Home multimedia devices will start
sporting the Digital Living Network
Alliance (DLNA) logo this year, and the
number of products adopting this standard
will likely increase. Most vendors
of multimedia hardware are members
of DLNA and have access to its standards.
The cost of joining is minimal,
and it's a requirement for getting
devices DLNA-logo certified.
Meanwhile, we can provide a little
insight into the structure and operation
of DLNA devices since they're based
upon the open Universal Plug-n-Play
(UPnP) standard. The DLNA standard
specifies the required UPnP subset
that every DLNA device must support
(see the figure).
It's possible to support more of the
UPnP standard, provide more mediaformatted
files, and still comply with
the standard. UPnP also defines a
range of devices that DLNA does not
cover, such as lighting controls. Still,
all the UPnP devices should be able to
coexist if not interact with each other
at some level.
A typical mechanism implemented on
DLNA media servers, real-time transcoding,
lets devices maintain data in a single
format but deliver it to another DLNA
device in another format. Of course, this
means the server requires enough horsepower
to handle the transcoding.
DLNA devices use the standard UPnP
discovery and control protocols to identify
new devices. Application software is still
required to handle the presentation and
control interaction, but these applications
will utilize the UPnP application programming
interface (API) standard.
The DLNA standard is likely to
expand over time to incorporate more
devices and extend the functionality
available between devices. Digital
rights management (DRM) support is
part of the standard, but you will need
to become a DLNA member to find out
the requirements.
Most UPnP stack developers also
have a DLNA variant. This will make the
job of creating a DLNA-compatible
device easier.
www.dlna.org
www.upnp.org