Monday, October 17, 2011

Scalable Video Coding

SVC (Scalable Video Coding) is an extension to the H.264 codec standard that is used by most of video conferencing devices. SVC video technology allows video conferencing devices to send and receive multi-layered video streams composed of a small base layer and optional additional layers that enhance resolution, frame rate and quality of video transmit.

Scalable Video Coding Benefits

Scalable Video Coding allows applications to send a single
video stream, encoded only once, but able to support a
range of resolutions, bitrates and quality levels, via the
process of discarding selected data (“layer thinning”).
This means that clients with limited resources (display
resolution, processing power, battery, etc.) can decode
a subset of the original stream, which best suits their
capabilities.

Note that layer thinning can be done not only by the
receiving client, but also by any Media-Aware Network
Element (MANE) in the system. Therefore, in multi-cast
scenarios, terminals with different network conditions
can be served by a single scalable bit stream.
As the transmitted stream is encapsulating different
sub-streams representing different possible streams, the
need for transcoding, as a means to adapting content to
meet recipient capabilities is eliminated.

Scalable Video Coding Applications

More and more applications are using the public Internet
as their main means of transport. Among these are hosted
services (“in the cloud”), consumer applications and global
corporate networks, which rely on the public internet
for inter-branch connectivity.
Error resiliency, therefore, becomes one of the biggest
challenges for mass deployment of visual communications
infrastructure, and a constant obstacle preventing a high
quality experience.
Furthermore, in some cases the video transmission is not
point-to-point, but point-to-multipoint (i.e. streaming) or
multipoint (i.e. video conferencing). Therefore, the need
for stream scalability becomes a key factor in application
feasibility and success.
SVC offers great value to most video-based applications
in exactly these two areas: error resiliency (through
mainly temporal scalability) and high scalability (through
spatial and quality scalability).
One may argue that scalability always comes with a cost
and that in some cases scalability is not beneficial (and
in fact, may reduce the quality of experience). However,
used wisely and in the right configuration, scalability
brings benefit to almost any use-case.
For example, in a point-to-point video call spatial
scalability or quality scalability might not be effective,
and the bit rate penalty may reduce the overall quality.
However, temporal scalability can offer error resiliency
even in a point-to-point scenario.
As any application that involves the transmission of a
video stream to one or more recipients can achieve a
significant gain from scalable video coding, application
areas relevant for scalable video coding include: Point-topoint
video calling, video conferencing, video streaming,
and more.


source : www.radvision.com

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