduced flickering problem, and improved brightness and color contrast that the LEDs are expected to last the lifetime of TVs than the previous bulbs which require replacement in every few years. Moreover, the cost in manufacturing is also decreased since LEDs are highly inexpensive as compared to the bulbs or tubes.

Author: Gary Jones (Component Engr.)
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