ATSC Table 3
Michael Robin:
I enjoy reading your articles. In your column Getting from 4:3 to 16:9 on the Broadcast Engineering Web site, you did make one (to some people) faux pas. There is no 720 horizontal format in Table 3 in the ATSC standard.
John Golitsis
Mississauga, Ontario, Canada
Michael Robin responds:
I have several comments as follows:
- Format conversions from 4:3 SDTV to 16:9 HDTV use signal sources as specified by the ITU-R BT.601 Recommendation with a 4:2:2 sampling strategy. Table 1 of the ATSC A53 lists this standard as well as two HDTV standards and refers to them as “Standardized Video Input Formats.”
- The “601” signals using the 4:2:2 sampling strategy have an active luminance sampling grid of 720 pixels by 483 lines. While the 720 sample structure is slightly adhered to, some signals may change the active number of lines to slightly different values. In my example, I used the 720×480 source format.
- The change from 720 horizontal pixels to 704 occurs in the ATSC compressor. Table 3 of the ATSC A53 lists the allowed compression formats. The ATSC document does not explain why 720 is changed to 704 in the compressor. Interestingly, the ATSC A63 version intended for countries using the 625/50 scanning format specifies 720 pixels instead of 704. So, this is another ATSC item needing revision.
In response to the Could Dead Birds Derail DTV? editorial, Broadcast Engineering writer and consultant Don Markley reports:
A few years ago, I had the occasion to testify at a zoning hearing for a new 2000-foot tower north of Des Moines, IA, the third in an existing antenna farm.
Some of the protestors to the new tower presented a paper that had been prepared by either Iowa State or the University of Iowa showing the results of a two-year study of the dead birds around the tower. The protesters used the research to argue that any new structure would simply kill more birds and should not be allowed.
Upon studying the report, we found that none of the dead birds discovered around the towers were on the endangered species list or even presented a concern about their populations. In fact, many of the birds the protesters were concerned about were on the U.S. Department of Agriculture's listing of birds that are considered to be common pests and disease carriers.
We argued that the tower, therefore, provided a valuable public service in reducing the population of those undesirable pests without killing any endangered or concerned species.
While the zoning commission didn't buy our argument as to the public service provided by the tower, they also didn't consider the bird kill to be objectionable and approved the tower.
Is cable preventing HDTV?
Since August of this year, I have been on a list of people waiting for HD boxes from Time Warner cable (located in a large mid-United States city). As of two weeks ago, I was number 492 on a list of 700 or so local people who are also waiting on HD set-top boxes from the cable company. The customer service rep I talked to had no idea how much longer I might have to wait.
This is an improvement over when I first put my name on that list. Then, the customer service rep at the Time Warner office couldn't (or wouldn't) even tell me how long it might take or how many people were ahead of me. In fact, she seemed to want me to stop asking questions and leave as soon as possible.
This time when I called, they had a partial answer for the delay, “They're made by hand.”
Aside from the question of hand construction, this seems like a strange way to do business, especially with this kind of demand. If there are 700 people on the list for an HD STB that will cost them an extra $10 per month into eternity, that amounts to a minimum of $84,000 per year for the cable company. All that money is sitting on the table right now! And, that doesn't take into account the many potential subscribers who may have gotten discouraged and went to DirecTV.
The slow penetration of HDTV is often rightfully blamed on the broadcasters' lack of HD content. But, with major cable companies like Time Warner as the gateway to these programs, it seems hypocritical for the cable industry to claim that it can't (won't) make HD STBs available to the customers who've been waiting months to get them.
SBE Certified Broadcast Television
Engineer
Name withheld on request
