DVB – Digital Video Broadcasting

As you probably already know we will switch to digital television broadcasting (Europe is using DVB-T system, USA is using ATSC). But you probably don’t know what are the reasons and benefits of this transition. There are many important things you should be aware of. The most important is that you will still be able to use your old television set.

<Firstly, let’s take a look at the reasons for digital broadcasting. To get television sound and picture in our home we need a “way” to transfer the signals from TV station to us. One of the ways is terrestrial broadcasting. This means using transmitters on high transmitting sites to transmit signals that we can receive with rooftop or indoor antenna.

Terrestrial broadcasting uses radio waves. But broadcasting is just one of the services that uses radio waves. Therefore there is only a small amount of radio frequency spectrum allocated to television broadcasting. And this small amount of spectrum allocated to television broadcasting was used for many decades only for analog television broadcasting. In practice this means transmitting one TV channel at one particular frequency. In order to avoid harmful interference from other television transmitters operating on the same frequency there are very precise rules on the international level that regulate frequency usage.

A few years ago many countries have come to the situation where adding new TV channels to the terrestrial network was not possible because all frequencies (TV frequency channels) assigned to the these countries were already used. Therefore a new solution has to be found. And it was. Digital technology allows us to compress picture and sound and to generate various modulations suitable for data transportation. One of such technologies for digital data transmission is DVB-T. It means Digital Video Broadcasting – Terrestrial and is a substitute for analog television broadcasting. While analog television transmitter broadcasts only one TV program, digital television transmitter (DVB-T transmitter) transmits a package of various services (radio, television, teletext, subtitles, data, etc) called multiplex.

This new way of broadcasting brings us many new possibilities: better sound and picture quality, wide screen format (16:9 aspect ratio), high-definition television (HDTV) and more choice. Because digital broadcasting allows us to broadcast much more content than with widely used analog broadcasting, it is also much more spectrum efficient. This is one of the important motivations to switch to digital broadcasting. The most expensive resource is radio frequency spectrum which is limited and must be used in the most efficient way.

But ordinary people are not concerned with radio frequencies. They want TV channels and choice. DVB-T brings exactly this. Of course, the old TV set is not enough to receive new digital broadcasts. In general, you only need a set top box (STB), a box that you connect to the existing TV set. That’s it. With this box you will be able to receive all digital multiplexes and watch TV channels on your old television set as you did before. Prices for set top boxes in Europe vary, from about 20 Euro to few hundred Euros depending on options.

One the most important parameters when buying a set top box is for which country it was designed, i.e. which codecs or compression standards does it support. DVB-T is a widely used standard. Europe and many other countries are using it (USA, for example, uses a different system called ATSC). But this is not enough. There are many compression standards available, for audio and video.

There are two major compression standards for video, MPEG-2 and MPEG-4 (H.264). Most of the European countries are using MPEG-2, while also quite a lot of countries have decided to use an advanced compression standard officially known as H.264 (equivalent to MPEG-4 part 10 AVC). MPEG-4 is more future proof decision because it offers higher compression ratios compared to MPEG-2. The problem is that you have to have a set top box that supports it. If your country is using MPEG-2 then there is no need to buy MPEG-4 set top box. However, if you would like to receive channels from neighboring country that uses MPEG-4, than you need a set top box which supports MPEG-4. Almost all set top boxes that support MPEG-4 also support MPEG-2. And many countries that today use MPEG-2 are already discussing a switch to MPEG-4 compression. The MPEG-2/MPEG-4 labels are usually related to picture (video) compression. For sound there are also many compression standards. Countries that are using MPEG-2 for video usually use MPEG-1 layer II for sound. And countries which are using MPEG-4 for picture usually use AAC for audio. But be careful – all combinations are possible! This means that one broadcaster might use MPEG-4 for video and MPEG-1 layer II for audio.

Again, to switch to DVB-T broadcasting you don’t have to buy a new television set. Unless you would like to receive and watch HDTV – high definition television you only need a STB. In the case you want to watch HDTV you will need a wide screen TV set with higher resolution display (up to 1920 x 1080 pixels or image points). But be careful! HDTV TV set does not automatically receive and decode DVB-T signals. Those marked as “HDTV Ready” have ONLY the capability of DISPLAYING (not receiving off air or decoding) HDTV picture. Usually it comes from an external source: a HDTV DVB-T set top box, Blue ray player, satellite receiver, computer, etc. Of course, there are also integrated TV sets which have DVB-T receiver and MPEG-2/MPEG-4 decoders built in. Check before you buy.

Digital broadcasting is not something you should ignore. It is inevitable. Our future. Digital broadcasting brings us many new services and more choice. But it brings also a lot of problems and plenty of room for wrong decisions. Be extremely careful when buying a new television set or set top box. Check compatibility, compare prices, ask for demonstration, browse web and – enjoy!