Image Processing Reference
In-Depth Information
27
Digital Television
27.1
Digital TV Broadcasting
This is probably the most common way that compressed video is delivered, at least
when measured by the number of receivers being viewed by end users. The main benefit
of broadcasting is that although just one copy is transmitted, everybody can see it by
receiving it on an aerial antenna and then decoding it into a form that can be viewed on a
TV set.
The UK digital TV industry has rolled out three fundamentally different platforms,
and a fourth is rapidly gaining acceptance.
27.1.1
Digital Satellite TV
Digital satellite (DSat) services in the United Kingdom are based on MPEG-2-coded video
contained within MPEG-2 transport streams and some additional support for Open TV-
coded interactivity. The DSat services are delivered to a dish antenna mounted on the roof
or exterior wall of your dwelling.
The Digital Video Broadcast (DVB) Organization has looked again at the specifica-
tions for the DSat delivery protocols and evolved a second-generation approach. The
DVB-S2 transmission techniques are 30% more efficient than the previous DVB-S delivery
protocols. This, coupled with the improvements in coding offered by H.264, means that
HDTV delivery is now a realistic proposition.
27.1.2
Digital Terrestrial TV
Digital terrestrial TV (DTT) broadcasting in the United Kingdom uses a DVB-based pack-
aging technique very similar to the satellite service. A transport stream carries the pro-
grams and other data in the same way but deploys interactivity with the MHEG standard.
The DTT broadcast uses the same spectrum as analog TV but simply uses some of the
channels in a more efficient way.
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