We all know that there are invisible, magical, ‘sciency’ signals being broadcasted through the air 24/7 that allow us to pick up things like television, radio and even cellphone calls… But what exactly are these signals and how do they work? What is all this talk about digital television and how will it affect our daily lives? I have attempted to answer all of these huge yet relevant questions and provide you with all the important information you should know as we join the international migration to digital TV.
Back to basics: How does an analogue TV transmission work?
At current, we receive our TV broadcasts through analogue signals. Analogue signals comprise of a video signal and a separate sound signal that when combined, produce the channels we watch on our televisions.
At the very beginning of the whole broadcasting process is a camera. The camera captures multiple pictures of a scene and combines them in frames producing what we know to be a video recording. These multiple frames are then ‘rasterized’ by the camera- they are converted into coded rows of dots called pixels of specific colour and intensity. These rows of pixels are combined with horizontal and vertical synchronisation signals that instruct our television sets to display the pixels in a particular sequence.
Together, the synchronisation signals and the rasterized frames make up the composite video signal that is broadcasted along with its accompanying sound signal. We broadcast them through radio waves (a type of electromagnetic wave that carries information) which we are able to pick up with an aerial.
What is Digital TV?
Digital signals are broadcasted by digital satellite systems or digital cable systems (what Americans refer to as “cable”). These systems make use of technology like MPEG4 compression which makes digital signals occupy up to nine times less bandwidth than analogue signals. In South Africa, the digital signals will be broadcasted from existing terrestrial broadcasting infrastructure in order to reduce costs. The signals will then be picked up by a receiver called a Set Top Box. The Set Top Box converts the digital signal to an analogue signal which can then be interpreted and displayed by your regular TV. Digital TV is much preferred over analogue transmissions because of its major advantages:
- HD TV: High Definition TV or HD TV makes use of the extra bandwidth by transferring larger video and sound signals that result in a better sound and image quality on an HD ready television. *Most TV’s sold after 2009 in South Africa are specified as being HD ready.
- More channels: The extra bandwidth means more channels can be broadcasted at once and you can pick up all of the existing free-to-air channels as well as various new channels which are ready to be broadcasted exclusively on the digital platform. *Current DSTV subscribers will not be able to pick up these new channels without a Set Top Box
- The Set Top Box: Set Top Boxes will be able to connect to cellphones, the internet and even USB modems providing greater access to many technological services that may not have been accessible to all South Africans before.
Why is SA migrating right now?
The world as a whole endeavours to move in the same general direction when it comes to technology. We want to advance as an entire human race and so when some new or improved way of doing things is developed it is globalised and made popular until it eventually becomes an international standard. This is why digital migration is currently being implemented worldwide and the International Telecommunications Union has signed a treaty with European and African countries to switch over on an agreed timeline.
Countries that have already switched off their analogue transmissions are France, USA, UK, Sweden, New Zealand, Finland and Mauritius. The big concern and need for compliance is that analogue and digital signals interfere with one another. South Africa has signed a treaty stating that analogue signals will no longer be protected (or have precedence) over digital signals after 2015 and so the switch-over to digital will soon become vital to maintain good TV reception.
Important things to know when connecting
Do not purchase a Set Top Box that does not have the official tick of conformance. While there are many independent manufacturers of Set Top Boxes (especially internationally) that may be of good quality or have good prices, there are risks that come with purchasing Set Top Boxes that do not have official approval by the Digital Dzonga Council. These devices may not live up to South African standards and you may experience problems picking up the national digital broadcasts, making the device useless to you.
When purchasing, look for the conformance tick of approval:
The government also plans to set up the Scheme for Ownership Support (SOS) to families who cannot afford to purchase a Set Top Box. Unfortunately, there has been many delays with regards to manufacturing as the government, Multichoice and other involved entities dispute many of the details of the migration. You can still keep updated on new developments and progress through the Digital Dzonga Council website, www.godigitalsa.co.za and through their contact centre: 0800 46 3444 (GO DIGI).
Understanding Analogue TV by Marshall Brain
Digital Dzonga Council Press Releases