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Digital TV: the battle of the systems

Making decisions about the digital television system that any country adopts is not a simple task. Apart from the technical considerations, the economic and social decisions that this entails must be addressed with the degree of importance and relavance that they demand.

Much more than TV

Of course, the experiences that countries such as Brazil and Argentina have accumulated, the steps taken by Mexico and Chile on this decision, and the permanent information provided by the organizations that promote one or the other system, are fundamental bases that serve as a north for the other countries of the region in the respective process. about the adoption of a digital television system.

Opting for a Digital TV system is not only planning the future development of free-to-air television as we know it today. Due to the characteristics of the technological advances they offer, television takes on new dimensions that far exceed the simple transmission of an audiovisual signal that is received by a receiver or viewer at home, at no cost, at least within the Open TV model that is handled in Latin America. This will make the concept of entertainment much more complex.


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Digital TV offers several levels of application, if you can call them that. The first of these is a free-to-air TV service of better quality than the current television that uses analog signals, in its presentation of standard definition SDTV (Standard Definition). Without leaving aside the option of seeing it in an aspect ratio different from the traditional one such as 16: 9. A second level is the option of interactivity functions, on which a good part of the e-commerce businesses that support free-to-air TV operations, traditionally supported by the business model governed by advertisers, will be based. Thirdly, the advantages in quality, appearance of the image and richness of visual and sound content of high definition television or HDTV (High Definiton Television). And finally, the transmission of information or data, which will make the digital system much more versatile and therefore, will discover a new source of income and varied applications. Apart from this, there is the component of the transmission of signals to mobile receivers, apple of discord among those who advocate one or another alternative of digital television.

The Brazilian experience

The reports of the Abert/Set Group, (an organization created by the Brazilian Association of Radio and Television Stations ABERT, and the Brazilian Society of Television Engineering SET), in charge of carrying out the performance tests of the three systems that exist on offer in the market today: ATSC, of American origin, DVB-T, its European equivalent and ISDB-T, from Japan, yielded conclusions that suggest the adoption of a different system to the American system. These tests involved 17 companies from the public and private sectors, with the support of Mackenzie University, which through an agreement with the Group was responsible for the implementation of a measurement laboratory and the performance of laboratory tests.

The conclusions of this evaluation process were as follows:

* That the ATSC system does not technically meet the minimum needs for the preservation of the sound and image broadcasting service in Brazil, mainly due to its low robustness to multi-route and its low flexibility, compared to the DVB-T and ISDB-T systems.

* The DVB-T and ISDB-T systems are able to meet both the demands of improving or, at least, replicating the reception of current analog channels, allowing the transport of HDTV signals (payload greater than 18 Mbps), in addition to adding new applications for Brazilian broadcasters.

* The ISDB-T system is significantly superior DVB-T both in terms of immunity to impulsive noise, as well as in performance for mobile reception, important to ensure the competitiveness of the sound and image broadcasting service in the future, as well as offering greater flexibility of applications.

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* Despite the technical superiority and flexibility of the ISDB-T system, it is necessary to consider other aspects such as the impact that the adoption of each system will have on the national industry, the conditions and facilities of implementation of each system, the deadlines for its commercial availability, the price of the receivers for the consumer, the expectation of a fall in these prices, so that it allows faster access to all segments of the population. (See report Digital TV Tests published by Grupo Abert/Set)

To this report, the American association ATSC responded with solid arguments about the low transmission power and low altitude of the antenna used for the tests in the city of Sao Paulo, a condition that, for them, harmed the development of the field tests. About the response of the ATSC system in indoor reception, this association questions the possibility of using a sophisticated digital television system with conventional and cheap indoor antennas. According to them, "the rational use of advanced technology presupposes a harmonious balance between its components."

On the other hand, it also questions the considerations given to the samples taken, in which more importance was given to 27 places that represented difficult reception conditions, when the total, statistically representative sample was 127 test sites. ATSC, raised doubts about the procedures used during the development of this evaluation of the systems. According to them, and with the endorsement of a group of professors from the University of Campinas Unicamp, who also responded to the conclusions offered as a result of the Digital TV tests in Brazil, they indicated that "the Set/Abert Group followed the appropriate methodology but presented procedural flaws that favored the modulation tests of the DVB-T system."


Although ATSC does not offer final solutions for transmission applications to mobile receivers, nor does ISDB offer solutions for cable television applications, the tests that were carried out on the transmission and reception of digital terrestrial signals, put under the same parameters technological developments that are not necessarily the same. Under similar test conditions both in the laboratory and in the field, different systems with modulation schemes that vary in their frequencies and behavior, and receivers for these systems of different generations and characteristics were tested. The tests compared the modulation schemes 8-VSB (Vestigial Side Band with 8 levels) and COFDM (Coded Orthogonal Frequency Division Multiplex), with DQPSK, 16-QAM or 64-QAM modulations, in RF band channels of 6, 7 or 8 MHz and 2k, 4k and 8k signals. Of course, at different bit rates depending on the application: SDTV, HDTV, data, internal reception, mobile reception, influence on adjacent channels, influence on current analog channels, etc.

All systems have virtues and defects that do not disqualify them but that must be tested under specific conditions to determine which may be the most convenient for one country or another. It does not mean this, that each country seeks the option for itself and that in this process things like those that derived, for countries like Argentina and Brazil, in a Pal-M analog television system that is not found in other countries, at least in the Americas.

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DVB-T offers proven and used solutions in many countries of the Old Continent, including developments for cable and satellite television, along with the recent launch of MHP (Multimedia Home Platform), designed to address the convergence between broadcasting, telecommunications and computer technologies. In short, created to offer the possibilities of interactive television and e-commerce. For its part, ISDB-T is a Japanese development, which has extensive experience in the production and transmission of analog high-definition television, and the research support of NHK and Digital Broadcasting Experts, DiBEG Group, a company that has the credibility of all these years of experience. Even so, it is a solution achieved on the basis of the DVB proposal, which does not offer solutions for Cable for example, since these are served by DVB and because, in addition, the penetration of these services in the Japanese market is not as important as the models of open and satellite television. On the other hand, ATSC, concentrates its virtues in the terrestrial transmission over long distances and the advanced development for HDTV in fixed transmissions. It does not have the strengths of the other systems for mobile transmission, a very attractive business niche for broadcasters who await with hope the possibility of expanding and extending their commercial and service options through new media.

Brazil's decision is close to being taken and will surely influence the decisions that can be made by the other countries in the region. Although Argentina has already taken the option for ATSC, it continues to be questioned, and some broadcasters are conducting tests with the two systems. Some with DVB and others with ATSC. This evaluation period seems to be awaiting Brazil's final pronouncement.

It should be noted that in the case of Mexico, a country that shares an extensive border with the United States, not only geographically but also commercially, the possibility of uniting the two systems is being studied to end the debate about the performance of each of them. This Solomonic decision would allow him to share the advantages of one and the other, in addition to giving a prompt solution to the matter, a decision that would save time in the implementation of a digital television system for this country, and that inevitably, it would force an early solution to the debate in the Central American countries.

The idea that moves all this development is very similar to what broadcasting has achieved: to always be with the user, viewer, wherever he is. At home, in your office, in your vehicle or on the bus, on your personal phone or on your computer screen. It opens up strong competition for radio networks, and of course, a much stronger one for broadcasters. Television will be more what it was.

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