DTH is one of the most promising areas of entertainment in India with a large market that has welcomed many players. There are 6 players-Dish tv, DD Direct Plus Tata sky, Sun direct, Airtel, Big tv and Videocon at the time of writing this post.
But most of us dont understand how this technology actually works and how it effects our tv viewing experience. The whole process from uplinking of the signal to viewing on our tv goes through so many steps that there may well be several seconds of delay between the time a live event happens and the time it comes on our screen!
Lets compare the whole thing with the mango business that starts at the farmer and ends at the consumer's plate!
To enter this business, you need the Government's permission that has several guidelines to be followed.
1. Getting content/feed from the broadcaster: This is like a seller buying mangoes from a farmer. No one is going to give it for free. Usually, content providers[channel owners] charge the DTH company for every subscriber that they have. So if a DTH company has 5 million subscribers, they need to shell out the package price multiplied by 5million.
2. Compressing the signal for transmission: Imagine this to be somewhat like minimizing the transportation costs by arranging the mangoes in a proper way so that there is minimum requirement for the number of trucks or number of trips to the consumer market.
In DTH world, the signal is compressed to MPEG2 or MPEG4 format[which consumes lesser bandwidth than MPEG2] which helps them to use lesser bandwidth while sending the signal to the satellite high above in the sky.
3. Protecting the signal from theft: This is like protecting mangoes from smugglers/mango thieves. They need to be transported in a tightly sealed container.
Here encryption of signal works as the seal, using an 8 byte secret key called a control key!
4. Receiving the signal by the consumer: The signal is received by the outdoor dish antenna and LNB[Low Noise Block] and sent to the STB [Set Top Box] thats kept indoor. This is similar to displaying the mangoes in an attractive pyramid like heaps where you and your father go to buy. Even though you see the mangoes, you cant have them yet!
5. Decryption of the signal by the STB: This is the tricky part of the whole thing. You cant understand anything if you steal any of the signal now. You need to have a card that can use the signal and decrypt/decode it. Its like opening the hard seal that usually accompanies the carry bag of Big Bazaar--Not easy!
The signal has 2 important part that helps the card inside STB to decode: ECM[Entitlement Control Message] and EMM[Entitlement Management Message]. ECM is like the key using which you open a box. EMM tells the card if it should ever decode the signal or not Its like a permission, similar to your father telling you to "open" or "not to open" the mango box!
Once you have paid the subscription amount and as long as you have balance in your account, you can have the permission[EMM] from your father and open the box using the key[ECM] and have the mangoes!
EMM also decides which channels you are given access to and which not[Based on the add on packs that you may/may not have purchased].
The problem with EMM right now in several systems like Sun Direct is that they are sent at very long intervals because of which even if you subscribe to say Star Movies, HBO and Sony PIX, your STB decodes the signal only after 8 hours after purchase[As has happened to me].
6. Showing the decrypted signal on the TV: This is something which is very usefull even for an old tv with hardly 30 channels.
Since STB controls the channel navigation and sends the output in only one specific bandwidth, you dont need your tv to have a huge capacity of channels.
All it needs is either:
An antenna point and capacity to show just one channel,
or
just 2 AV points[1 for the audio and 1 for the video input].
So it shouldnt surprise us if there is a delay of few seconds in all this DTH business!
Anil
