Browse Prior Art Database

Efficient Transport of Multimedia Data in an IP Environment

IP.com Disclosure Number: IPCOM000117130D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 131K

Publishing Venue

IBM

Related People

Kandlur, DD: AUTHOR [+2]

Abstract

Transporting multimedia data between user workstations and between subsystems within the user workstation is considered. For multimedia applications such as desktop videoconferencing it is very important to provide a low overhead, high throughput path between the video subsystem and the communications subsystem. The efficiency of this path has significant impact on the quality of the video and audio, and on the processing power available for user applications. In this disclosure we present a transport scheme that provides an efficient path between the video and communications subsystems. One of the most desirable features of this scheme is that it does not require any modifications to the existing communication subsystem (in particular, the TCP/IP protocol stack) available in user workstations.

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Efficient Transport of Multimedia Data in an IP Environment

      Transporting multimedia data between user workstations and
between subsystems within the user workstation is considered.  For
multimedia applications such as desktop videoconferencing it is very
important to provide a low overhead, high throughput path between the
video subsystem and the communications subsystem.  The efficiency of
this path has significant impact on the quality of the video and
audio, and on the processing power available for user applications.
In this disclosure we present a transport scheme that provides an
efficient path between the video and communications subsystems.  One
of the most desirable features of this scheme is that it does not
require any modifications to the existing communication subsystem (in
particular, the TCP/IP protocol stack) available in user
workstations.  There are several mechanisms possible for exchanging
data which differ widely in cost, throughput, and flexibility.  At
one end of the spectrum hardware bus connectors are between the CODEC
and the communication adapter.  This solution provides the best
throughput, with minimum impact on workstation performance.  However,
this approach also has some drawbacks that limit its use:  it
requires modifications to the communications adapter and adds cost to
the design.  This approach cannot be used with existing
communications adapters.

      At the other end of the spectrum is the application level
transfer.  This is a software-only approach in which the user
application is responsible for moving data between the CODEC and the
communications stack.  Its primary drawback is its performance:  the
data path between the communications adapter and the CODEC is long
and inefficient.  Also, since the data has to cross the user--kernel
boundary there are additional overheads incurred such as buffer
copying.  In the worst case, the outgoing data may be copied 3 times
before it is transmitted on the network.

      A more desirable mechanism for transfering data from the CODEC
system to the network is to use a ''peer to peer'' transfer between
the CODEC adapter and the network adapter.  This requires a close
cooperation  of the two adapters, and special code in the network
adapters.  It also requires a tailored communications protocol stack
to support the adapters.

      On the other hand, it is desirable to improve the efficiency of
the data transfer in a manner that is consistent with the structure
of current desktop operating systems, and can work in a wide variety
of environments such as OS/2*, DOS/Windows, etc.  This approach is
more suitable for desktop systems since it does not require any
changes to the user's environment.

      The idea here is to localize any required changes to the CODEC
software (in particular, the device driver), and to leave the host
system software unmodified.  It exploits the routing capabilities of
the IP communications st...