When Congress blessed the Digital TV (DTV) standards after many years of diligent work by the Grand Alliance, they probably thought they were approving High Definition Television (HDTV). They were not. The shopping basket of approved formats includes, but is not limited to, HD.

When a network station converts to digital -- and all must in a time frame that is basically 9 years -- they will do so by putting an 8-VSB transmitter on air on a new (free) UHF channel (generally.) The process is regimented by decreasing market size and the first stations will be on the air before the end of 1998.

The shopping basket of formats, which is so typical of the process of "compromise" these politically-correct days, allowed the fight that was burgeoning between the computer industry and broadcasters to go away . . . for a while. There are a number of issues between the parties but the basic ones involve interlaced vs. progressive and number of scan lines. The computer industry wants nothing to do with interlaced systems and seems frightened by systems over 1000 lines.

The Most Popular

It seems clear that the broadcasters find the most popular formats from those allowable to be 480P, 720P and 1080I, the numeric being the number of active lines in picture and P/I indicating progressive or interlaced scanning. To put that into perspective, if you have a satellite receiver in operation today you are receiving an MPEG-2 compressed 480I (with a total number of lines, including vertical intervals, of 525.) 480P will look better, with the scanning structure less visible, a higher vertical resolution, but -- to some people who are sensitive to it even at 60 Hz -- there may be more visible flicker on some types of display.

720P will obviously offer a demonstrably higher-quality picture and 1080I will exactly resemble the 1125 pictures you may have seen at the start of the whole HDTV debate, because that is the total number of lines in a 1080 system. Quality of 1080I is directly comparable to 35-mm film display but with less inter-frame movement-jitter, unless the original source is film.

The big question is what are the broadcasters going to do with their free channel? Not one broadcaster in the U.S. opted out of accepting the channel allocation, though they could have done so. Can the little station 25 miles away from me afford the $500,000 investment in a new tower, new transmitter, 525-to-480P converter, etc. No. What I am sure will happen is that there will be a considerable consolidation of stations, as has, and still is, happening in radio, with most of the smaller market stations taking a satellite feed with a few opt-outs for a Joe Blogg's Motors commercial and the like. Those local materials may well be still produced in 525 component analog and converted to 480P with a line doubler before being digitized.

Who Makes Money?

The right arena to be in broadcasting for the next seven-to-ten years is making UHF transmitters; the second is to be in the business of putting up steel from ground to antenna. Those people are going to make a lot of money although there will be massive movements of customers from terrestrial to satellite and some to digital cable: if those companies can move between trial to real service more quickly than they are doing and without the crazy premiums being charged.

But the excitement by the broadcasters is puzzling. What exactly are they going to transmit in their 8-MHz of channel space? The minimum legal requirement is to transmit one 480I DTV signal, but most will supply a minimum 480P. Or they could transmit one 1080I HDTV signal. CBS and PBS are the only networks to come out and say that they are committed to HDTV transmissions; they don't say how much of the programming. A panel at NAB (next month, Las Vegas) has been set up with the heads of engineering of all the networks who are going to talk about program formats. That all of them will be able to transmit HDTV is beyond dispute and that, I predict, is the only clear sound bite we will hear from this panel; it really needs the Corporate Managers to be up there making the statements to confirm program formats.

But if they don't transmit HDTV what will they put in the bitstream they are not using for the compressed 480P transmission? There are lots of ideas of how that capacity could be used to make money and without defined systems being announced your ideas are at least as good as, and probably better, than mine.

It is particularly interesting that the enthusiasm of the U.S. commercial broadcasters is not shared by their counterparts in Japan. The National Association of Commercial Broadcasters has come out with direct statements about terrestrial implementation putting some its members out of business. That is pretty direct stuff and they obviously don't have the same ideas about making money out of the bandwidth (sorry, datawidth,) or the Americans have not shared them.

Production Formats

There are completely different battles going on in the video production world. Most broadcasters and broadcasting-supply production houses seem to be of the opinion that the highest-possible quality should be used in the initial production so that the library is perfect. You can transmit the material at any lower grade. At later dates, as transmission formats improve, the archived material will still be of use; the value of that material will be retained or increase. That is very logical to me, so the first option would be to produce and store in 1080I uncompressed. Second choice would be the same format but with light compression and that is the way a number of conservatives are going. But it is expensive.

Of the Japanese equipment manufacturers the two bellwethers are Sony and Panasonic. Sony seems to be gambling on 1080I but I suspect they could turn a fast heel if they have it wrong. Panasonic seem to be 720P-oriented. Or at least they were . . .

NHK, the public TV network in Japan, has elbowed itself right into the argument; NHK with "Hi-Vision" was the precursor of the 1080I standard, albeit fully analog, and have an ax to grind in its furtherance. The organization has applied pressure to companies like Panasonic not to demonstrate 720P production equipment at NAB. (My mind kind of boggles how any one organization, save the Government, has the power to really apply pressure to a company the size of Panasonic.)

That little maneuver has not gone down well at the some DOD operations in the U.S. where 720P has basically been accepted as the de facto standard for commercializing quite a bit of the imaging work that has been developed.

Nor are the PC channels thrilled; they see 720P as being the best for PC use.

There are also a number of pundits who have been hoping that commercialization of the new terrestrial channels would be by having two program channels, most of the time, one at 480P and one at 720P; then, when material was available, a single HDTV transmission would be made for that program's duration and then back to the double channels. I personally don't think we have enough program material to cover the existing terrestrial and cable channels, and I don't understand where all the additional advertisers are going to come from. Additionally, broadcasters such as NBC have been quietly laying down hints that they don't care for 720P. (NBC, coincidentally has been one of the major purchasers of Panasonic equipment for the last decade.)

Whatever, DTV is coming and there are rich opportunities for analog engineers to be involved at the baseband and RF ends of the systems. What will make people pay for an HDTV receiver is something else; it has always been my contention that you can't sell technology: but if Monday Night Football was available only on an HDTV channel you would have no problem selling HDTV receivers at virtually any price.

By: Paul McGoldrick
Sr. Technology Editor, EDTN

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