How is AFD (for the uninitiated, Active Format Description) in flux?
It's been part of ATSC A/53 since revision c, which was a few years back.
John Willkie
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*From:* opendtv-bounce@xxxxxxxxxxxxx
[mailto:opendtv-bounce@xxxxxxxxxxxxx] *On Behalf Of *Ron Economos
*Sent:* Friday, February 16, 2007 4:04 AM
*To:* opendtv@xxxxxxxxxxxxx
*Subject:* [opendtv] Re: Food for thought
I hear what your saying, "If it's not in the specification,
it's not a bug".
IMHO, it's some fishy stuff. It's actually easier to
decode 720h rather than 704h. 720h matches the
output raster perfectly, while 704h requires that
the image is centered in the 720h output raster
(or at least you're supposed to). So there's an
extra step to decode 704h versus 720h. A decoder
that can do 704h but can't do 720h is totally
counter-intuitive. It's almost like they deliberately
tried to hose it up.
The ATSC's take on this is summarized in the
candidate specification for Annex A:
http://www.atsc.org/standards/cs_documents/CS-TSG-674r1.pdf
From the proposed Table A3 "category" for 720h:
B: These formats were not included in the original Table 3 of Annex A
of A/53,
*but have been in use by broadcasters for several years without
reported complaint*.
These formats are included in Table 3 of ANSI/SCTE 43 2005.
Here's the link for the SCTE reference:
http://www.scte.org/documents/pdf/ANSISCTE432005.pdf
Here in the Bay Area, some of the DTV stations are using
720h. KCSM-DT is 720x480 on their main channel and
KTSF-DT is 720x480 on both of their simulcast (but
different Chinese dialects) video channels.
KQED-DT (the big PBS affiliate) uses 528h on all 3 of their
SD channels when the main channel is HD. KKPX-DT also
has a 528h channel in their multiplex.
What's the holdup on the candidate specification? Is it
political (as you suggested previously), or is it due to
the fact that the AFD and bar data specification is still
in flux? If the candidate specification is never going to
happen, it should be removed from the ATSC website.
Ron
Mark Schubin wrote:
Just so.
TTFN,
Mark
John Willkie wrote:
When doing testing of my PSIP generator recently, my customer found
that a
very recent Zenith DVR (and at least one other recent STB) couldn't
make use
of 720 x 480 video. Not only that, but several other issues disappeared
when he eliminated 720 x 480 video.
IIRC, the Samsung STB had no issues with it, nor did the AutumnWave USB
device.
John Willkie
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx
<mailto:opendtv-bounce@xxxxxxxxxxxxx>
[mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Mark Schubin
Sent: Thursday, February 15, 2007 7:12 PM
To: opendtv@xxxxxxxxxxxxx <mailto:opendtv@xxxxxxxxxxxxx>
Subject: [opendtv] Re: Food for thought
It was long ago, and it's relevant until ATSC changes the compression
constraints. Until that happens, broadcasters need to avoid 720h or
risk hitting TVs that can't receive the signals.
TTFN,
Mark
Ron Economos wrote:
You've posted that many times. How long
ago was that, and is it still relevant?
Ron
Mark Schubin wrote:
During the development of our ATSC DVD recorders
at LSI, *we tested all 36 formats* and much more
(sub-sampled horizontal resolutions, telecine flags in both
1080i and 720p, QAM, bad PSIP, high BER, etc.).
In ATTC's testing, unfortunately, they found two models of DTT
receivers that could not handle 720 x 480 imagery at certain frame
rates (different rates for the two receivers). 720 is not only in
Rec. 601, but it is also divisible by 16. Unfortunately, it's not in
the infamous Table 3.
TTFN,
Mark
