In this article you will learn:
- Basics of digital broadcasts
- Need to buy converter boxes even if already on Pay TV and
- Pros of Digital Broadcast over Analogue Broadcast
Unless some major happening interfere with the planned digital migration, political or otherwise, we can confidently say that by 13th December 2013 all analogue TV signals will be switched off in Nairobi and its environs. Three months later Mombasa, Malindi, Nyeri, Meru, Kisumu, Webuye, Kisii, Nakuru and Eldoret will be switched off; that is by 30th March 2014. Then everyone else will follow suite in the analogue signal switch off by 30th June 2014. For the press release of the switch off read Digital Migration- Nairobi Analog signal to be turned off on December 13th.
The digital migration talk has been with us for a while and people have asked several question ranging from the differences between the digital TV broadcast and analogue TV to whether someone with a LED flat screen TV should buy a separate converter box. In this article we attempt to address these questions starting from the basics of TV broadcasts, whether to buy a converter box if you have pay TV like Dstv, Gotv, Zuku or StarTimes, to giving you the link of where you can get the converter boxes.
Digital TV Broadcast
Our TVs are made to receive radio waves and decode the information (images and sound) encoded in the waves for screen display and speakers. For analogue transmission, the broadcaster takes the image of the scene for broadcast, converts that image to electric signal, modulates the signal to the radio wave frequency as allocated to him, and sends out the signal as a radio wave. The antennae connected to your TV will receive the radio waves and as vibrations send them to your TV, which, according to the set tune of the tuner in the TV, will determine the correct wave frequency to decode into pictures and sound. To send the signal via waves in this manner takes up a lot of bandwidth (a range of frequencies) of the wave; 6 to 8 MHz of bandwidth to be precise.
Although radio waves are the widest in the electromagnetic spectrum from as low 3KHz to as high as 300GHz, the available spectrum for TV broadcasting is quite limited to VHF and UHF-30MHz to 3000MHz (see this document for frequency allocation for different communication needs). In addition, for each TV channel, there must be a blank channel band between two channels (white-spaces) to avoid interference.
This is where the digital broadcast comes in. Instead of modulating the images taken from the scene into radio waves, digital broadcast first converts the images into a series of 1s and 0s, providing a mechanism whereby the signal can be compressed into tinier data streams (MPEG-2 format) that can be carried over by the same waves at the rate of about 20Mbps. Normally without the noise in analogue transmission the useful data carried over by analogue broadcast is about 5Mbps or less so for the same bandwidth, digital TV can carry four times more information compared to analogue transmission.
The fact that a bandwidth can carry four times more information also means that for the same bandwidth, one broadcaster can decide to operate four sub-channels airing four different programmes at the same time. The ability to send out four programmes within the same bandwidth is made possible by a technique called multiplexing. Anyway at the time your TV receives the 1s and 0s to the tune of 20 million 1s and 0s every second, it needs to convert them back to pictures. But as mentioned earlier, the TV were made to decode the analogue data sent to it as a composite signal so the 1s and 0s will look like gibberish to the TV. That’s where TV converter comes in.
Digital TV Converter
There are two types of converters: the ADC (Analogue-Digital Converters) and the DAC (Digital-Analogue Converters). ADC is the converter that is embedded inside your digital camera to convert the analogue real life picture to a stream of 1s and 0s stored within your camera’s SD card as an image. Similarly, when you have music stored in the SD card but you want it to playback as real life song, you need to convert the 1s and 0s in the SD card to audible sound through DAC. This also applies to watching digital movies. When you have a movie stored as 1s and 0s and you want to watch, your computer and smartphone through DAC applications like Windows Media or VLC Media Player together with the necessary video/audio drivers, will convert the strings of 1s and 0s to motion pictures and sound. These software and drivers are the computer’s DAC. Your TV does not have these software installed so you need to have a physical converter. Some TVs have inbuilt converters and we’ll visit them shortly.
Since the TV lacks the “software” to convert the 1s and 0s into picture and sound, you need to buy a physical DAC. To avoid a very lengthy article, we will review some of the top boxes available in Kenya in later articles. For now you can get the list of approved top boxes from this link. It is a pdf format so you will have to download it. The document has converters as cheap as Kshs 4,000 (I thought the cheapest ought to be Kshs 800?) to real deals that you can buy for over Kshs130K. They have also included prices of iDTV if interested.
I am on Pay TV, should I buy a Top Box?
Yes and No. No because the Pay TV providers already offer the conversion for you before transmission and will continue transmitting digital content as they receive them from the broadcasters. Yes because watching free to air on pay TV is not free. If you don’t pay you will only watch KBC. The alternative is to buy new free to air decoders from Zuku, Dstv, and StarTimes according to this report and this other report. The latter report indicate that our current decoders for Zuku and Dstv will not be able to receive the free to air channels after the switch off. “This means that the subscribers will have to either invest in new gadgets that convert analogue signals to digital format or buy upgraded decoders from service providers like StarTimes and GOtv”, writes Business Daily.
Gotv seems to have responded to the requirement of offering free to air for free by offering a new bouquet where subscribers pay a one time fee of Kshs. 2,600 ($300) to access the Free to Air without having to pay monthly subscriptions.
More of this section in a later article.
I want to buy Integrated Digital TV Instead
According to this page on HowStuffWorks, it is better to buy the components separately. The reason they have given is that the standards for digital TV broadcast is still in a volatile phase where regulators change them way too often. That means if the standards change in next one to two years, you will be required to buy a whole TV set or go through an expensive process of changing the inbuilt tuner (if changeable).
Having addressed some of the important issues concerning Digital Migration, what benefits can we expect from the Switch Over?
Sound and picture quality
The analogue broadcast uses the strong-dimming-off signal sequence and for continued quality, the broadcaster must ensure that at all times the signal arriving at the TV is strong. Because he cannot always assure this, the picture quality will most of the time range from strong, shadowy, snowy, blurry, to off. Digital TV is an off-on technology hence whenever the signal is on, you will constantly receive best quality of both picture and sound. Sound wise, with analogue you unlikely to experience the clarity and surround effect of a digital broadcast.
Digital broadcast also allow broadcasters to send images in their original 1080p resolution (if available) without having to “crop” them to fit the analogue’s 512p resolution which compromises on quality. That is, you will be able to watch wide screen movies just as they were originally produced.
As I had mentioned before, digital broadcast allow broadcasters to do what they call multiplexing where they can broadcast up to 4+ programmes within the same channel’s bandwidth. For example K24, having launched as 24/7 Kenya’s news channel, can go back to airing news 24/7 in one of their sub-channels but bring the other programmes in other sub-channels. Also, Citizen TV might want to dedicate one sub-channel for Tusker Project Fame 6 throughout the day as they continue with their normal programming in other sub-channels. Whenever different live events are taking place at the same time, the stations will have no reason to split the screen but could instead air each live event on its own sub-channel. This will be great for channels like KBC that like airing sports action.
Clearing up resources
We have described how broadcasting digital content will free up the white-spaces. The telecos in Kenya are eagerly waiting for these white-spaces to be available so that they can offer better broadband coverage for majority of Kenyans. Other guys who would benefit from the white-spaces are the security officers and the fire fighting guys (do we have them in Kenya?).
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