13
October 2013
O
PEN
S
TANDARDS
cessing” software, necessarily makes use of in-
ternal processing resources. In the case of
voice transcoding, this may be a great solution
for a moderate number of simultaneous chan-
nels, however it does not scale effectively. At
upwards of 1200 simultaneous channels of
G.729 encoding, the software solution ap-
proaches 50% utilization of a typical server,
starving the original application of processing
resource. Effectively this means that additional
servers would be required to offer higher den-
sities of voice transcoding, and the cost of the
commercial software that is usually charged
on a per-channel basis soon mounts up. Al-
though it is possible to add more servers to ad-
dress this issue, accepting a reduction in ca-
pacity even for an improvement in functionality
is often difficult to manage from a product
line perspective. It results in a downgrade of
capacity within the same product offering, so
cannot really be viewed as adding functionality.
Matters get even worse when considering field
upgrades since a customer must accept that a
given installation would no longer be able to
carry the same traffic.
A more elegant solution to the problem is to
use a plug-in media processing accelerator to
offload both audio and video processing from
the server host. This keeps the function internal
to the network element and avoids the loss of
central processing resource that would other-
wise be required to run a fully software solution.
Ideally this would be able to take account of
new voice and video compression schemes as
they emerge. In this case, using a plug-in
media processing accelerator offers a true up-
grade path.
It is now possible to deploy PCI Express media
processing boards that offer high performance
voice and video transcoding based on digital
signal processing (DSP) technology. Some
boards even offer voice and video processing
Figure 1. Session border controllers are gateways between heterogeneous networks.
Figure 2. A conventional host media processing (HMP) solution can compromise server
performance.
