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Reader Feedback - DTV viewers

The Digital Transition Coalition has issued state maps, using FCC data, that illustrate the coverage of digital signals across the nation. Pictured here is New Jersey, showing where some consumers can't receive a signal.

DTV viewers

So, the Digital Transition Coalition says, “Thirty-nine million U.S. households can't get complete DTV service.”

What is more important is that the “Digital Transition Coalition” can't even get their maps right. CBS and NBC national maps are swapped. And, it probably didn't really hurt their cause to completely omit NBC in the largest geographic market in the United States (Utah).

By the way, how can the DTC call itself a “group of consumer organizations,” when we all know who is REALLY behind it, and what he wants to sell?
Ken W. English

Editors' note: Additional information on this issue can be found in the Sept. 27 issue of “Beyond the Headlines,”

Defining “judder”

Dear Mr. Robin,

I recently ran across one of your past articles on the Internet and became interested in the section on temporal resolution. I'm not familiar with the term “movement judder,” and I would like to learn more about it. Actually, I am interested in the whole subject of interline flicker and would appreciate any references you could provide.
Sam Schwartz

Michael Robin responds:

The term “judder” is relatively recent and generally refers to the difficulty that film and television media have in portraying smooth and rapid motion. One old and still annoying example is the film “wagon wheel effect.” Interlaced video suffers from interline flicker, most visible with synthetic video signals such as those produced by character generators. With the exception of such signals, interline flicker is relatively unnoticeable. The vertical resolution rarely exceeds 70 percent of the active video lines, and the watching distance is on the order of six times the picture height. This renders such artifacts invisible. A Google search will reveal a wealth of articles concerning movement judder. As far as interlace in general is concerned, I would refer you to classical television books, such as “Fundamentals of Television Engineering” by Glenn M. Glasford, published by McGraw-Hill in 1955 (!) and “Television Engineering Handbook” by Donald G. Fink published by McGraw-Hill in 1957 (!). Things have not changed much since these books were written.

July Freezeframe:

Q. In 1986, NHK announced a high-sensitivity camera pickup device called the HARP. It was updated to the Super-HARP in 2001. What does HARP stand for and how much more sensitive was each version than a conventional Saticon?

A. HARP stands for High-gain Avalance Rushing amorphous Photo-conductor. HARP was 10 times more sensitive, and the Super-HARP 100 times more sensitive, than a Saticon tube.

August Freezeframe:

Q. What do the following acronyms stand for? ACATS, DVD, MPEG, VADA, THX

A. ACATS:Advisory Committee on Advanced Television Service

DVD:Digital Versatile Disk

MPEG:Motion Picture Experts Group

VADA:Vertical Ancillary Data Area

THX:TomlinsonHolman's eXperiment or George Lucas' first film THX1138 (either is correct)

July Winners:

Patrick O'Brien, KATC-TV
Augusto Villasenor, Globecomm
Fred van Let
Eddie H. Sills

August Winners:

The following people got four out of five correct:

Olumide Ojerinde
Mike Dunlap
Michael L. Scheumann, SCO ENGINEERING
Alex Oluchi
Mark Ferrell, Time Warner Cable

Test your knowledge!

See the Freezeframe question of the month on page 8 and enter to win a Broadcast Engineering T-shirt.

Send answers to