The Impact of MPEG-2

 Last update: 2003/08/08

The radio spectrum is sliced for use by a multitude of services and the VHF/UHF band assigned to terrestrial television broadcasting is very narrow. Spectrum scarcity used to make television a great business to be in, first because the number of broadcasters in any given market is reduced to a handful of Service Providers (SP). and second because the business has been given the means to sustain itself: public broadcasters could impose on citizens owning a receiving set the payment of a license fee and commercial broadcasters could rely on advertisements as a source of revenues. Some countries even have the best (so to speak) of both worlds: public broadcasters not only charge license fees, but they can also get further revenues from advertisements. 

That easy life began to change in the 1980s when some SPs, fancying what at that time seemed to be a virtually infinite bandwidth, started using satellite for television broadcasting. All of a sudden the number of simultaneous programs, until that time reduced, could easily grow by at least an order of magnitude. Practically, however, those wanting to watch satellite TV had to put up with annoying disruptions in their homes and make substantial expenses in antenna, wiring and STB. Not really a deterrent, but the viscosity of habits established during decades of TV viewing works wonders. 

If there were some relaxed faces in broadcasting companies, there were also concerned people who understood that digital television was still years away, but one day it would come and that day the wind of change would blow like a hurricane. On that day the number of television programs that could be broadcast on the terrestrial network would become, say, 5 times as many. Great news, you would say. Not really, I say. 

The business of a broadcaster is fine tuned to provide its audience programs, either self-produced or acquired, with a degree of attractiveness (somehow related to cost) such that the audience is sufficiently high to entice advertisers and provide revenues to offset the cost of operation and program production or purchase. Leaving some positive margin is, of course, more than desirable. But if one day digital Fairy Morgana suddenly multiplies the number of channels by a factor of 5, are the revenues going to multiply by 5? This is not likely, both for the public and the commercial broadcasters. On the cost front, network managers will have to manage 5 times the transmission capacity, but the operation cost of the physical infrastructure will hopefully be multiplied by less than 5. On the other hand, program production and purchase costs are probably going to have something near to a 5-fold increase, if the level of program quality remains the same. The conclusion is that finding a new equilibrium point in multichannel terrestrial television may be hard.

Some people are more forward-looking than others. Instead of mourning the eventual demise of their business, NHK engineers set out to develop a new television system, which they called HDTV, with a bandwidth 5 times standard television's. In doing this they were simply continuing the broadcast engineering tradition of extending the capabilities of television, which had begun with the introduction of colour. 

The model set by NHK, CCIR wranglings notwithstanding, found other converts. The MAC solution pursued by Europe was clearly less bold than Japanese HDTV, but HD-MAC looked like a solution that combined the best of both worlds: an evolutionary path that targeted the eventual goal of HDTV while providing an immediate, compatible improvement to today's televisions. 

A similar pattern of goal setting drove the American broadcasters but with a very different implementation. A move by the FCC to change the 700 MHz band allocated to television broadcasting over to cellular telephony, triggered the request by the broadcasting industry to upgrade the general USA broadcasting technology field. By requesting an evolutionary path to HDTV, that industry not only secured the status quo in the existing frequency allocation, but succeeded in putting an option to yet another portion of spectrum, the one used for the differential signal to provide HDTV. 

Given the background, one can understand how the worldwide broadcasting industry must have watched with trepidation what was being done by this uncontrolled group of technologists gathered under the name of MPEG (and I would indeed subscribe to the word "uncontrolled", if I think of some of the active figures in that group, some of the deeds of one of which I have already told) to provide a digital television broadcasting standard. But, as much as the blue-suit people from IBM made a deal with that group of long-haired programmers working for what would become the Microsoft we know today, so the worldwide broadcasting industry sort of "made a deal" with the uncontrolled MPEG technologists. As an aside, it is worth remembering that, in the best tradition of these technology deals, the deal that MPEG "signed" was non-exclusive. 

Ronald Bedford, then with the Independent Television Association in the UK, Taiji Nishizawa, then Director of the NHK Science and Technology Research Laboratories and Chairman of CCIR SG 11/B, and Robert Hopkins, then the Executive Director of ATSC, attended all the critical meetings in which MPEG-2 took shape. They did not so much attend the Video group where the "uncontrolled" ruled, as the Requirements group who set the guidelines for the development of the technology. 

Much as the blue-suit people from IBM did not question the low-level DOS function calls that the long-haired Microsoft employees of those early years were defining, so these gentlemen from the worldwide broadcasting industry did not question the prediction modes or packet field choices that the MPEG technologists were making in the red-hot Video and Systems meetings. But in the end the MPEG-2 standard provided all the functionalities that this industry requested - by no means in a homogeneous fashion - and at no detriment for the functionalities that other industries demanded. 

The second customer came from an unexpected quarter. In the USA, where analogue satellite broadcasting had not taken hold at all, Hughes Electronics was aggressively working on a major digital satellite broadcasting project called DirecTV, later to become a separate company. For this initiative the MPEG-2 compression, far from a curse, was a blessing because it lowered the cost of developing the digital technology, enabling a wider offering of programs than could ever have been realised before because of spectrum scarcity and hence service cost. Against all odds DirecTV turned out to be a significant success.

The third customer came from an even more unexpected quarter. In spite of the technical success of European HDTV in the form of HD-MAC, as demonstrated at the winter Olympics in 1992 in Grenoble, Europe started having second thoughts about digital television. At the initiative of Peter Kahl of the German Federal Ministry of Posts and Telecommunication, interested parties started gathering in 1991 as the "European Launching Group" of a "European Project on Digital Broadcasting". The first talks were directed at creating the European equivalent of the American ATV initiative, obviously skipping the analogue prelude. A technical group within the project started mulling ideas about solutions that employed scalable video coding ideas. However, the results, as with scalable solutions already tried in MPEG, were not up to expectations. 

In 1993 the European Project on Digital Broadcasting abruptly decided to redirect its interests to a new direction, viz. digital satellite broadcasting. The political environment, which until that time had been dithering while the project was drafting its charter, finally decided to endorse it. The initiative, under the new name of Digital Video Broadcasting (DVB), was then formally kicked off. 

At the top of the hierarchy there is a Steering Board (SB), a body with a limited number of elected members representing European PTT Administrations and industrial members, not necessarily European. Below it there are four committees, the Commercial Module (CM), the Technical Module (TM), the IPR and Promotion and Communication Modules. DVB takes pride in being "market driven" and therefore the TM undertakes no technical work before the CM considers it from the viewpoint of market requirements and formally communicates its support. Technical specifications produced by the TM are then submitted to the SB for approval, sent to the Comité Européen des Normes (CEN), CENELEC and ETSI, where appropriate, for rubberstamp and published as European Norms (EN). 

In a rather short time, DVB produced the first specification of a complete digital satellite broadcasting system. The audio and video source coding were MPEG-2 Audio and Video, multiplexing and transport was MPEG-2 Systems. The technology specifically developed by DVB was the QPSK modulation scheme for satellite broadcasting. Continuing along this line, DVB later produced modulation standards for CATV (64 QAM) and terrestrial television (COFDM). Other standards produced concern return channels for different media and Service Information (SI), a description of which programs are available where and when. Among the specifications developed more recently is Multimedia Home Platform (MHP). So DVB became another major "customer" for the MPEG-2 standard and the first to adopt the full Audio-Video-Systems trio. 

The fourth MPEG-2 customer is the DVD. In 1994, a number of CE manufacturers and Hollywood studios led by Toshiba and Warner Bros. defined a new CD format, quickly overcoming a competing format by Sony and Philips. The new format could pack more bits than CD Audio by using shorter laser wavelength, finer track pitch and inter-pit pitch, by gluing two discs back-to-back and by allowing the disc to be played at variable speed. A two-hour movie can be stored on one of these discs in MPEG-2 Program Stream where the video part is encoded at variable speed. 

Bits on a DVD may be encrypted. This was the result of protracted discussions between the technology and content companies, the former wishing to develop a format like CD Audio in which bits are cleartext and the latter too wary of providing their bits in a form that would lend itself to an easy copy and distribution when moved to an IT environment.

The fifth MPEG-2 customer was the Japanese broadcasting industry. One should have expected that, with their investments in analogue HDTV, in the land of the rising sun anything digital applied to TV should have been anathema. Not that the development of MPEG-2 should have pleased the bureaucrats at the Ministry of Post and Telecommunication (MPT), but the NHK Science and Technology Center were working on a thoroughly conceived digital broadcasting system called Integrated Services Digital Broadcasting (ISDB). Today MPEG-2 has made substantial inroads in the Japanese landscape with digital satellite broadcasting in SDTV and HDTV. Digital Terrestrial Television is also planned. Japan is probably the only place where the audio component of television is encoded using AAC. 

MPEG-2 is a recognised success. Because of it the audio-visual landscape has completely changed. More than 100 million satellite and cable STBs  have been sold and more than 100 million DVD players have been sold, without counting software players for PC. 

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