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KT 4K UHD IPTV Services
July 16, 2015 | By Netmanias (tech@netmanias.com)
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1. UHD Services from Korea Telco KT 4K UHD IPTV Services Live TV, Most Popular Channels Now, 4-Channel View and VoD Dr. Harrison J. Son (tech@netmanias.com) KT launched the world's first UHD IPTV service in September 2014. Now it has over 100,000 subscribers as of May 2015, closing trailing LG U+ who has attracted around 150,000 UHD subscribers over the same period of time. What differentiates KT's UHD IPTV service from its competitors' is that it is the only service that offers not only UHD VoD, but also UHD broadcasting channels. UHD VoD service is available from its competitors, SK Broadband and LG U+, as well, but neither of them provides a UHD broadcasting channel. Then in September 2014, the company began to offer UHD service (encoding rate: 21Mbps, 3840x2160) via its UHD-only channel 'Sky UHD' (450 hours). In addition, since it first applied 'Pre-UHD' technology (encoding rate: 17Mbps, 1920x1080) in April 2015 to upgrade some of the popular channels in Full HD (encoding rate: 9.5Mbps) to UHD-class, KT has provided more semi-UHD channels (We were very satisfied with the video quality of the UHD channel, and I personally did not notice any difference in video quality between Pre-UHD and UHD channels. It apparently is very subjective, though). This year, KT plans to continue to upgrade existing channels to Pre-UHD class. KT is currently offering 3 UHD channels, including Sky UHD2 (130 hours) and CJ UXN (400 hours) just launched in June. Live TV So, we thought it would be worthwhile to take a look at KT's Live TV service (real-time retransmission of broadcast channels over IP network, linear TV channels). First, we will briefly review the history of KT's IPTV Live TV service. KT launched SD/HD-class IPTV Live TV service in January 2009, and Full HD service in December, 2013. KT 4K UHD IPTV Services | Dr. Harrison J. Son (tech@netmanias.com) UHD Pre-UHD FHD SD 201: SkyUHD1 001: SkyUHD2 203: CJ UXN Channel Resolution 3840x2160 Codec H.265 Encoding Rate 21.3 Mbps Network BW 27.1 Mbps 015: JTBC 017: TvN 021: Mnet 028: OCN 058: SBS Sports 1920x1080 H.264 17.2 Mbps 21.4 Mbps 011: MBC 183 channels 1920x1080 H.264 9.5 Mbps 13.5 Mbps 183: E-daily 25 channels 720x480 H.264 3.5 Mbps 4.4 Mbps Drama Series Documentary Movie Category News Drama/Enter. Show/Concert Movie Sports Terrestrial News Frame/sec 30 30 30 30 UHD (3) Pre-UHD (5) Full HD (154) SD (54) Figure 1. KT’s IPTV Channels Information (June 2015) KT IPTV Channels (Total 216 Channels) © Netmanias Consulting • www.netmanias.com • 2015
2. KT 4K UHD IPTV Services | Dr. Harrison J. Son (tech@netmanias.com) Terrestrial Comprehensive PP Home Shopping TvN OCN OCN Series Catch On Catch On + Super Action O’live XTM On Style Story On Tooniverse NGC Baduk TV Chinese TV Mnet KM OnGamenet CJ MediaCJ Powercast CJ UXN MPEG2, FHD (20~30Mbps) 4 streams, 88Mbps (each stream: H.264, 22Mbps) H.264 Live Encoder H.265 Live Encoder SkyUHD1 SkyUHD2 STB KT IPTV UHD STB KT IP Network KT IPTV Headend KT Leased Line PPs H.264, FHD (10Mbps) H.265, UHD (21Mbps) MBC KBS SBS CJ O Shopping NS Home Shopping GS Shop Lotte Home Shopping Hyundai Home Shopping TV Chosun Channel A JTBC MBN H.265, UHD (21Mbps) H.265, UHD (21Mbps) Figure 2. Channels Delivery of KT IPTV (Major Channels) MPEG2, FHD (20~30Mbps)H.264, FHD (10Mbps) MPEG2, FHD (20~30Mbps)H.264, FHD (10Mbps) H.264 Live Encoder Broadcasting Playout Mastertape,schedule H.264, FHD (10Mbps)
3. 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 Nielsen Korea, each using a sample of just about 3,000 households. On the contrary, KT has over 6 million IPTV subscribers. Most Popular Channels Now (9-Channel View) 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 KT 4K UHD IPTV Services | Dr. Harrison J. Son (tech@netmanias.com) Figure 3. KT’s UHD Channels (SkyUHD2) Streaming: Encoding Rate and Required Network BW KT IPTV HeadendKT UHD STB (Kaonmedia) UHD TV (Samsung) 27.1Mbps (IP Multicast Stream) 21.3Mbps (UHD stream) UDP, IP, Ethernet overhead Encryption, FEC overhead 26.3Mbps KT IP Network Network BW 27.1Mbps (wireshark) Streaming Rate 26.3Mbps (wireshark) Encoding Rate 21.3Mbps (content bitrate in vlc) Broadcast stream + CAS overhead + FEC O/H + network overhead Broadcast stream + CAS overhead + FEC O/H Broadcast stream Sky UHD Network BW = 27.1Mbps, CBR, QoS Marking 0x80 * Streaming rate: Refers to the UDP payload rate which can be obtained by subtracting the network overhead (including Ethernet, IP, UDP headers) from the network bandwidth of a multicast stream measured by Wireshark. In general, streaming data includes not only video data, but also other data including encryption information, FEC data, etc. So, the actual encoding rate of a video is lower than its streaming rate. * Encoding rate: Refers to the Content Bitrate value measured in VLC.
4. KT 4K UHD IPTV Services | Dr. Harrison J. Son (tech@netmanias.com) 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 was sent from the STB to KT's network, and just ONE multicast stream ( was transmitted to the STB. Then, when MBC was selected, an IGMP Leave message for was sent out, disconnecting the Most Popular Channels Now stream, and an IGMP Join message for MBC ( was sent out, getting a multicast stream of MBC ( 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 ( So, the answer to our question is ❷. The multicast stream ( has: ŸŸ• Network bandwidth: 6.7 Mbps, VBR • 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: 4.5 Mbps • 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. Figure 4. Screenshot of Most Popular Channels Now (9-Channel View) So, if KT's measurement of viewing rates were based on the data from over 6 million real viewers, 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. UHD STB KT IPTV Headend single multicast stream 9 CHs mixed into one channel ❷ UHD STB KT IPTV Headend CH 1/Multicast stream 1 CH 2/Multicast stream 2 CH 9/Multicast stream 9 ... ❶ Figure 5. 9 or Single Multicast Stream Figure 6. Wireshark Analysis The 9 channels were mixed into one channel in the headend, and then transmitted to the STB in one multicast stream ( MBC ( UDP Multicast Packets IGMP Join ( Ethernet BW: 6.7 Mbps IGMP Leave ( IGMP Join ( Ethernet BW: 13.5 Mbps 9-mixed-CH ( UDP Multicast Packets 9-mixed-CH
5. In a recent test we conducted by using KT GiGA Internet, Samsung's UHD TV and Kaonmedia's UHD STB, we found all 4 multicast streams are transmitted to STB in both cases - whether operator-selected or user-selected. We also confirmed that both options allow for re- arrangement of the channels in the screen. So, a user can move channels around, for example, from the main window to one of the 3 sub-windows, or the other way around. The user-selected 4-channel view also the same results as seen in Figure 7. KT's 4-channel view (operator or user-selected) allows all 4 channels to be independently transmitted in individual multicast streams. As a result, channels can be switched between the main and sub- windows, which makes KT's service different from others'. In summary, KT's 4- channel view service features 3 SD sub-windows (of 3.6 Mbps each, in 720x480) and one Full HD main window (of about 11Mbps, in 1920x1080). Viewing all 4 channels in UHD (3840x2160) is not technically possible, yet. I personally was very satisfied with the quality of the service (both operator and user-selected options). Especially, watching 4 different news channels all at once with a peace of mind that I am not missing any news was a great experience. What I liked about the service most was that I could watch just what I wanted without having to watch all the annoying advertisements. Apparently, this kind of service will change the way people watch TV from now on. 4-Channel View KT also offers 4-channel view service. This service is pretty similar to LG U+'s and has the following two options: 1. Operator-selected channels: Offers a set of 4 channels selected by operator (sports, shopping, over-the-air and movies) 2. User-selected channels (launched in March 2015): Allows users to select 4 channels, and watch them in a customized 4-split view KT 4K UHD IPTV Services | Dr. Harrison J. Son (tech@netmanias.com) Figure 7. Screenshot of 4-channel view Figure 8. Wireshark Analysis We found all 4 multicast streams are transmitted to STB in both cases - whether operator-selected or user-selected. KT's 4-channel view service features 3 SD sub- windows (of 3.6 Mbps each, in 720x480) and one Full HD main window (of about 11Mbps, in 1920x1080) Main window: MBC Sports+ SBS Sports KBS N Sports SPOTV 060: MBC Sports+ Multicast Stream ( 051: SPOTV Multicast Stream ( 059: KBS N Sports Multicast Stream ( 058: SBS Sports Multicast Stream ( 11.2Mbps 3.6Mbps 3.6Mbps 3.6Mbps 060 (MBC Sports+) 059 (KBS) 058 (SBS) 051 (SPOTV) 1920x10 80 720x480 720x480 720x480 11.2Mbps 3.6Mbps 3.6Mbps 3.6Mbps Channels arrangement Resolution Network BW [bps]Network BW Main window MBC Sports+ 1920x1080 (FHD) H.264 8.5 Mbps 11.2 Mbps Sub window 1 SBS Sports 720x480 (SD) H.264 2.5 Mbps 3.6 Mbps Sub window 2 KBS N Sports 720x480 (SD) H.264 2.5 Mbps 3.6 Mbps Sub window 3 SPOTV 720x480 (SD) H.264 2.5 Mbps 3.6 Mbps Channel Resolution Codec Encoding rate Network BW
6. 4K UHD VoD Success or failure of UHD service lies in how much UHD contents the service provided can offer. Being well aware of that, KT has gradually secured more contents, for example, through upscaling of Full HD movies to UHD quality (e.g. 'The Admiral: Roaring Currents', 'The good, the bad, and the weird', 'Masquerade', etc.), through partnership with Sony Pictures for UHD contents (e.g. House of Cards 2 filmed in UHD), etc. A total of 306 UHD VoD contents (300 hours long in total) are currently available for service - 124 free and 182 paid contents. KT 4K UHD IPTV Services | Dr. Harrison J. Son (tech@netmanias.com) Figure 10. KT’s UHD VoD Streaming Of all the 306 contents, we captured the traffic of 124 free contents (by using KT GiGa Internet, Samsung's UHD TV, and Kaonmedia's UHD STB), and found that a HEVC (H.265) codec was used and the frame rate was 30fps. The test also discovered the RTSP streaming protocol was used. The encoding rates were 18.0 Mbps for most of the contents, and 25.0 Mbps for some of them. The contents with both encoding rates were played smoothly. • Codec: HEVC (H.265) • Encoding Rate: 18.0 Mbps (25.0 Mbps for some contents) • Frame Rate: 30 fps • Streaming Protocol: RTSP • Transport Protocol: UDP Following is the captured streaming traffic of 'House of Cards' (Episode 1 of Season 2), an American TV series: • Codec: HEVC (H.265) • Encoding Rate: 18.0 Mbps (see RTSP/SDP in the figure below) • Frame Rate: 30 fps • Streaming Protocol: RTSP • Transport Protocol: UDP • Network BW required: 18.9 Mbps (encoding rate x network overhead), CBR • QoS Marking: DiffServ 0x60 (DSCP 0x18: Class Selector 3) n # of Free UHD VoD 124 # of UHD VoD 306 l Genre 86Movie 111Series 52Documentary 33Life 15Sports 9Performance l UHD VoD Pieces Figure 9. KT’s UHD VoD Contents (June 2015) Sony Pictures, Paramount Pictures, IMAX, BBC, Red Bull, King content, AVA, Daewon Media, Green Narae, etc. l Content Providers Encoding Rate: 18.0 Mbps Ethernet BW: 18.9 Mbps RTSP PLAY [bps] UHD VoD Streaming (House of Cards 2, episode 1) Movie Stream (UDP Unicast Packets)

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