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4K introduction scenario for terrestrial TV A hybrid & scalable approach

Raoul Monnier, September 2015

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ABBREVIATIONS .............................................................................................................................................. 3

1. INTRODUCTION ............................................................................................................................................. 5

2. THE SECOND DIGITAL DIVIDEND ..................................................................................................................... 5

3. HYBRID BROADCAST/BROADBAND DISTRIBUTION .......................................................................................... 6

4. SCALABLE CODING ......................................................................................................................................... 8

5. BENEFITS OF 4K SCALABLE/HYBRID DISTRIBUTION .......................................................................................... 9

5.1 ASSUMPTIONS ......................................................................................................................................................... 9

5.2 BROADBAND NETWORK LOAD AND CDN STORAGE REDUCTION ....................................................................................... 10

5.3 REACH INCREASE .................................................................................................................................................... 10

5.4 FLEXIBILITY AND SMART BANDWIDTH USE ................................................................................................................... 13

6. NEXT STEPS ................................................................................................................................................. 14

7. ACKNOWLEDGMENTS .................................................................................................................................. 14

8. CONCLUSION ............................................................................................................................................... 14

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ABBREVIATIONS

4K Ultra-high definition format (3840 × 2160 pixels)

APAC Asia and PACific

API Application Programming Interface

AVC Advanced Video Coding

BL Base Layer

CDN Content Delivery Network

DASH Dynamic Adaptive Streaming over HTTP

DVB Digital Video Broadcasting

EL Enhancement Layer

EMEA Europe, Middle East and Africa

H2B2VS HEVC Hybrid Broadcast Broadband Video Services (Celtic-Plus project)

HbbTV Hybrid Broadcast Broadband TV (promotional initiative for hybrid digital TV)

HD High Definition

HEVC High Efficiency Video Coding

HM HEVC test model and reference software

IEC International Electrotechnical Commission

ISO International Standards Organization

ITU International Telecommunications Union

MPEG Moving Picture Experts Group (working group of ISO/IEC)

MV Motion Vector

OFCOM Office of Communication (independent regulator and competition authority for the UK

communications industries)

OTT Over The Top

PAT Program Association Table

PCR Program Clock Reference

PES Packetized Elementary Stream

PID Packet IDentifier

PMT Program Map Table

SHM Scalable HEVC test model and reference software

SHVC Scalable High efficiency Video Coding

STB Set-Top Box

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SVC Scalable Video Coding (AVC)

TEMI Timeline and External Media Information

TS Transport Stream

UHD, Ultra-HD Ultra High Definition

UHF Ultra High Frequencies

URL Uniform Resource Locator

VCEG Video Coding Experts Group (Question/Working Party/Study Group of ITU-T)

VHF Very High Frequencies

WRC World Radiocommunication Conference

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1. INTRODUCTION

TV channels and broadcast operators are facing a major challenge to introduce 4K services for terrestrial

television. Spectrum scarcity due to pressure from mobile operators to release UHF frequencies is today

preventing them from launching 4K channels, despite the fact that Consumer Electronics products are ready

and experimental transmissions have demonstrated the technical feasibility of 4K terrestrial broadcasting.

Combining scalable coding and hybrid broadcast/broadband distribution offers a way to meet this challenge.

HDTV transmissions over terrestrial networks remain unchanged and an enhancement layer is sent over the

Internet to allow the TV set or STB to decode and display the 4K picture.

After reviewing the evolution of TV spectrum resources, this paper introduces hybrid distribution and

scalable coding. It then outlines the benefits of scalable/hybrid distribution, and finally presents the next

steps to consider in order to help introduce 4K on terrestrial television.

2. THE SECOND DIGITAL DIVIDEND

At the start of the World Radiocommunication Conference in 2012 (WRC‑12)1, the African and Arab groups

tabled proposals for a new mobile allocation immediately below the existing 800 MHz mobile band. WRC‑12

concluded with a decision to create a new mobile allocation in the band from 694–790 MHz (known as the

“700 MHZ band”), in ITU Region 12, which is proposed to come into force in 2015. ITU has begun a significant

work program of technical studies on two important agenda items for WRC‑15 (Geneva, November 2–27,

2015).

In Europe, the result of this decision is the re-allocation of terrestrial multiplexes, with attempts to keep

existing services but very little chance of adding new ones such as 4K.

As Digital Terrestrial TV broadcasting is regulated by national bodies, the situation is different from one

country to the next. The situation in France is described below as an example of a European country where

terrestrial broadcast is widely used.

In April 2016, France will stop broadcasting digital terrestrial TV in MPEG-2. Consequently, the “700 MHz

band” will be freed up for future use by mobile communications operators. The transition to MPEG-4/AVC

will also result in a reorganization of the multiplexes, which will be reduced from eight to six. The use of

MPEG-4/AVC and the improved performance of video encoders will expand the bouquet of channels in high

definition, with five HD channels per multiplex, as demonstrated by Thomson Video Networks in December

20143. However, there is no room for 4K channels in this multiplex reallocation process. This would require

further reorganization with the introduction of DVB-T2. And this is certainly not set to happen for many years

to come!

1 See more: https://itunews.itu.int/En/3744-The-second-digital-dividend-Another-bite-for-mobile.note.aspx 2 Region 1 comprises Europe, Africa, the Middle East west of the Persian Gulf including Iraq, the former Soviet Union and Mongolia. 3 https://www.thomson-networks.com/en/news/thomson-video-networks-presenting-france%E2%80%99s-first-dttv-demonstration-delivery-five-hd-channels

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The other big challenge in freeing up the 700 MHz band for mobile use is to determine an appropriate band

plan that will facilitate harmonization with other world regions. International harmonization of the 700 MHz

band could be achieved, but not without detailed cooperation between the different ITU regions, given the

current divergence in 700 MHz deployments between the United States and parts of the Asia-Pacific for

instance.

In the United States, the pressure is even greater than in Europe. The 700 MHz band was released back in

2008 and the U.S. Federal Communications Commission is ready to hold the incentive auction of broadcast

TV airwaves in early 20164 to free up the 600 MHz band and repackage those airwaves to sell to mobile

operators. The auction is considered the agency's most complex undertaking to date, balancing economic,

engineering and political considerations.

Broadcasters will have several options to choose from. They may:

Continue broadcasting as is, but be subject to a channel change, Move from UHF to VHF to free up higher-band spectrum, Share a channel with one or more other stations, Distribute without terrestrial broadcast, concentrating on cable, satellite, or online channel

distribution, Go permanently off the air.

So far, no US broadcaster has announced plans for 4K on terrestrial television!

3. HYBRID BROADCAST/BROADBAND DISTRIBUTION

Worldwide connected TV shipment volume in 2015 is estimated to be in the 40%-50% range. However,

applications running on these TV sets are today practically limited to providing links to content providers’

applications such as catch-up TV services over the broadcast channel. The full potential of hybrid

broadcast/broadband TV distribution is therefore not exploited.

The main objective of H2B2VS5, a Celtic-Plus6 project coordinated by Thomson Video Networks, is to develop

successful hybrid network solutions that enable value-added services with optimum bandwidth usage in each

network. One of the use cases studied by the project7 is the transmission of Ultra-HD TV by sending HD

content over the broadcast channel and the required complementary video over the broadband network.

The two streams are then combined in the terminal to display a 4K picture, as shown in Figure 1.

4 See more: http://www.pwc.com/en_US/us/industry/entertainment-media/publications/assets/pwc-broadcast-spectrum.pdf 5 See more about the H2B2VS project: http://h2b2vs.epfl.ch/ 6 Celtic-Plus is a EUREKA Cluster focusing on ICT and telecommunications: https://www.celticplus.eu/# 7 See more use cases here: http://h2b2vs.epfl.ch/wp-content/uploads/2013/04/H2B2VS-D1.2.6-Updated-report-on-use-cases-V1.1.pdf

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Figure 1 – Hybrid transmission of 4K content

One challenge of the project was to design a robust, frame-accurate synchronization mechanism working

with two different networks that offer unequal quality of service with significant differences in delay and

jitter.

All deployed broadcast TV networks rely on the MPEG transport stream to synchronize programs and their

components. The Transport Stream uses its own clock, called the Program Clock Reference (PCR), to ensure

accurate synchronization of the components. The PCR and time stamps associated with each component are

not related to the original media time of the content. Hence, they may not be known by the service

packaging the broadband media streams and they may be modified by network equipment such as

transcoders. This is why they cannot be used as a reliable way to synchronize the broadcast and broadband

networks for video services.

The H2B2VS project suggested an approach which consists of embedding a timeline into the broadcast

stream. This “TEMI” timeline was successfully proposed for standardization in MPEG and also adopted by

DVB and HbbTV8. Figure 2 shows how the TEMI descriptor is contained in an MPEG-TS as a “pointer” to

external media carried by the broadband channel. A TEMI descriptor, carried in the adaptation field of the

Transport Stream, essentially contains timestamps and location descriptors providing the URLs of the

currently running associated extension or upcoming ones.

8 It is described in HbbTV V2.0. The section devoted to APIs for media synchronization provides an example of broadcast channel synchronization with a DASH stream delivered over broadband relying on use of the TEMI descriptor.

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Figure 2 – TEMI descriptor in the MPEG Transport Stream

4. SCALABLE CODING

Scalable video coding is not a new concept. However, it was not previously used for TV broadcasting because

it required complex implementations at both the encoder and decoder ends. When defining SHVC9, the

scalable extension of HEVC, MPEG paid special attention to keeping it simple, even if slightly less efficient

than SVC, the scalable extension of AVC. For this reason, it was chosen by the H2B2VS project for

implementation of the 4K/hybrid use case.

SHVC defines tools to provide spatial, fidelity, bit depth, and color scalability. The SHVC encoder consists of

several HEVC encoders, one encoder for each layer. The first layer is the Base Layer (BL), followed by multiple

Enhancement Layers (ELs). For 4K spatial scalability, the base layer encoder encodes a version of the 4K video

which is downsampled to HD and then feeds the 4K enhanced layer encoder with the decoded picture and its

Motion Vectors (MVs). The 4K enhancement layer encoder delivers a higher resolution video, using the

decoded picture from the lower layer as an additional reference picture. The inter-layer reference picture is

upsampled and its MVs are upscaled to match the resolution of the layer being decoded.

9 SHVC was finalized in July 2014 by the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG). For more details, see document “Scalable HEVC (SHVC) Test Model 8 (SHM 8)”: http://mpeg.chiariglione.org/standards/mpeg-h/high-efficiency-video-coding/n14971-scalable-hevc-shvc-test-model-8-shm-8

MPEG-TS

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Figure 3 – Block diagram of an SHVC encoder (two layers, 2x spatial scalability)

5. BENEFITS OF 4K SCALABLE/HYBRID DISTRIBUTION

5.1 Assumptions

Thomson Video Networks carried out investigations into the bitrates needed to encode the base layer and

enhancement layer and compared them with the requirements for broadband/simulcast transmission with

HD and 4K programs encoded using a non-scalable approach. The HD stream would be broadcast on the

terrestrial network and the 4K stream sent over the broadband network (OTT services). For this purpose,

SHM10 and HM11 HEVC Reference Software were used. The bitrates needed for HD-quality and 4K-quality

pictures were evaluated. Table 1 shows the results which were adjusted to take into account the progress to

be expected in professional HEVC video encoders in the coming years.

Hybrid scenario Simulcast scenario

Bitrate sent on the terrestrial network

(base layer)

Bitrate sent on the broadband network (enhancement layer)

Total Bitrate sent on the terrestrial network

Bitrate sent on the broadband network

Total

3.5 Mbps 8 Mbps 11.5 Mbps 3.5 Mbps 11 Mbps 14.5 Mbps

Table 1 – Bitrates for a hybrid and simulcast approach

10 See SHM repository here: https://hevc.hhi.fraunhofer.de/svn/svn_SHVCSoftware/branches/ 11 See HM repository here: https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/branches/

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5.2 Broadband network load and CDN storage reduction

The primary benefit of the hybrid/scalable approach is the approximate 30% reduction in the bitrate of the

broadband network and storage capacity of the CDN when compared to a simulcast scenario.

Smart cooperation between broadcast and broadband networks is the answer to the “Internet capacity

crunch” problem identified by some scientists12. The cables and fiber optics that deliver data to users may

have reached their limit by 2023 and Internet power consumption may become critical, for instance using all

of Britain's power by 2035, according to Professor Andrew Ellis of Aston University in Birmingham.

5.3 Reach increase

The hybrid/scalable versus broadband/simulcast scenario also helps to increase the number of end users able

to receive 4K programs.

Akamai recently published its 7th “State of the Internet” report for Q4 201413. The following study is based on

the data provided in this report. Figure 4, Figure 5 and Figure 6 respectively show the cumulative percentage

of connections in EMEA, APAC and the Americas. From this data, the percentage of connections above 8

Mbps and 11 Mbps was extracted. This is shown in Table 214.

Figure 4 – Cumulative % of connections in Europe, Middle East & Africa

12 See Daily Mail, May 2, 2015, “Is the internet on the brink of collapse? The web could reach its limit in just eight years and use all of Britain's power supply by 2035, warn scientists” http://www.dailymail.co.uk/sciencetech/article-3064915/The-Internet-reach-limit-just-eight-years-warn-engineers.html 13 For details, download the Akamai report here: https://content.akamai.com/PG1380-SOTI.html 14 Countries with very poor Internet were removed from the statistics as it did not make sense to envisage 4K video over broadband.

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Figure 5 – Cumulative % of connections in Asia Pacific

Figure 6 – Cumulative % of connections in the Americas

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Table 2 – How the number of end users receiving 4K is increased with a scalable/hybrid approach

In sum, using a scalable/hybrid approach improves 4K reach by nearly 20%.

In most cases, the lower the Internet quality, the higher the improvement. For instance, the increase is 26%

in Thailand.

Country/Region

Average

Connection

Speed (Mbps)

% Above

8Mbps

% Above

11Mbps

Reach

increased by

AMERICAS Average gain: 18%

United States 11.1 51% 35% 16%

Canada 10.7 54% 34% 20%

Uruguay 5.9 28% 9% 19%

APAC Average gain: 18%

South Korea 22.2 84% 75% 9%

Hong Kong 16.8 70% 56% 14%

Japan 15.2 67% 52% 15%

Singapore 11.7 54% 36% 17%

Taiwan 10.6 53% 33% 20%

Australia 7.4 34% 14% 20%

New Zealand 7.3 37% 13% 24%

Thailand 7.1 37% 11% 26%

EMEA Average gain: 19%

Sweden 14.6 60% 44% 17%

Netherlands 14.2 68% 51% 17%

Switzerland 14.5 68% 51% 18%

Romania 11.6 66% 49% 18%

Norway 11.4 50% 32% 18%

United Kingdom 10.9 53% 35% 18%

Czech Republic 12.3 55% 37% 18%

Denmark 11.9 60% 39% 21%

Finland 12.1 54% 36% 18%

Belgium 10.8 58% 38% 19%

Ireland 12.7 45% 30% 15%

Israel 10.6 58% 36% 22%

Austria 9.8 46% 23% 23%

Hungary 8.7 46% 25% 21%

Poland 8.8 45% 23% 22%

Russia 9 47% 25% 21%

Slovakia 8.2 36% 18% 18%

Spain 8.2 41% 20% 21%

Portugal 8 42% 22% 20%

Germany 8.8 43% 21% 22%

France 7.1 33% 13% 20%

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This is confirmed by a study undertaken by OFCOM in the United Kingdom in 201415, as shown in Figure 7.

The improvement is higher (≈ 20%) in rural areas - where connection speed is low - than in urban areas (≈

10%). In rural areas, the number of end users who would receive 4K is roughly doubled when using

scalable/hybrid transmission.

Figure 7 – Distribution of broadband speeds in the UK, by population density

5.4 Flexibility and smart bandwidth use

Using the Internet to complement programs which are sent over terrestrial networks also gives broadcasters

more flexibility. This is a genuine advantage in the “first age” of 4K.

Programs produced with 4K definition are still relatively rare, particularly when it comes to live programs. If

you dedicate a terrestrial channel to 4K full time, you can decide to broadcast native 4K programs with a

limited choice of content - which may bore the end user - or upscale HD programs to 4K before broadcasting

them - which is definitively not a smart use of bandwidth!

With a scalable/hybrid approach, there is no misuse of the terrestrial spectrum and the enhancement layer is

sent over the Internet only when it makes sense to broadcast 4K.

On the one hand, as for many years the HD layer will still draw the most viewers, it is more economically

efficient to use broadcast technologies. On the other hand, several economic studies have confirmed that

broadband delivery offers flexibility but has a higher per-user cost than broadcast delivery when the number

of viewers is above a certain threshold. Using hybrid technology to provide 4K is an optimum solution as long

as 4K does not become mainstream.

15 See OFCOM Infrastructure Report 2014: http://stakeholders.ofcom.org.uk/binaries/research/infrastructure/2014/infrastructure-14.pdf

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6. NEXT STEPS

The results presented in section 5 are based on HEVC coding for both the base and enhancement layers.

However, in the perspective of an introduction of 4K services with a scalable/hybrid approach, compatibility

with the existing HD standard (MPEG-4/AVC 1080i/25 in Europe) should be considered.

In the block diagram in Figure 3, the HEVC encoder of the base layer is replaced by an AVC encoder. The 4K

Enhanced Layer encoder is still fed with the decoded picture but the motion vectors are not used as HEVC

and AVC motion vectors differ significantly.

Preliminary simulations conducted by Thomson Video Networks confirm that this approach is relevant, even

if the enhancement layer needs a slightly higher bitrate due to the fact that the base layer relies on interlaced

pictures containing half the number of lines. More investigations are needed to define the appropriate

bitrate on the 4K enhancement layer.

7. ACKNOWLEDGMENTS

The work described in this white paper is supported by the European Celtic-Plus project H2B2VS and was

partly funded by Finland, France, Spain, Switzerland and Turkey.

The author would like to thank TDF, Arkena, IETR/INSA and Télécom ParisTech for their cooperation in

demonstrating 4K scalable/hybrid distribution.

8. CONCLUSION

Without cooperation between terrestrial broadcast networks and the Internet, the introduction of 4K

programs on terrestrial networks seems very unlikely.

A scalable/hybrid approach is a way of facilitating the introduction of 4K. Compared to simulcast distribution

of HD on terrestrial networks and 4K over the Internet (OTT), bandwidth and storage capacity saving on the

broadband network is about 30%. In addition to cost saving for TV channels and network operators,

scalable/hybrid technology would help to slow down the energy consumption of ICT networks which is

doomed to skyrocket as video consumption is predicted to explode.

This hybrid approach would also increase the number of end users eligible for 4K by 20% when compared to

a standard OTT solution, thus improving return on investment.

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15 Copyright 2015 Thomson Video Networks. All rights reserved. All other trade names referenced are service marks, trademarks, or registered tr ademarks

of their respective companies. Specifications subject to change w ithout notice. CDT-5253D

Last but not least, this approach is a smart way to cope with the limited amount of 4K content available

today, which avoids broadcasting a 4K channel with novel content 24/7. In this case, the enhancement layer

is sent over the Internet only when it makes sense to broadcast 4K.

These results were obtained by considering HEVC/SHVC coding. Additional studies are needed to fine-tune

these figures in order to address legacy issues.

The work described in this paper is part of the research effort by Thomson Video Networks to provide its

customers with solutions to increase their business revenues with a possible scenario for introducing 4K

services.

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