Image Processing Reference
In-Depth Information
This technology is designed to be deployed in mobile situations. When the mobile
camera is able to reliably “read” the human face and reduce the expression to some math-
ematical description, very low bit rates will be possible.
39.5.14
Profiles and Levels
The complexity issues have been simplified somewhat by the work done by the Internet
Streaming Media Alliance (ISMA), which has developed a series of profiles and levels
that bound the problem. The player determines what the profile is, to ascertain what
functionality it will need to invoke. The level tells it the scope and size of the data that it
must deal with.
The profiles and levels available to implementers of the MPEG-4 standard are sum-
marized in detail in Appendix G. You must be careful to code your video to a profile and
level that matches the player that you are targeting. If you don't, then the player should
display an error alert and complain that the format is unsupported. That is a best-case sce-
nario. Less compliant players may attempt to decode the stream assuming it is okay, and
they will soon run into serious difficulties.
A particularly well-implemented player might be smart enough to ignore the more
complex aspects of the video that it cannot decode. The playback would be compromised
but a usable moving image would be displayed even though it not at the highest quality.
Such players are still some way off as the MPEG-4 standard is still very new and the
licensing requirements are such that they discourage many people from taking it up at
present.
39.5.15
MPEG-4 Risk Analysis
Some risks are involved if you plan to go with MPEG-4 as part of your strategy. There
are in fact only a small number of companies that provide MPEG-4 authoring tools and
these are listed in the appendices. There are potentially many more but they need to
upgrade their existing tools to cope with the MPEG-4 content in addition to what they
already work with.
The support for BIFS will grow in due course when there are appetites for adding
identical cross-platform interactive content to the World Wide Web, DVDs, PVRs, and
broadcast TV. MPEG-4 has the potential to deliver that genuine “author once, deploy
everywhere” model.
There is a risk at present that you will be locking into a minority codec/player. The
video aspects are portable and playable across a wide variety of platforms. But the BIFS
support is still quite restricted and authoring tools for it are rare.
While there are risks associated with adopting MPEG-4, there are also risks associ-
ated with ignoring it. You may get left behind. The licensing situation is substantially
resolved and as the terms become more attractive, the take-up may well be rapid and
widespread. If you choose what looks to be an attractive alternative today and lock into
that, you may regret that decision within just 12 to 18 months. Electing to keep your
options open at this stage is a good strategy.
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