| Introduction
In the nearly
four years since the first digital stations began their
ATSC broadcasts, the digital television market has
evolved rapidly. Initial transition costs for stations
could easily exceed $2M, and many wondered how medium
and small market stations would ever find the money
to fund the transition.
One small
way in which the cost of transitioning could be reduced
was transmitting a limited version of PSIP. While you
may have chosen to launch with a dynamic PSIP system
from the beginning, static PSIP became a popular way
for stations with a single channel of programming to
get on air for considerably less investment. The mandatory
tables (STT, MGT, EIT, TVCT and RRT) were transmitted,
although some were not populated, and set top boxes
were able to decode the signals.
Closed
Captioning and Static PSIP
As of July
1, 2002 the FCC required manufacturers of digital television
(DTV) receivers and DTV set-top converters to include
DTV closed captioning display functionality in DTV
devices shipped or manufactured in the United States.
As broadcasters you are now required to transmit this
closed captioning information, though the first products
have just started to reach consumers.
This deadline
also signaled another change in ATSC transmissions--the
beginning of the end of static PSIP. ATSC standard
A/65A entitled "Program and System Information
Protocol
for Terrestrial Broadcast and Cable (Revision A)" defines
the manner in which closed captioning information must
be presented in an ATSC compliant stream. Specifically,
on page 36 of that document, it states "…if the
video service does not carry television closed captioning,
the caption_service_descriptor() shall not be present
either in the Program Map Table or the Event Information
Table."
In short,
closed caption information must be presented on a program-by-program
basis. Static PSIP, by its very nature, doesn’t have
the ability to automatically recognize or change information
of this kind, which at best means that an operator
would need to do it manually every time there is a
program change.
Why not simply
set the closed caption descriptor to always indicate
the presence of closed captions, even when they aren’t
present? The newest devices shipping into the market
continue to look for the information and some have
had issues that eventually required a manual reset
of the device by the consumer.
This issue
has, at most, accelerated the demise of static PSIP
by only a few months. Amendment 3 to the above-mentioned
A/65A standard, approved April 1, 2002, implemented
the Redistribution Control descriptor. At it’s most
basic, the intent is to signal whether or not a consumer
is going to be given the ability to record the program
he or she is watching. Again, the descriptor has to
be set on a program-by-program basis based on contractual
agreements with rights holders. While this hasn’t been
implemented yet, the Broadcast Protection Discussion
Group has provided a framework toward an agreement
on how this capability can be used.
TANDBERG
Television will continue to provide the ability to
run static PSIP in its encoders, since that functionality
is embedded in the software itself. However, given
that we know continued use of this functionality could
possibly create an issue, it is our strong recommendation
that some form of dynamic PSIP generation system be
implemented.
Without it,
you run the risk of being fined by the FCC for not
providing closed caption capability.
General
Release
Issue 1.0 first published Sep
12 2002
www.tandbergtv.com
Author: Lisa Hobbs
Published: September 12, 2002
Click
here for printable version (PDF)
|
