KT IPTV (4K UHD) Service

(1) UHD Live TV

(2) 'Most Popular Channels Now' (9-Channel View)

(3) 4-channel View

(4) UHD VoD

You probably have been switching channels, looking for something interesting to watch, until you finally settle down for one. For viewers like you, KT offers a new way of selecting channels through a service called "Most Popular Channels Now". At the company's Olleh TV home, the following video clip appears when you click the "Most Popular Channels Now".

Of over 200 channels that it is currently offering, KT picks the top 27 channels that are currently being watched the most, and shows 9 channels each time in a split screen as seen in the video clip above, leaving all of them muted except for the one in the red box. Channel selection is updated every 5 minutes according to the viewing rates.  

This service allows you to check what other people are watching the most that moment so you do not miss the fun everyone else is having. It also helps you to get the latest trends in TV shows yourself in real time. It is always good to be able to compare the viewing rates of TV shows, so you can make an informed decision on what to watch. It is always good to be able to compare the viewing rates of TV shows, so you can make an informed decision on what to watch, which can be a very important decision after a long, busy day. 
 
In Korea, viewing rates of TV programs are measured by TNmS and Nielson Korea, each using a sample of just about 3,000 households. On the contrary, KT has over 6 million IPTV subscribers. So, if KT's measurement of viewing rates were based on the data from over 6 million real viewers, apparently the measurements would be a lot more accurate than the other two's, which are based on a much smaller sample.   
 

Now, let's find out ❶ whether each of the 9 channels (displayed in one screen) are transmitted in independent multicast streams, or ❷ whether they are mixed into a single channel in the headend first, and then transmitted in one multicast stream.
 

To find out, we conducted a test. First, we watched the Most Popular Channels Now for about 70 seconds, and then selected MBC. As seen in the figure below, during the 70 seconds, an IGMP Join message for 233.15.200.104 was sent from the STB to KT's network, and just ONE multicast stream (233.15.200.104) was transmitted to the STB. Then, when MBC was selected, an IGMP Leave message for 233.15.200.104 was sent out, disconnecting the Most Popular Channels Now stream, and an IGMP Join message for MBC (233.15.200.55) was sent out, getting a multicast stream of MBC (233.15.200.55) instead. This proves that the 9 channels were mixed into one channel in the headend, and then transmitted to the STB in one multicast stream (233.15.200.104). So, the answer to our question is ❷.  
 

 
The multicast stream (233.15.200.104:5000) has:

• Network bandwidth: 6.7Mbps, VBR
• Streaming rate: 6.5Mbps
• 9 audio streams (of the 9 channels with highest viewing rates) and one video stream (9 channels mixed into one)
• Video codec: H.264
• Encoding rate: 4.5Mbps
• Video resolution: 1280x720 (HD)
• Video frame rate: 29.97 fps

One thing we noticed was that there was about 20 seconds of delay in watching the channels through the Most Popular Channels Now channel (in 9-split screen), compared to watching them through their original channels (just one channel in main screen). This delay must have been caused because i) top 9 popular channels (with the highest viewing rate) had to be chosen from all over 200 channels transmitted to KT's headend in real time, ii) they had to be mixed into one stream, and finally iii) the stream had to be sent to KT's IP network.