Monday, May 14, 2007
is Switched Digital Video, or SDV for short. Switched Digital Video is a technology that allows cable
TV operators to take better advantage of the existing bandwidth of their cable TV networks. Basically, TV programming- especially now in the digital age- is data, and because any type of cable
has a finite bandwidth, it can only carry a certain amount of TV programming. Of course the amount of
TV programming that a cable can carry depends on what type of cable it is (ie coaxial versus fiber optic
for example) and whether or not the video has been compressed using video compression formats like
MPEG-2 or MPEG-4. But the bottom line is that a cable has a finite bandwidth and replacing a cable
with one with a higher bandwidth is an expensive and time consuming process. That's why cable TV
companies have been losing subscribers to satellite TV companies. Cable TV companies haven't been
able to offer the same number of channels as satellite TV companies and the channels that they do offer
are more expensive per channel than they are with satellite TV companies.
That's where switched digital video comes in. With switched digital video, cable TV companies can
send just the programming that's being watched by a household to that household instead of sending all
of the channels all at once and relying on the viewer's digital receiver to filter out all of the ones that
aren't being watched. This means that the viewer can have a much greater selection of channels
because channels won't be crowded out by limited bandwidth.
Switched digital video is also much better for delivering HDTV than the old "shotgun" approach to
cable TV broadcasting. That's because all other things being equal (length of programming, mode of
transmission, and video compression format) HDTV will require between six and ten times the
bandwidth to transmit that normal standard definition television does. That means that a relatively small
number of HDTV channels could crowd out a huge number of standard definition channels. That said
though, there's no reason why a cable TV company couldn't offer as many HDTV channels as it
wanted using Switched Digital Video. After all, only one channel would be sent over the cable at once
and there's more than enough bandwidth for that.
Anyone who's at all attuned to developing TV technology will see the similarities between switched
digital video and video on demand. There are actually a lot of different ways in which video on demand
can be implemented and switched digital video is definitely a good choice. After all, the ability to
request specific video at a specific time is exactly what video on demand is by definition and exactly
what switched digital video does. Of course, it's a completely different thing from the standpoint of the
cable TV company to make a huge library of videos available on its servers to its customers at any
given time, but at least on the client side of the equation, switched digital video puts all of the necessary
elements of video on demand into place.