Digital Video Broadcasting

Digital Video Broadcasting (DVB) is the most popular group of specifications to broadcast digital television, used all over the world through various transmission media. DVB has many standards, each suited for a specific transmission media. Each DVB standard is made in order to broadcast and receive in the most suitable and convenient way for that transmission media.

Here I will mention a few of the DVB standards and describe them briefly:-

Digital Video Broadcasting over Terrestrial networks (DVB-T)
DVB-T uses MPEG-2 or MPEG-4 (H.264) for broadcasting. This system is used worldwide for broadcasting free to air channels. It is mostly used by national broadcasters. Around the world, many countries have made it a law to upgrade national television to digital, the deadline being around 2009-2015. After the deadline, all analogue networks will be forced to shut down in these countries. The same also applies to radio networks, but those are not being discussed here.

In the U.K. (where I am now), the government has ordered the public and the broadcasts to "Switchover to Digital" by 2012. In 2012, all analogue networks will be shut down. Therefore the people are moving to services such as Freeview (also DVB-T) and Sky (pay television DVB-S) in order to avoid wasting money on a new television set or separate digital tuner.

Other countries too are making "switchovers" and moving to digital.

In Sri Lanka - Rupavahini Corporation announced a few years ago that they will go digital by 2008. But afterward, plans seemed to be cancelled and nothing seems to be upgraded. But behind the scenes, Dialog Telekom and another group called Sumathi have obtained licenses to broadcast digitally. Sumathi is already quietly broadcasting 4 channels, whilst Dialog is testing their systems with local channels. Dialog will soon launch a pay television service through DVB-T in Colombo and soon in other parts of the country, providing around 40 channels including 6 local channels (the ones already on Dialog Satellite TV). But no sign of national television broadcasters going digital themselves. Same applies for the radio broadcasters.

Digital Video Broadcasting over Multichannel Multipoint Distribution Service (DVB-MC)
All right, this system is basically Microwave broadcasting using MMDS. But in digital. This system uses the UHF frequencies, and broadcasts in MPEG-2 or MPEG-4. I've mentioned it here because of its presence in Sri Lanka.

In Sri Lanka - MMDS is used by the pay television operator Comet Cable in analogue form. But the service has been planning and promising to upgrade to DVB-MC for ages now. The latest promise is to upgrade by September 2007. But nobody can really be sure this will happen, as many false promises have been given before. But we should wait and see what happens.

Digital Video Broadcasting over Satellite networks (DVB-S and DVB-S2)
This technology is used for satellite television worldwide. It can be used with MPEG-2 or MPEG-4 encoding (nothing new). The newer version of the standard, DVB-S2, provides more features and facilities to save bandwidth and give more interactivity.

In Sri Lanka - Dialog Satellite Television, TV Lanka and Srilakvahini. These are the main companies which broadcast using DVB-S in Sri Lanka. Dialog TV is possibly planning to upgrade to DVB-S2 soon (not sure though).

Digital Video Broadcasting over Cable networks (DVB-C)
This standard allows for unlimited broadcasting of channel over a cable network. There is simply no limit to the number of channels broadcasted, and the total bandwidth is only the maximum of the cable used. That means the total bandwidth can fit almost two HDTV channels simultaneously on a coxial cable. Imagine the bandwidth and possibilities with a fibre optic network!

The high bandwidth allows for the best picture quality and sound quality possible. And there is little cost in operating a cable network, resulting in a very low price of pay television on cable networks.

In Sri Lanka - The cable television network Lanka Broadband Networks (LBN) uses DVB-C in its digital network. LBN is speedily expanding their channel collection and their only limit is coverage. They are the best pay television network in Sri Lanka because of this.

Digital Video Broadcasting for Handheld devices (DVB-H)
This standard uses almost the same technology as in DVB-T. However, the DVB-H television is suited to be used on battery powered devices with limited processing power and small screens. DVB-H allows for devices such as mobile phones to view television without wasting battery power.

Many countries have already deployed DVB-H networks, and many mobile phones already support the system (including some phones in the Nokia N Series).

In Sri Lanka - Dialog is planning to launch a DVB-H network soon.