"Mrs. Lynnette Annabel Smith" writes:
> I often wondered what was meant by closed caption.
Closed captions are captions at the bottom of the screen
that are invisible to people without special decoders or who
have turned their decoders off.
They make use of exactly the same sort of technology
used by your teletext system but in a completely different
manner.
It turns out the beginning of closed-captioning in the
US goes back much further than one might think. In 1970, there
was a failed project by the governmental body here that deals
with all sorts of standards. The NIST or National Institute of
Standards and Technology wanted a way to deliver precise time
data via part of the vertical retrace interval which is a pulse
sent between each video frame to help televisions synchronize
the scanning process.
While the project flopped, someone got the idea that
ASCII data could be encoded containing short captions viewable
by deaf persons who used special decoders. That way, the
captions wouldn't interfere with the picture if one did not need
them.
Tests in 1972 demonstrated that this was possible but
not much happened for many technical reasons.
By 1980, the decoder chips had become less expensive and
it was possible to manufacture decoders that looked like cable
boxes that individuals who were deaf could buy and read the
captions.
The deaf community wanted this technology in the main
stream and eventually a law was passed in 1990 requiring that
televisions whose picture tubes were 13 inches or larger must
have closed-caption decoders built right in. It turned out that
the manufacturing cost had come way down and the decoders were
now a relatively insignificant part of the cost of a set.
Just like descriptive audio, there has been a lot of
political action by the deaf community in the United states to
get closed captions added to as many local and national
broadcasts as possible.
I remember speaking to an engineer at one Oklahoma City
television station in the early eighties and he told me that at
the time, they did no local closed captioning and didn't even
have a studio monitor that could receive the captions. They just
retransmitted the network feeds, some of which were
captioned and just counted on the fact that as long as their
video signal was good, they were retransmitting the captions.
A television station in Tulsa was one of the first to
start captioning their news. They used volunteers who were court
stenographers that could keep up with the voices on the air so
that deaf viewers saw the captions just seconds after the words
were spoken.
I seem to recall that in Oklahoma City, it took a public
demonstration as in marchers with signs, etc, to persuade at
least one of the television stations to get an encoder and get
busy captioning.
Nowadays, an interesting thing has happened. It is not
uncommon to go in to restaurants or bars or other public places
and find a television whose closed-captions are on so that
people who are interested can read the dialog without having the
sound turned up. In other words, adaptive technology has gone
main stream.
Sets now even have such settings as CC1 or CC2 in their
menus. Selecting CC1 might give you English captions while CC2
may be Spanish or some other language.
Sometimes, when we are watching a movie with poor sound,
Beverly will turn on the captions to help understand what is
being said.
Our digital TV standards are supposed to allow tagging
for both descriptive audio and captions.
Martin
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