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We have implemented an experimental distributed multimedia system,
called the Active Multimedia System (AMS), based on the concept of transformation
among multimedia schemas and the object
exchange manager, as shown in Figure .
The system is implemented in the X-Window environment on the SUN SPARCstation 5.
The object exchange manager is written in C++ programming language, while the
other modules are written in C programming language.
On the top level of the system is an application window which provides an
integrated user interface for performing various tasks. Illustrated
in Figure is a screen dump of the application window.
The pull-down menus in the top portion of the window provide functionalities
for editing, attributes defining, playback, transformation, packing/unpacking
to/from object exchange format, transmission, etc.
When composing a multimedia object, the user can choose buttons in the left
panel of the window to create links and nodes for constructing the hypergraph
structure of the MSS.
Figure: User interface window of the AMS system.
Figure: Example of creating a composite object and invoking transformation in
the AMS system.
Figure: A screen dump of multimedia objects playback in AMS.
Figure: Another screen dump of multimedia objects playback in AMS.
Referring to the system structure shown in Figure , the steps of
a typical scenario to compose, view, send, and receive a composite
multimedia object in our system are as follows:
- Editing the hypergraph structure of the MSS:
The user can click on Add in Edit pull-down menu and buttons in
the left panel to create nodes and links for the MSS. For example, in
Figure , a composite object C0
composed of basic objects M0, M1, and M2 is created.
A temporal link
defining the temporal relation between M0, M1, and M2 is created.
A location link and an annotation link
defining the spatial relation and the annotation between M0 and another
composite object C1 are also created, respectively. This hypergraph
structure corresponds to the one shown in Figure (a). - Defining attribute:
In the pop-up dialogue box brought up by clicking on the options in the
Attr pull-down menu, the user can
define the attributes of nodes and links in the MSS,
such as media type of an object, the corresponding file name,
temporal relation defined by a temporal link, and so on. For example,
we can define in Figure the type of M0 as image and
M1 as audio as well as their
corresponding file names. For the temporal link linking M0, M1,
and M2, the temporal attribute is defined as co-begin. - Performing transformation from MSS to MDS:
After the MSS is constructed, MDS in the Gnet pull-down menu, as
shown in Figure , is
chosen to perform the transformation from MSS to MDS. - Playback:
Once the MDS is created, the user can view the presentation of the composite
multimedia objects according to the MDS by clicking on Playback in
Viewer pull-down menu. The playback by the Presentation module is based on the token flow in
the MDS. When a token flows to a place in the MDS, the corresponding object
is displayed. For example, in Figure , a text, an image,
and an audio are displayed as there are tokens in their corresponding places.
The corresponding MDS is also shown at the lower right corner of the screen.
Later on, when tokens flow to , , and
,
two more texts (``Tumor???" and ``OK here.") and one animation (the freehand
circle) are displayed as the annotation of the image
as shown in Figure .
Note that a reference window with text ``Please see reference [C2]." is shown
on the screen despite the referenced object C2 is not a part of the MDS. - Performing transformation from MDS to MCS:
By clicking on MCS in the Gnet pull-down menu (see
Figure ), the MDS is transformed into MCS. - Packing into OEF:
The user then packs objects into an OEF file by choosing Export in
the Ex_Format pull-down menu. - Sending and/or depositing multimedia objects:
The multimedia objects will be sent after the user clicks on Send in
the Transmit pull-down menu. A Deposit option is also available
in this pull-down menu for the user to store the objects in a specified
directory.
At the receiving end, the receiver can choose Receive in the
Transmit pull-down menu to retrieve the
multimedia object and the corresponding G-Net specification of the MDS from
the mailbox. The user can then playback the object according to the MDS.
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Thu Mar 27 17:33:45 EST 1997