As cable operators make the digital transition, some are discovering new
ways to deliver analog and digital feeds over the same pipeline, known as
digital simulcast. The goal is to improve the picture quality and services for
analog subscribers, making them less likely to switch to DBS. It also opens up
other advantages: greater bandwidth flexibility and efficiency, and the ability
to splice in hyper-local commercials. Time Warner Cable’s Raleigh, N.C.,
division became the cable giant’s first division to make the move. Pat
Hourigan, VP, engineering and technology, for the division, discussed it with
B&C’s Ken Kerschbaumer.
How does digital simulcasting work?
Basically, the satellite receiver pulls in the different networks and
then sends them to regional hubs. Each channel is then encoded in real time
with 12-14 channels multiplexed together in a single group. A rate-shaping
device then takes that group and gets it ready for ad insertion and ad
splicing. From there, the signal is sent over the digital network to the edge
of the network, where it is decoded to analog for any analog subscribers that
might not have digital set-top boxes.
What’s the advantage?
First, those who have digital set-top boxes receive a pristine picture.
And the picture on the analog set-top is as good as the previous digital
signal. The whole channel lineup looks the same, and all analog-transport
concerns are gone. There’s no more introduction of video noise and
What gear did you use?
We chose Harmonic for the encoder and decoder, Bigband Networks for the
statistical multiplexing and ad splicing, and SeaChange for the digital-ad
What were some of the challenges?
Well, not only were we going digital, but we also put in digital-ad
insertion across five geographic zones. We have 200 channels for splicing in
the ads for those five zones.
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