Browse Prior Art Database

Simplifying Video Application Components in Conferencing Systems

IP.com Disclosure Number: IPCOM000117613D
Original Publication Date: 1996-Apr-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Key, A: AUTHOR [+3]

Abstract

A video conferencing system includes a collection of communications mechanisms, such as network cards, with associated software Link Support Modules (LSMs). It may also include a collection of video capture and display mechanisms, such as video cards, with their associated software Video Support Modules (VSMs). Above this are assorted layers of software and applications programs, collectively called 'Conferencing System'.

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Simplifying Video Application Components in Conferencing Systems

      A video conferencing system includes a collection of
communications mechanisms, such as network cards, with associated
software Link Support Modules (LSMs).  It may also include a
collection of video capture and display mechanisms, such as video
cards, with their associated software Video Support Modules (VSMs).
Above this are assorted layers of software and applications programs,
collectively called 'Conferencing System'.

      Such a configuration might be described as a software dataflow
system because typically, the VSM supplies packets of video as memory
buffers on demand, or at regular intervals to the conferencing
system.  The conferencing system then passes these buffers to a LSM
to get the data transmitted elsewhere.

      Complexity is introduced into this simple programming model by
video cards that can display the video they capture without involving
the CPU, and cards which are both video and networking cards
combined.  In both cases, video data need never enter the computer's
memory, and no time need be spent copying data around.

      Current conferencing systems handle local display through the
use of a wider (and thus more complicated) API which introduces the
complexity of a video capture session having a display capability.
They address the combined video and network adaptor problem by the
introduction of new APIs specifically for this purpose.  According
the video application arts of the conferencing system are
considerably more complicated than they need to be.

      This complexity is avoided in the system described here by
introducing the requirement that the LSMs or networking system, and
the video LSMs, produce and accept a datatype called a 'delayed
buffer' DBUF, instead of a memory buffer.

      A DBUF is a delayed data reference.  When data addressed by a
DBUFs is accessed, the originator of the DBUF is notified.  This is
necessary for the conferencing type application.

      A DBUF is a 'promise to pay', or 'information on credit'.  It
is a small object which contains (in this sample instance) a
reference count, a cookie and three callback functions, called
inc_ref, dec_ref and get_ptr.

      In a software dataflow environment, when module A creates a
DBUF, it stores data in the cookie which points to the real data in
question.  The reference count is made 1, and the function...