Pulse or digital communications – Bandwidth reduction or expansion
Reexamination Certificate
1999-10-06
2002-04-30
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Reexamination Certificate
active
06381273
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to the representation of the spatial and temporal information of an audio-visual scene. In object-based compression of a scene, where the individual objects that form the complete scene are compressed separately, a means of representing the spatial and temporal relationship of the objects is necessary. In a typical scene, it is possible that the properties of one object are used to affect the properties of another. This invention is essential for representing and recreating a scene by facilitating exchanges of properties between two objects.
2. Description of the Related Art
MPEG-4 [1] specifies an object-based compression of digital audio-visual information. It allows object-based interactivity of multimedia content by delineating the audio-visual objects of the scene and separately compressing each of them. The compressed audio-visual data is augmented with a scene description that is used by the decoder to reconstruct the scene by compositing the individual audio-visual objects at the decoder. In MPEG-4, the scene description is referred to as binary format for scene description (BIFS).
The scene description data is in the form of a scene tree made up of nodes and routes as shown in FIG.
1
. An audio-visual object is represented by a collection of nodes. Nodes contain information or properties of the object. Routes are used to link the properties of the nodes such that the properties of one object can be used to affect the properties of another object.
According to the prior art, some form of data type casting is essential to the usefulness and success of the BIFS. This is because by definition the values at the two ends of a route must be of the same data type. Currently, the valuator can be used for this purpose, as shown in FIG.
2
. Data from field
1
of node
1
is routed through the valuator node to field
1
of node
2
. However, due to the static nature of the valuator, the second node will always receive a fixed value regardless of the first node. As such, the value of field
1
of node
2
cannot change in respond to field
1
of node
1
. However, this gives rise to other problems which will be discussed in the next section.
In the VRML specification [2], the second prior art, scripting is usually used to provide this data type casting mechanism. However, scripting is more complex and requires that the users learn the scripting language. Furthermore, implementation of a scripting node requires an interpreter that has much higher resource requirements.
In the Systems Final Committee Draft (document ISO/IEC JTC1/SC29/WG11 N2201) [1], the valuator node is defined for allowing output values of a node to be routed to an input value of another node of different data type. For example, an output value of data type Boolean (TRUE/FALSE) can be connected to an input value of floating-point data type by using the valuator node. However, the MPEG System Committee Draft defines the output of the valuator node to be a constant, this severely limits the use of the valuator node for type casting purposes resulting in extreme difficulties in creating a more complex scene. In fact, many valuator nodes and work-around are required to implement even simple scenes.
The current prior art have the following deficiencies:
(1) The data type of the property that is being connected from one node to another node through the route must be the same.
(2) Type casting can only be performed by a specific node called the valuator node.
(3) The output of the valuator node is always a constant.
This creates several problems especially when we would like the property of one node to influence the property of another node when the properties have different data types.
First, since route has no capability of changing the data type of the properties, properties of different data types cannot be connected. The trivial solution of course is to allow routes to handle data type casting. However, this would add additional complexity to the implementation of routes, as in the majority of cases, no data type casting is necessary.
Therefore, the valuator node is necessary in order to perform the data type casting function. However, the valuator has another limitation. Its output is a constant and cannot change. Therefore, in order for the property of one node to influence the property of another node, multiple valuators are needed.
With the limitations highlighted above, it is not possible to route from the same field of nodes through two valuators, each having different constant values, as illustrated in FIG.
3
. As the last route will overwrite all information of the previous routes. However, this situation is actually quite common. In this prior art, an attempt is made to change the input field of Node
1
,
308
, depending on the output field of Node
1
,
301
. The output field of Node
1
is connected to the valuator
1
,
304
, via the route,
302
. The output of the Valuator
1
is then connected to the input field of Node
2
via route,
306
. Similarly, the same output of Node
1
is also connected to valuator
2
,
305
, via the route,
303
. The output of the valuator
2
is then connected to the input field of Node
2
via route,
307
. However this does not create the desired result because the second route,
307
, will always overwrite the value of the first route,
306
.
The conclusion is that it is not possible to have value of input property of node
2
to dependent on output property of node
1
if they are of different data types. A means to overcome this is essential as many situation requires such type casting functionality such as a 2-state button (refer to example 1 for illustration).
SUMMARY OF THE INVENTION
Our solution to the problem is to extend and enhance the functionality of the valuator node specified in the MPEG-4 System Committee Draft by removing the constraint that the output values of the valuator node be a constant. Instead, the output values should be a function of the input values. This is illustrated in FIG.
4
. The field of the Node
1
,
401
, is connected to the input field of the valuator node,
403
, via the route,
402
. The valuator node then converts the input field to the output field by a conversion routine followed by a data type casting routine. The output field is then connected to the input field of Node
2
,
405
, via the route,
404
.
By this, we eliminate the need for multiple valuator nodes to be connected to the same destination field.
A detailed block diagram of the invention is shown in FIG.
5
. To illustrate this invention, a simple linear function of the form shown below is proposed.
f
(
x
)=factor*
x
+offset (1)
Where
factor=user specified values, one of the exposedField factor values shown in the semantic tables for the valuator below
offset=a constant value, one of the exposedField offset values shown in the semantic tables for the valuator below.
The Factor parameter allows scaling of the input values. For example, an integer value can be scaled to a value between 0 and 1 of a floating-point value by specifying 2
32
as the factor.
The offset parameter introduces an offset to the input value. This can be used to perform a delay to a certain action when used with a TimeSensor node. This value is the same as that specified in the original valuator node. Note that this is an extension to the original valuator node as most of the original functionality is preserved by setting the value of factor to be zero and offset to the required output value. This will make this new version of the valuator acts like the currently specified valuator node.
According to the first aspect of the present invention, a method for linking information of different data types in a representation of the spatial and temporal description of a scene where the spatial and temporal relationship of the objects in the scene are represented by a scene tree description comprising of a plurality of nodes which describe the propertie
Law Chee Yong
Tan Thiow Keng
Greenblum & Bernstein P.L.C.
Kelley Chris
Vo Tung
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