Image Processing Reference
In-Depth Information
Confusingly, MHEG is named similarly to the MPEG standard but is an altogether
different thing. MPEG describes video in a compact and coded form; MHEG describes
interactivity in an object-based scene structure. There are similarities between MHEG
and MPEG-4 part 1 multimedia, but MPEG-4 is far more sophisticated in what it
offers.
27.1.3
Digital Cable TV
The same DVB-based MPEG-2 transport stream model as DSat and DTT is used for digi-
tal cable TV (DCable) services in the United Kingdom. The interactivity is implemented
using a variant of HTML that was developed by Liberate. DCable TV is delivered though
a network of copper cables connected through a series of distribution amplifiers direct to
your house. Cable operators also provide telephone connections and Internet services.
This is sometimes called a “triple play.” With suitable head-end infrastructures, they are
also rolling out video-on-demand services. This method has the highest chance of being
superseded by broadband connectivity.
27.1.4
Broadband TV
Broadband delivered via the telephone service provider is gradually being investigated as
a possible way to distribute broadcast TV signals. This is sometimes called IPTV (after the
Internet Protocol, which is the basis of its delivery) or video on demand (VOD). The
strengths of broadband-based TV solutions are in the area of unicasting rather than mul-
ticasting. The main limiting factor of broadband is the last mile of connectivity, which is
most often provided by legacy copper wiring. Signal attenuation affects the reliability and
integrity of the data stream. Some broadband suppliers guarantee availability only up to
a limited distance away from an optical-fiber transducer.
27.1.5
Hybrid Services
Combining digital satellite or digital terrestrial broadcasting with broadband for auxiliary
services provides the optimal service. Combining broadband with DCable would seem to
be redundant, since you would be putting in twice as many wires as necessary. If you are
going to the trouble of wiring at all, then why not put in high capacity with a return path
on the same connectivity?
27.1.6
Multimedia Home Platform
European digital TV services are being prepared and launched on a multimedia home
platform (MHP)-based platform. This is being made available in the same way across the
different kinds of transmission, so the receivers are very similar, as are the opportunities
for adding interactivity.
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