The Digital Television Maze

 Last update: 2005/03/08

At the very first meeting in Ottawa, MPEG had set for itself an initial workplan based on three targets: substandard definition television as provided by SIF (1/4 of SDTV) at up to about 1.5 Mbit/s, standard definition television at up to 5 Mbit/s and high definition television at up to a bitrate still to be determined. The first two years in MPEG were devoted to build the organisation and to establish the foundations of the MPEG-1 project. But with the successful execution of the 1989 Kurihama tests and the transition from competitive to collaborative phase at the Eindhoven and Tampa meetings, it became possible to start thinking of the next step. The Turin ad hoc group meeting in May 1990 provided the opportunity to set things in motion. On the evening of the first meeting day I had dinner with D. Le Gall, T. Hidaka, and A. Simon, at the Atlantic Hotel in Turin. The four of us discussed the steps to be undertaken for the next phase of work. 

Disguised, as it might appear under the title "Coding of moving pictures for Digital Storage Media having a throughput of 1.5-5 Mbit/s", the purpose of the project was very clear for broadcasters: MPEG intended to develop a digital television standard starting from the source coding part. This was a very important issue as is clear from some simple arithmetics. Assume that a television channel in the VHF or UHF band occupies a bandwidth of 8 MHz, as is common in Europe (in some PAL/SECAM countries the value is sometimes 7 MHz, while in NTSC countries the bandwidth is 6 MHz) and that a broadcaster decides to offer television programs in digital form. Applying the rule of thumb of 4 bits/s/Hz (i.e. the bandwidth of 1 Hz carries 4 bits/s) one gets a gross bitrate of about 30 Mbit/s. Interesting, but not a big deal, if one considers that digital television per ITU-R Recommendation 656 has 216 Mbit/s, and one would then need to use seven analogue television channels just to carry one digital television program. 

Fortunately video compression comes to help. I have shown before how simple DPCM methods can reduce the bitrate to about 70 Mbit/s, but video compressionists are very smart and they have invented all sort of tricks to bring the bitrate down to about 30 Mbit/s still using DPCM (of course this does not mean that audio compressionists are not smart, simply they are more obsessed with quality because the ear is less tolerant to distortion than the eye). But even so, there is not much to gain by replacing an analogue system that works now and is deployed in 2 billion TV sets with another, incompatible system just for the sake of making it "digital". But if more sophisticated transform-based algorithms are applied, a reduction of some 40 times in bitrate becomes possible and a broadcaster can even squeeze something like 6 TV programs in a UHF channel. 

"What for?" is a question I will deal with later. Continuing with the idea of squeezing more TV programs in the same UHF channel, the problem was that, while designing VLSI chips based on DPCM for video signals looked feasible since early times, designing a chip employing DCT and MC, even for ¼ of TV resolution like SIF, was still a challenge in the early 1990s and the VLSI industry had some hard times trying to make MPEG-1 decoders and, more so, encoders. The complexity remained in spite of all the care that had been put in designing the MPEG-1 standard, and the ability of VLSI designers to design MPEG-1 chips was stretched to its limits. The efforts made for MPEG-1, however, did pay off for MPEG-2 and MPEG-1 can well be considered the stepping-stone for the next, more ambitious MPEG-2 standard. 

The business of satellite broadcasting was even more receptive to the idea of multiplication of channels promised by digital technologies. Ten satellite transponders have a high cost and still only provide a limited choice. But what if they became the vehicle for 60 TV programs? Apart from the obvious multiplication of choice for subscribers, one could think of so-far unthinkable new ways of serving subscribers: the same latest hit movie broadcast simultaneously at staggered times, so that subscribers do not have to wait two hours for the movie to start again; or serving different subscriber communities with diversified interests, etc.

A similar incentive existed for CATV operators. Here several tens of different programs were already the norm since several years past, but the use of digital could enable operators to broadcast hundreds of different programs - 500 was the magic number mentioned by one media tycoon in the first half of the 1990s that caught the fantasy of reporters of that time. If one considers that a cable serves between a few hundred to a few thousand subscribers, it is clear that digital technologies could enable program offerings fine-tuned to match the wishes of the most exacting subscribers. 

So far we have talked of the benefits - or supposed such - for incumbents, but there were other business players stomping their feet to enter this business: the telcos. Stuck for more than a century with a much-in-want and profitable service - telephony - but just that one (indeed, in spite of the early attempts to make it "another" communication service, facsimile turned out to be equivalent to a phone call), they had always wanted to enter the business of sound and television distribution. The former had never been considered very attractive, but the latter was much coveted, even though, or maybe because - as I have already said - it was thought to require a major overhaul of their networks. 

Attempting such an overhaul was not impossible. In the highly regulated telecommunication landscape of the Federal Republic of Germany of the 1980s, Deutsche Bundespost Telekom (DBT) was the only concern allowed by the Federal Law to operate primary television distribution (between studios) and secondary distribution (between studios and broadcasting towers) - nobody else was allowed to do that. Therefore laying and operating CATV was DBT's exclusive prerogative (as it was "secondary distribution"), and they exploited it quite successfully. But this is maybe the only big CATV-related success story in the regulated telecommunication world, if one does not consider the much less successful story of the French Direction Générale des Télécommunications (DGT). Possibly this was caused by the fact - with few similar cases in the world - that a branch of the government was running the telecommunication business. 

What telcos had always wanted was a total overhaul of their network, even though an extension of their business like CATV was second best. The technology existed - optical fibres - what was missing was a great idea for a service that people would be willing to buy and, of course, to have access to the money required to deploy the new network in the hope of a Return on Investment (ROI) in non-geological time. What better idea than millions of television programs and videos stored in gigantic servers, that subscribers could access from the comfort of their homes using the new broadband network? MPEG-2 was the obvious enabling technology component that would have provided an effective way to store, transmit and consume television programs in digital form by using a suitable combination of fibre-based broadband technologies, together with other "shortcuts" like cable or ADSL. 

Before moving on, I must add the CE and IT industries to the list of prospective customers of the MPEG-2 standard. Apart from their obvious interest in making new types of television receivers obeying the wishes of their broadcasting masters, the CE industry was definitely interested in transforming analogue video recorders to digital form. They could even think of using some disc-based recording technology to make some new types of video recorders. The IT industry, instead, was interested in the new MPEG-2 enabled infrastructure with the expected mass deployment of IT-based infrastructure - both hardware and software - replacing traditional television equipment. Lastly there was the growing IC industry, waiting for the new business opportunities created by MPEG-2 encoders and decoders. 

Obviously, the world had not been waiting for MPEG to discover this wonderful business opportunity. If nothing had happened before, it was because of the political stalemate in the CCIR for anything altering the existing television balance, the industry-specific interests of the CCITT and the IEC, and the fact that each of these bodies were populated by a single industry, whose members were more concerned by the possibility that a competitor would gain an advantage, than with the prospects of all sharing (I mean, fighting for) a new business opportunity. 

By virtue of being new, shielded from politics, populated by all sorts of industries and application-agnostic - in addition to having shown its effectiveness in the (at that time still developing) MPEG-1 standard - MPEG was looked at by many as the body that could deliver the holy grail of digital television in the form of a generic standard that all industries could exploit.

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