The same service is required to register and lookup a
conference id to Multicast group mapping as for audio.
But we must also register a ;SPM_quot;callback;SPM_quot; for floor
control interactions, and we may need to register
subgroups of the video conference to allow conferees on
lower bandwidth lines to receive different samples of
the video (ref ian's hierarchical coding). Callback handlers are needed
whereever another thjread of control in a distributed system may
wish to communicate asynchronously with this one.
Workstations do not have sufficient display real estate
to view more than a small number of video scenes. In
fact, it would be distracting (and not particularly
useful since we can display more technical information
such as a document or design under discussion).
Therefore we want to have floor control interact with
the video delivery system. There are two possible
Each conferees video could be sent to a different
IP group. We could use receiver selection by
simply joining the right group(s).
Only a single or small number of conferees send
at one time (selected by floor control).
We multiplex multiple video signals on screen (or
select) based on source address.
Since a WAN can deliver more than a very small number
of end systems' video, we need intelligent multicast
routers that interact with the floor control scheme[#handley##1#].
It is not easy to see how we
could employ any obvious form of ;SPM_quot;video silence
suppression;SPM_quot; any more than the common video compression
algorithms already do.