ISO/IEC TR 15938-8:2002/Amd 2:2006
(Amendment)Information technology — Multimedia content description interface — Part 8: Extraction and use of MPEG-7 descriptions — Amendment 2: Extraction and use of MPEG-7 perceptual 3D shape descriptor
Information technology — Multimedia content description interface — Part 8: Extraction and use of MPEG-7 descriptions — Amendment 2: Extraction and use of MPEG-7 perceptual 3D shape descriptor
Technologies de l'information — Interface de description du contenu multimédia — Partie 8: Extraction et utilisation des descriptions MPEG-7 — Amendement 2: Extraction et emploi du descripteur de forme 3D perceptuel MPEG-7
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TECHNICAL ISO/IEC
REPORT TR
15938-8
First edition
2002-12-15
AMENDMENT 2
2006-12-01
Information technology — Multimedia
content description interface —
Part 8:
Extraction and use of MPEG-7
descriptions
AMENDMENT 2: Extraction and use of
MPEG-7 perceptual 3D shape descriptor
Technologies de l'information — Interface de description du contenu
multimédia —
Partie 8: Extraction et utilisation des descriptions MPEG-7
AMENDEMENT 2: Extraction et emploi du descripteur de forme 3D
perceptuel MPEG-7
Reference number
ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
©
ISO/IEC 2006
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ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
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ii © ISO/IEC 2006 – All rights reserved
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ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
In exceptional circumstances, the joint technical committee may propose the publication of a Technical Report
of one of the following types:
— type 1, when the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts;
— type 2, when the subject is still under technical development or where for any other reason there is the
future but not immediate possibility of an agreement on an International Standard;
— type 3, when the joint technical committee has collected data of a different kind from that which is
normally published as an International Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether
they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to
be reviewed until the data they provide are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 2 to ISO/IEC TR 15938-8:2002 was prepared by Joint Technical Committee ISO/IEC JTC 1,
Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia
information.
NOTE This document preserves the sectioning of ISO/IEC TR 15938-8:2002 and its amendments. The text and
figures given below are currently being considered as additions and/or modifications to those corresponding sections in
ISO/IEC TR 15938-8:2002 and its amendments.
© ISO/IEC 2006 – All rights reserved iii
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ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
Information technology — Multimedia content description
interface —
Part 8:
Extraction and use of MPEG-7 descriptions
AMENDMENT 2: Extraction and use of MPEG-7 perceptual 3D
shape descriptor
Add after 2.2.2.49:
2.2.2.50 Attributed Relational Graph (ARG)
A graph whose nodes (vertices) and edges (links) contain unary attributes and dyadic attributes (describing
the relation between the nodes), respectively. The graph is described in the form of a vector.
2.2.2.51 Constrained Morphological Decomposition (CMD)
An algorithm, based on the mathematical concepts of morphology and convexity, to decompose a voxelized 3-D
object into several parts.
2.2.2.52 Weighted Convexity (WC)
A volume-weighted sum of each part's convexity.
2.2.2.53 Weighted Convexity Difference (WCD)
A difference of two WCs before and after merging of two parts.
2.2.2.54 Initial Decomposition Stage (IDS)
The procedure of applying the CMD to a voxelized 3-D object, once.
2.2.2.55 Recursive Decomposition Stage (RDS)
The procedure of applying the CMD recursively to the result of the IDS or a previous RDS.
2.2.2.56 Iterative Merging Stage (IMS)
The procedure of merging parts in the result of the RDS iteratively using the WCD.
2.2.2.57 Earth Mover’s Distance (EMD)
A kind of distance measure based on a solution [AMD2-2] to the transportation problem in graph theory.
© ISO/IEC 2006 – All rights reserved 1
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ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
2.2.2.58 Query by Example
A query to a content (e.g. image, 3D object, etc.) retrieval system whereby the information need is expressed
visually, by providing an example of the kind of target content desired. This can be useful when the user has
difficulty forming a query using key words or when text descriptions are not present in the database. For
example if the user wants to find images of beaches, he/she can use any available image of a beach as the
query and the retrieval system is expected to return images of beaches as results.
2.2.2.59 Query by Sketch
A query by example whereby the example content is a sketch, drawn by the user, reflecting the key visual
attributes of the information need.
2.2.2.60 Query by Modified Example
A query by example whereby the example content is created by modifying an existing example (for example,
using a graphical editing tool) so that it best expresses the information need.
Add after subclause 8.5:
8.6 Perceptual 3D shape
The Perceptual 3D Shape descriptor is a part-based representation of a 3D object expressed as a graph. In
this context “node” is a vertex in the graph representation corresponding to a part in the 3D model. Such a
representation facilitates object description consistent with human perception. The Perceptual 3D Shape
descriptor supports ‘Query by example’. Furthermore, it provides unique functionalities, such as ‘Query by
sketch’ and ‘Query by modified example’, which make the content-based retrieval system more interactive and
intuitive in querying and retrieving similar 3D objects.
8.6.1 Part-based representation
Part-based representation of 3D objects enables perceptual recognition that is robust in the presence of
rotation, translation, deformation, deletion, and inhomogeneous scaling of a 3D object. More specifically,
deletion and inhomogeneous scaling involve the removal of parts and growth or shrinkage of the specific part,
respectively. In the task of forming a high-level object representation from low-level object features, parts
serve as an intermediate representation.
The decomposition scheme [AMD2-1] is used to generate the attributed relational graph (ARG) of a 3D object.
The proposed scheme recursively performs the constrained morphological decomposition (CMD) based on
the mathematical morphology and weighted convexity. Then, a merging criterion based on the weighted
convexity difference (WCD), which determines whether connected parts should be merged or not, is adopted
for compact graph representation. The block diagram of the proposed scheme, in terms of three stages, is
presented in Figure AMD2-1. The recursive decomposition stage (RDS) will be launched after the initial
decomposition stage (IDS) and performed until QUEUE I is empty. Then, the iterative merging stage (IMS) is
applied to parts in QUEUE II for the compact graph representation. Figure AMD2-2 shows the procedure of
the proposed scheme for a ‘cow’ step by step. Figure AMD2-2 (a) and (b) show the ‘cow’ represented by
rendered meshes and voxels, respectively. Then, Figure AMD2-2 (c), (d), and (e) show results of IDS, RDS,
and IMS, respectively. Finally, the simple ARG representation is presented in Figure AMD2-2 (f), where the
ellipsoidal node and edge represent the corresponding part and connectivity between parts, respectively.
2 © ISO/IEC 2006 – All rights reserved
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ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
IDS: Initial Decomposition Stage
Constrained
Voxelized
Queue I
morphological
3-D Object
decomposition
RDS: Recursive Decomposition Stage
No
Queue I Is this part
Queue II
to be split?
Yes
Constrained
morphological
decomposition
IMS: Iterative Merging Stage
Merging procedure
Queue II
with the
ARG representation
merging criterion
Figure AMD2-1 — The block diagram of the decomposition scheme
(a) (b) (c)
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ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
(d) (e) (f)
Figure AMD2-2 — The procedure of generating a part-based representation
8.6.2 Feature extraction
As described in the previous subclause, the Perceptual 3D Shape descriptor has the form of an ARG,
composed of nodes and edges. A node represents a meaningful part of the model with unary attributes, while
an edge implies binary relations between nodes. In order to obtain all attributes, principal component analysis
(PCA) is performed on every part of the 3D model to find three principle axes, where the 1st principal axis
corresponds to the principal direction with biggest variance, and the 3rd axis corresponds to the direction with
smallest variance. Afterwards,, 4 unary attributes and 3 binary relations are extracted to form a Perceptual 3D
Shape descriptor. In detail, a node is parameterized by volume v, convexity c, and two eccentricity values e
1
and e . More specifically, the convexity is defined as the ratio of the volume in a node to that in its convex hull,
2
2 2 2 2
e= 1−c /a e = 1−c /b
1 2
and the eccentricity is composed of two coefficients, and , where a, b, and c (a ≥ b ≥
c) are the maximum ranges along 1st, 2nd, and 3rd principal axes, respectively. Then edge attributes, i.e.
binary relations between two nodes, are extracted from the geometric relation between two nodes, in which
the distance between centers of connected nodes and two angles are adopted. The first angle is the angle
between the 1st principal axes of the connected nodes and the other is between their 2nd principal axes. All
the unary attributes and binary relations are normalized into the interval [0, 1]. However, to adopt ‘Query by
sketch’ in the retrieval system, the Perceptual 3D Shape descriptor is required to be represented by the set of
ellipsoids. In this context, each ellipsoid contains three properties, such as Volume, Max (i.e. maximum range
along each principle axes) and Convexity, which can easily be converted into the 4 unary attributes. Next, the
Perceptual 3D Shape descriptor contains three properties, such as Center, PCA_Axis_1 and PCA_Axis_2 (i.e.
1st and 2nd principle axis) from which the 3 binary relations can be computed. Therefore, an actual
Perceptual 3D Shape descriptor is created, as shown in Binary Representation Syntax. Note that Volume,
Center, Max and Convexity are in the interval [0, 1], while the components in PCA_Axis
...
TECHNICAL ISO/IEC
REPORT TR
15938-8
First edition
2002-12-15
AMENDMENT 2
2006-12-01
Information technology — Multimedia
content description interface —
Part 8:
Extraction and use of MPEG-7
descriptions
AMENDMENT 2: Extraction and use of
MPEG-7 perceptual 3D shape descriptor
Technologies de l'information — Interface de description du contenu
multimédia —
Partie 8: Extraction et utilisation des descriptions MPEG-7
AMENDEMENT 2: Extraction et emploi du descripteur de forme 3D
perceptuel MPEG-7
Reference number
ISO/IEC TR 15938-8:2002/ Amd.2:2006(E)
©
ISO/IEC 2006
---------------------- Page: 1 ----------------------
ISO/IEC TR 15938-8:2002/Amd.2:2006(E)
PDF disclaimer
PDF files may contain embedded typefaces. In accordance with Adobe's licensing policy, such files may be printed or viewed but shall
not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading a PDF file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create the PDF file(s) constituting this document can be found in the General Info relative to
the file(s); the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the files are suitable for
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address given below.
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