ATSC standards
Dear editor:
Regarding the September Transition to Digital column, “DTV multichannel transmission,” the master guide table (MGT) and the system time table (STT) are essential. If the first is not correctly constructed, a receiver cannot locate the other tables. The STT contents are critical because sending the wrong time will impact any DVR tuning based on event start times and may impact receivers' ability to actually use the event information tables (EITs). Also, because there is a time accuracy requirement, allowing the clock to drift in the PSIP generator equipment can result in a violation of FCC rules.
The PSIP contains the listed structure for the virtual channel, not the program. Second, the video stream descriptor (which is carried in the program map table for each program) does not contain bit rate or aspect ratio information.
While the major channels in the TVCT (in the United States) can be 2-99, the total number of subchannels that can be signaled is more than 100,000. Early experiments to assign subchannels dynamically caused consumer confusion and few broadcasters to alter the lineup during the day.
The IS disbanded some years ago. Its public findings can be found in the IS Findings subsection under Standards on the ATSC Web page.
Art Allison
NAB
Aldo Cugnini responds:
Thanks for making those important points. As a key contributor to the ATSC standards, your comments should always garner deference. Standards are, by necessity, written in terse and (hopefully) exact language, and efforts to generate short abstracts are challenging to the rest of us.
Bit rate and aspect ratio are, of course, carried in the video sequence header, and my final point was intended to generate involvement in the general activities of ATSC.
3-D TV mind control?
Dear editor:
I am in my mid-60s and an engineering manager retiree from what is now Comcast in Broward County, FL. I was responsible for managing much of the 750MHz/860MHz hybrid fiber and coax rebuild construction that began back in 1995.
Your 3-D article “Just when you thought it was safe …” in the July issue brought back some memories. There was a 1993 made-for-TV mini-series called “Wild Palms” that I became very absorbed in at the time, despite the fact that neither myself nor anyone else was able to follow or understand much of it. In an enigmatic way, it dealt with the introduction of 3-D holographic TV transmission during what I understood would be the 2008 presidential election campaign. The plot, which accorded some pretty sinister motives to the developers/broadcasters and one of the presidential candidates, was suppose to suggest a sci-fi type of mind control plot that never really surfaced. It was only after the series ended that I saw that in the reviews. See www.imdb.com/title/tt0106175/ or http://en.wikipedia.org/wiki/Wild_Palms.
If I get around to it, I may rent the DVD and try watching it again. Anyway, I was just wondering if anyone else who read your back page recalled “Wild Palms?”
Robert J. Matzner
Fort Lauderdale, FL
Anthony Gargano responds:
Glad you enjoyed the column, Robert, but I do not believe 3-D television to be a mind control threat. When 60 million viewers are casting votes on the likes of “American Idol,” it seems to me that mind control is already alive and well in 2-D television!
Go MXF!
Dear editor:
I read your article, “File-based delivery,” in the November issue. Excellent! It's one of those articles that you clip out and keep, which I did.
It was very well-written, concise and informative. Thanks, and keep up the good work!
William M. Quinn
Chair - SMPTE Nashville Section
Technical sales, DNF Controls
Brad Gilmer responds:
Great to hear from you again. Also, thank you for the kind words regarding my article.
All the best, and happy holidays!
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