The Transition to HDTV Broadcasting in Europe
Europe is finally making the leap into HDTV broadcasting, which could have a large impact on the flat-panel-display industry. Here is a look at the current state of the rollout and the steps it took to get here.
by Dietrich Westerkamp
WHEN COMPARED to the rest of the world, Europe has lagged behind in the introduction of HDTV broadcasting services. That rollout is currently taking place across the continent. However, each country in Europe seems to be approaching HDTV broadcasting in a different way, making broad-based observations for the implementation of this technology difficult. Still, one fact holds true for all European countries: the first commercial HDTV services in all of them were launched on satellite. In some countries, cable was next to introduce HDTV, while, in others, it was terrestrial broadcasting. It has been nearly two decades since the concept for analog HDTV broadcasting was first broached in Europe, and in order to understand the current state of the various rollout strategies, it is important to look back at how Europe arrived at this juncture.
In 1990, during the course of the Advanced Television (ATV) program in the U.S., General Instruments proposed the first all-digital high-definition-television (HDTV) transmission system. This demonstration stimulated many of the competitors in this U.S. program to look into digital systems. It became obvious relatively quickly that the new ATV system for the U.S. would be a future-proof digital system.
At the same time, various European research projects were started to look into the technologies needed for all-digital transmission of TV and HDTV.1–3 Nevertheless, the focus of European HDTV system developments at that time was on HD-MAC, the European analog transmission system for HDTV services. However, the D2-MAC system that was intended to provide the foundation for HD-MAC failed for various reasons. Once D2-MAC had failed, a new approach was needed for HDTV in Europe, but for a variety of reasons the process of finding a new approach was put on hold for some time. One reason for the lack of urgency was the unavailability of economic HDTV receivers with a high enough on-screen resolution.
Under the umbrella of the European Launching Group for Digital Terrestrial HDTV (ELG), a technical discussion group called the Working Group on Digital Television Broadcasting (WGDTB) was formed in 1991. The focus of this group was a system that could be used in a hierarchical fashion. Within the transmission channel, a data stream would be decoded as HDTV for the large high-quality TV set in the living room, and part of the same bit stream would feed a smaller TV set with a standard-definition picture. In fact, the report issued by WGDTB4,5 in 1992 details this concept of a digital hierarchy (Fig. 1) reaching from HDTV over EDTV (extended-definition TV) and SDTV (standard-definition TV) down to LDTV (limited-definition TV) for portable and mobile devices. The first work on this concept focused on the terrestrial transmission channel.
Fig. 1: Concept of a digital hierarchy.
In 1993, the WGDTB became the European Digital Video Broadcasting (DVB) project.6 This project was organized in modules (commercial, technical, intellectual property rights, and promotion), governed by a Steering Committee and a General Assembly. From the very beginning, representatives of all groups involved in digital TV were present: broadcasters, manufacturers, network operators, and regulators.
The main reason for the success of this project is believed to be the strict rule that no technical work can be started before a definite study of the commercial requirements has been done. This rule caused interest in HDTV to decrease rather quickly because major segments of the industry pointed out that the digital transmission of more channels in SDTV was of far greater commercial importance then HDTV. This being said, the technical work focused on transmission mechanisms for satellite and cable, and the prime application on these two transmission paths was SDTV. DVB did not undertake the development of data-compression standards for video and audio – instead, the existing Moving Picture Experts Group (MPEG) stan-dards were adopted. One technical group in the DVB context defined guidelines for the use of MPEG coding standards to implement European TV services.7 At all points in time, this included HDTV as the highest quality level.
Starting with pay-TV services via satellite in 1994, DVB-S digital TV was introduced in Europe. The major benefit seen in the market was the increased number of programs with improved quality – but still in standard definition. The cable transmission standard DVB-C was adopted second, with the terrestrial DVB-T being the last of the classical transmission paths. Here, the results of all of the basic research work1–3 were brought into the DVB project, and the technical working group came up with a unified European standard.8 For all transmission links, the video- and audio-coding method was MPEG2 taken from the worldwide family of MPEG standards.
For terrestrial transmission, a multi-carrier system based on orthogonal frequency-division multiplexing (OFDM) was chosen.8 This modulation and multiplexing method allows for the operation of single-frequency networks (SFN) that help to use the existing spectrum as efficiently as possible.
After a long debate, the DVB technical group decided that a simple simulcast of HDTV and SDTV would be almost as efficient as any hierarchical coding to support multiple levels of image quality. In addition, it was much cheaper to realize in products. This finding led to digital SDTV services all over Europe because the commercial interest lay in an increased number of programs and not higher resolution.
On the other hand, the standardization work in the DVB context always included the necessary parameters for HDTV.7 But it took some years before the commercial requirements for HDTV became evident. The arrival of new technologies for HDTV flat-panel displays as well as new mechanisms for video-data compression (MPEG4/AVC) and digital transmission (DVB-S2) stimulated the HDTV debate in recent years. National HDTV forums were founded in many European countries. These forums brought together the stakeholders that were interested in introducing HDTV services.
One of the major discussion topics was the choice of scanning format. Contrary to the large variety of scanning standards that were adopted by ATSC in the U.S., in Europe this debate focused on the duality between 1080i/25 and 720p/50. In the long run, the progressive standard may be upgraded to 1080p/50 but, as of today, this is still not yet economical. The European Broadcasting Union (EBU) did intensive studies and proved the superiority of progressive scan for digital-video compression,9 and therefore recommended that 720p/50 be used for the introduction of HDTV services with the option to upgrade to 1080p/50 in the years to come. The first HDTV service rollouts by public-service broadcasters using 720p/50 have been announced (SRG in Switzerland, ARD/ZDF in Germany).
The pay-TV operators and commercial broadcasters all chose to use 1080i/25 for their initial HDTV rollouts. This has been mostly a commercial decision because the viability of these operations depended largely on content (mainly movies) from overseas where the 1080i standard prevailed. When it comes to sports coverage, the preference for 1080i is no longer that evident because the progressive 720p standard offers better picture quality.
All in all, the final choice of HDTV scanning standard(s) for Europe is not absolutely unique because commercial arguments differ in part from arguments for technical superiority. From the point of view of the receiving devices, this was taken into account when the European Trade Association (EICTA) published minimum receiver functionality requirements,12 where the support of both standards was made mandatory.
HDTV Introduction via Satellite Pay-TV Services
In Europe, satellite, cable, and terrestrial TV are regarded as different transmission infrastructures, but not necessarily completely different businesses. Starting from the initial terrestrial broadcasting with only a few public-service broadcasters, the start of satellite broadcasting saw the appearance of private, advertiser-financed broadcasters. And when the cable infrastructure started to cover the bigger cities of Europe, the same programs were fed 1:1 into the cable networks that "just" served as another transmission means. At that time, all signals were analog PAL and only some RF modulation parameters were changed.
The analog-to-digital transition of broadcasting started in the satellite domain, when the French pay-TV operator, Canal+, began the first digital transmission in 1994. The development of the terrestrial DVB-T standard took somewhat longer and the introduction of digital terrestrial TV started later when the first digital terrestrial pay-TV service, On-Digital, was launched in the U.K. This operation failed economically and a re-launch as Free-View finally brought a successful start to services based on DVB-T in the U.K. In the meantime, DVB-T services were also launched in other European countries, mostly with free-to-air programs only. In the area of Berlin (Germany), the first analog switch-off occurred in August 2003. Since then, several regions in Germany have been completely converted to digital terrestrial TV. However, terrestrial transmission currently is used by only about 8% of the German population. The remainder is served by cable (around 60%) and satellite.
The latest television transmission infra-structure in the digital era, IPTV, is gaining in importance. The move to Internet Protocol (IP) as one of the major backbones of the multimedia age and the availability of fast wire-line transmission technologies (xDSL) has led to the first successful commercial IPTV service rollouts in France, Italy, and the U.K.
Pay-TV operators drove the commercial start of HDTV services in Europe on satellite. Most obviously, on satellite, bandwidth was available to allow for additional HDTV programs. The technological progress described above made HDTV services economically viable and the 2006 football (soccer) World Cup in Germany was a key event used to start commercial HDTV services on a larger scale. In fact, pay-TV operators (Premiere in Germany, BSkyB in the U.K., and Canal+ and TPS in France) advertised their offerings extensively. At the IFA 2005 trade show in Berlin, two German private free-to-air broadcasters (Pro7 and Sat1) announced that they would start commercial service just ahead of the pay-TV offerings. Unfortunately, their start – though a very effective marketing event – was not so successful because the HDTV-capable set-top receivers were not available in the needed quantities due to a shortage in some of the required silicon.
As of today, HDTV programs from satellite are available in many European countries. Most of them are pay-TV. Figure 2 illustrates a rough sketch of current offerings.
Terrestrial HDTV Rollouts
The map of digital terrestrial TV services in Europe is rather scattered. Situations differ widely in the various countries. While some are largely cabled (the Netherlands, Belgium, and Germany) and have only very few remaining terrestrial viewers, others have a much bigger terrestrial audience (France and U.K.). There are also largely different legal and regulatory requirements. In some countries such as France, there is a political position to have HDTV available over terrestrial channels, while in others, such as Germany, there is a clear position that, in the near future, there will be no terrestrial digital HDTV services.
Let us now take a closer look at the situation as of the second-half of 2007.
France: France will be the first country with terrestrial HDTV services. There has been a decision on a law that mandates several features for TV receivers on very short notice. As of the end of 2007, all TV receivers marketed in France must have a DVB-T front-end, and as of December 1, 2008, all HD-ready displays must have an HDTV-capable (MPEG4/AVC) DVB-T front-end. In the transition scenario from analog-to-digital terrestrial transmission, one full multiplex, capable of carrying three HDTV programs, was put aside for HDTV services. A call to prospective programmers has just been finalized and four service providers have responded. The government regulator CSA now needs to decide which three services will be put into the one multiplex to start HDTV services at the beginning of 2008.
Fig. 2: HDTV satellite channels on-air in Europe.
United Kingdom: The U.K. was the first European country to rollout DVB-T services starting with a trial run in 1996 and a full launch in 1998. After the failure of On-Digital in 2002, the subsequent start of Free-View has been very successful. In the second-half of 2006, the BBC did a trial run of HDTV service over DVB-T in the greater London area. The outcome was an overwhelming positive response from the people involved. However, there is currently not enough bandwidth available to start a regular HDTV service. The U.K. is one of the strongest supporters of the DVB technical work on a second-generation terrestrial transmission system, nicknamed DVB-T2, in order to have additional transmission capacity to start HDTV services in the future.
Germany: There is DVB-T coverage of almost 70% of the German population. The frequency planning and DVB-T parameter choices have been made with the idea of coverage for indoor and portable reception. In areas covered by DVB-T, the analog transmissions have been switched off in order to have enough spectrum capacity to accommodate the large number of digital SDTV programs. But there is still more demand. In the end, there is no room for HDTV programs and, due to the focus on portable reception, there is also little interest from the broadcasters. HDTV will reach the consumer in Germany via satellite, cable, and, later on, also via IPTV.
Scandinavia: In Sweden, HDTV services via satellite have been rolled out. Following that, first trials based on DVB-T have been started, but no commercial service exists yet. Norway will start its terrestrial digital TV services soon. Due to the rather late start, they could decide to adopt the more-powerful MPEG4/AVC picture coding from the beginning. They also decided to use MPEG High-Efficiency Advanced Audio coding to allow for bandwidth-efficient transmission of surround-sound signals. Both steps allow the rollout of HDTV services, but, commercially, nothing has been started yet.
Italy: Italy rolled out DVB-T services in SDTV nationwide in 2004. In the area of the island of Sardinia, analog switch-off took place in March 2007. In that context, the private broadcaster Mediaset started the first HDTV service with their channel Retequattro HD.
Spain: Spain also rolled-out DVB-T services widely. In Catalonia, this rollout included an HDTV service with the channel TV3, which began in April 2007.
HDTV-Related Logo Programs
Large-screen flat-panel displays have been on the market for quite a while in European countries, but not all of them are really capable of HDTV display, causing some consumer confusion. For this reason, the European CE trade association EICTA12 defined HDTV-related product logos (Fig. 3).
The first logo, called "HD ready," was published in January 2005. It identifies consumer display devices that can display HDTV images from a receiving device connected to them. A set of minimum requirements needs to be met, such as a minimum screen resolution (at least 720 physical lines), the avail-ability of digital (DVI or HDMI) as well as analog (YPrPb) interfaces, the processing capability for both European HDTV standards (720p/50 and 1080i/25), and an implemented content-protection mechanism (HDCP). HD ready was very well accepted in the marketplace, and by the end of 2006 more than 130 worldwide companies representing more then 200 product brands used the logo. Virtually all display devices with screen diagonals of 26 in. and above were HD ready.
The second logo, "HD TV," was developed to identify HDTV-capable receiving devices, which gave consumers the confidence that the set-top boxes they purchase "understand" the signals coming from the receiving antenna. Most obviously, DVB-S2 needed to be implemented as well as DVB-S for legacy reasons. The decoding hardware must support MPEG4/AVC as well as MPEG2 for video. And last but not least, Dolby AC3 surround sound had to be supported.
Not all boxes do carry this logo because pay-TV operators wanted to promote their own branding. But as of today, almost 100% of the HDTV-capable set-top boxes are meeting these minimum requirements.
HDTV is being rolled out in Europe much later than in some other parts of the world. This has the advantage that the most-efficient technologies (DVB-S2, MPEG4/AVC) can be used to provide a better commercial trade off. Due to the different local situations in various European countries, the conditions for HDTV services differ quite a bit. In any case, the first commercial services in all European countries were launched on satellite. Terrestrial rollouts were second or third and, in some countries, will most probably never exist.
The new satellite modulation mechanism DVB-S2 was one of the reasons why HDTV services could be rolled-out with good commercial success. This led the DVB organization to look into the possibility of having a similar next-generation transmission technology for terrestrial channels. This new standards activity (named DVB-T2) is currently in a very busy phase of evaluating a large number of contributions that have been made following a call for proposed technologies. Before the end of 2008, DVB should come up with a new standard proposal for more-effective transmission over terrestrial channels. This may be the point in time where some more European countries will revisit the idea of introducing HDTV service in the terrestrial domain.
Last but not least, the success of HDTV services is largely dependent on the program offerings to consumers. The technical equipment and the regulatory framework being in place, the program content will determine the adoption rate of HDTV in Europe.
1P. G. M. de Bot et al., "An Example of a Multi-Resolution Digital Terrestrial TV Modem," Proc 1993 IEEE International Conference on Communications 3, 1785-1790 (1993).
2H. Amor, J. Hagenauer, R. Kays, G. Möll, F. Müller-Römer, R. Schäfer, U. Sieben, D. Uhlig, and D. Westerkamp, "HDTV-T: A Joint Research Project on Digital Terrestrial Broadcast of HDTV," International Workshop on HDTV 11, 18–20 (1992).
3P. Appelquist, "HD-DIVINE: A Scandinavian terrestrial HDTV Project," EBU Technical Review Summer (1993).
4WGDTB 1063: "Report to the European Launching Group on the Prospekts for Digital Terrestrial Television" (November 1992).
5U. Reimers, "European Perspectives on Digital Television Broadcasting: Conclusions of the Working Group on Digital Television Broadcasting (WGDTB)," EBU Technical Review (Summer 1993).
7ETSI TS 101 154 V1.7.1 (06/05), "Implementation Guidelines for the Use of MPEG-2 Systems, Video, and Audio in Satellite, Cable, and Terrestrial Broadcasting Applications."
8ETSI EN 300 744 V1.5.1 (11/04), "Framing Structure, Channel Coding, and Modulation for Digital Terrestrial Television."
9H. Hoffmann, "HDTV – EBU Format Comparisons at IBC-2006," EBU Technical Review – The Best of 2006.
10ETSI EN 302 307 V1.1.2 (06/06), "Second- Generation Framing Structure, Channel Coding and Modulation Systems for Broadcasting, Interactive Services, News Gathering, and Other Broadband Satellite Applications."
11ISO/IEC 14496, "Information Technology – Coding of Audio-Visual Objects – Part 10: Advanced Video Coding."