MPEG-4 Development at the CSIRO / DCS Virtual Environments Laboratory
Introduction
MPEG-4 is an
ISO and IEC standard for the
communication of interactive multimedia scenes.
The original goal of MPEG-4 was very low bit-rate coding of video, and
has since been modified to generic coding of audio-visual objects for
multimedia applications.
The standard
specifies coded representations for natural or synthetic, two or three
dimensional, audio-visual objects, along with their spatio-temporal
positioning and response to user interaction. See
Julien Signes' article
for futher information on MPEG-4 and its scene description language.
The object-based nature of MPEG-4 has led to new challenges in
delivery mechanisms, where large numbers of streams, each representing
an object or object heirarchy, have to be
handled, multiplexed and synchronized.
The members of ISO and EC who are contributing to the standard from a
consortium who meet regularly to discuss open issues and make
decisions on the content of the standard. Consortium members contribute
software that implements the standard for the purpose of
conformance testing and performance analysis, as well as a number of
scene authoring tools. The contribution of the
VE Lab involves
enhancing the
consortiums MPEG-4 player / renderer, called Player3D,
and producing interactive content
from haptic and collaborative VE applications. This software is freely
available to consortium members.
The Multimedia Content Delivery Integration Framework
MPEG-4 supports three main media delivery technologies, namely; broadcast
(cable, satellite etc), storage (CD, DVD etc) and interactive network
mechanisms. The interface to these mechanisms is the Delivery
Multimedia Interface (DMIF). While the broadcast and storage mechanisms have been
defined in versions 1 and 2 of the standard, the interactive network
delivery mechanism is still under discussion, and will be finalized in
version 3 by December 2000.
The Virtual Environments Laboratory and MPEG-4
The
Virtual Environments
laboratory at the Australian National
University is the result of a research program run jointly by the
CSIRO Mathematical and Information Sciences department (CMIS), and the
Department of Computer Science at ANU. Two of the projects which make
up the VE program are Collaborative VE (COVE), and Haptic Workbench
Software (HWS) development. These two projects have utilised MPEG-4
as the main communications and delivery mechanisms in their
demonstrators.
The haptics demonstrator is a virtual sculpt application, where the
user can use a sculpting tool to touch and feel a virtual piece of
clay, and effect transformations on the clay's shape and colour. The
application has been extended to act as an MPEG-4 sending terminal,
and can accept connections from an MPEG-4 client and subsequently
stream the clay object and its tranformations to the client. The
client is a modified Player3D that has an added module,
developed by the VE lab, that implements the DMIF for interactive
network delivery. The client player accepts a url for the sculpt
server and makes the connection and displays the sculpting activity.
A video of this demo is
here
Prepared by David
Walsh, at the Virtual
Environments Laboratory.
Last modified: Fri Apr 20 13:23:17 EST 2001