Dan Griffin <dgriffin@webaccess.net> wrote:
> Does anyone know how "The Weather Channel" distributes the regional
> forecast information (as seen during the "local on the 8's" portion)
> to the local cable companies. Is it data in the vertical interval of
> the TV signal, or do they use internet connections (broadband,
> dial-up), or some other communication channel?
The local-weather data is distributed by satellite along with the
primary video signal. It's distributed simultaneously over several
different satellites in different formats; a list of more-or-less
current assignments is at http://www.lyngsat.com/amc10.html (scroll
down to Weather Channel).
Three typical cases:
AMC-ll transponder 13 (3960 MHz, Vertical)
http://www.lyngsat.com/amc11.html
Video is distributed as analog NTSC; audio, local-weather data, and
other metadata are encoded on subcarriers and the combined signal is
encrypted with the VideoCipher II scrambling system. At the headend,
the signal is decrypted with a VideoCipher II decoder and sent to a
so-called "Weather Star", a proprietary (and very expensive)
rack-mounted PC that decodes the local-signal data and inserts it on
cue in place of the default video (maps of various parts of the
country showing rudimentary forecasts) received from the satellite.
If the Weather Star is not used, default video passes through. This
format is now all-but-obsolete, but presumably it's still available
for the benefit of smaller CATV systems and the lodging industry, many
of whom don't use Weather Stars.
AMC-10 transponder 24 (4180 MHz, Horizontal)
http://www.lyngsat.com/amc10.html
Video, audio, local-weather data, and other metadata are multiplexed
into a single data stream which is then encrypted with the DigiCipher
scrambling system. At the headend, the signal is decrypted and sent
to a digital version of the Weather Star. This format is now used by
most CATV systems and many high-end hotels and casinos.
DirecTV 1R/2/4S unknown transponder
http://www.lyngsat.com/dtv101.html
Video, audio, and metadata, along with several other video signals and
their respective audios and metadata, are all multiplexed into a
single data stream which is then encrypted with the DirecTV's
proprietary scrambling system and modulated onto one of DirecTV's
transponders. There is no local-weather data; all DirecTV subscribers
get the default video. Echostar (Dish Network) uses a similar
proprietary scheme. Presumably, Voom did so too before it ceased
operations.
Neal McLain
Neal McLain (nmclain@annsgarden.com)