Image Processing Reference
In-Depth Information
During 2004, the relevant standards bodies agreed that the H.264 codec would be
ideally suited to delivering HDTV transmissions in Europe. It had already been ratified as
one of the additional codecs for use on DVD, Windows Media being another.
High-definition TV is becoming more popular and the same techniques and infra-
structures as are used for standard-definition TV are applicable. The bit rates for HDTV
are somewhat higher for uncompressed material. This is where new coding standards
such as H.264 or VC-1 facilitate the transmission of HDTV in existing SDTV networks.
Convergence with the PC
With receivers becoming essentially just PCs in brushed aluminium cases, and PCs becom-
ing more powerful all the time, good receiver-application design in the future should
allow some degree of prediction. For example, if the user is channel hopping, some sense
of what the user is doing may allow the receiver to buffer the multiplex on which it expects
the next selected channel to be located.
Simple one-tuner devices such as the El-Gato Eye TV 400, when plugged into the UK
Terrestrial Freeview service, deliver a very good viewing experience, and the technology
allows for some interesting home media server development if you connect the tuning and
recording processes to an automation system.
Broadcast Streams
Digital television services all over the world have been deploying MPEG-2 video content
embedded within a transport stream. These transport streams are specified by the MPEG-2
standard and are compatible with satellite, terrestrial, and cable systems. Indeed, it is tech-
nically possible to deliver the same transport stream to all the platforms provided that it car-
ries a superset of the necessary supporting data streams suitable for all three. This would not
be practical for public consumption but is useful in a test and prototyping environment
when researchers are developing interactive content and attempting to preview the result.
Evolving the Transport Stream
Because the MPEG-2 transport stream mechanism is sufficiently well evolved, the MPEG-
4 standard did not seek to introduce any changes. The MPEG-2 standard allows MPEG-4
content to be carried alongside the MPEG-2 streams in the existing infrastructure. This
allows new services to be developed and tested without complete replacement of the
broadcast systems that are already working, which have required a significant investment
in time and money to develop.
Organizations such as DVB govern the broadcast mechanisms and decide what may
be carried. The H.264 codec is likely to be deployed for broadcast HDTV deployment in
Europe. It may be that other standards will be deemed acceptable as well, such as SMPTE
VC-1 (based on Windows Media), if and when that is finally ratified as a standard.
However, it is looking increasingly unlikely that VC-1 will be ratified in time.
Search WWH ::

Custom Search