With the immense growth of technology, watching TV has become more sophisticated. Early days we watched TV with the help of an analog antenna and the TV. It is the traditional TV system that we are accustomed to. At present, with the introduction of IPTV, watching TV has become more user-oriented. IPTV is the most interesting technology that has revolutionized the world of television; because it has given users wide range of options in watching. Users can have more interactions with the TV system as they are given the chance to control the program at their will; rewind, pause, add to playlists, watch previous programs during a convenient time and so on.

In Sri Lanka you are able enjoy the IPTV facility. According to my knowledge it has been in the local market since 2008; so at present you might be using IPTV at home. I thought it will be good to write an article on IPTV systems to enhance your knowledge on it.

IPTV stands for Internet Protocol based TeleVision. It is the mechanism which transports television content over the Internet. In a nutshell, video/audio streams are encoded and transmitted as IP packets over the internet and the receivers decode them to show them to the users. But let me explain you how the IPTV systems work.

I referred "http://www.althosbooks.com/ipteba1.html" to compile this information as I thought that reference is pretty good to understand the basics.

IPTV system gathers data from various sources like live broadcasts, stored media on the internet, and other types of communication links and so on. A centralized place called Headend, manages all data received and prepares in a way that they can be transmitted. That means data management and encoding/modulating are done in this place. Managed and modulated data are transmitted over broadband connections. Signals are transmitted as IP (Internet Protocol) packets.

Received signals are processed and converted into a format that allows users to watch TV, by a special equipment places at each user's home, Set-Top-Box (STB). If you use IPTV at home, it is the box that you switch ON before you watch TV. The following diagram explains the functionalities in a nut-shell:

Ref: http://www.althosbooks.com/ipteba1.html

The IP STB extracts the transport stream (TS) from IP packets. The channel decoder detects errors in the signal and corrects them and sends the transport stream to the descrambler assembly. The descrambler assembly gets key information from either a smart card or from an external conditional access system (e.g. via a return channel). Using the key(s), the STB decodes the transport stream and the program selector extracts the specific program stream that has been selected by the user. The DEMUX circuitry of IP STB then demultiplexes the transport stream to obtain the program information.

Demultiplexing is the mechanism of extracting each single signal from a multi-signal transport medium. It is the opposite of multiplexing. Multiplexing is arranging many signals in one transport medium to ease the transmission.

The program table provides information to select streams are for video, audio and other media for that program. The program stream is then divided into its elementary streams (voice, audio and control) which is provided to a compositor that create the video signal that the TV can display. Refer the diagram below.

Ref: http://www.althosbooks.com/ipteba1.html

You might be wondering how video can be sent via an IP transmission medium. The following diagram illustrates that an IP video system digitizes and reformats the original video, encodes and/or compresses the data, adds IP address information (unique identifier in the internet) to each packet, transfers the packets through a packet data network, recombines the packets and extracts the digitized video, decodes the data and converts the digital video back into its original video form.

Ref: http://www.althosbooks.com/ipteba1.html