ISO/IEC 23001-4:2009
(Main)Information technology — MPEG systems technologies — Part 4: Codec configuration representation
Information technology — MPEG systems technologies — Part 4: Codec configuration representation
ISO/IEC 23001-4:2009 defines the methods and general principles capable of describing codec configurations in the so-called reconfigurable video-coding (RVC) framework. It primarily addresses reconfigurable video aspects and will only focus on the description of representation for video codec configurations within the RVC framework. Within the scope of RVC framework, two languages, namely FNL and RVC-BSDL, are specified normatively. FNL is a language that describes the FND, also known as “network of FUs”. RVC-BSDL is a pertinent subset of BSDL defined in ISO/IEC 23001-5. This RVC-BSDL also includes possibilities for further extensions, which are necessary to provide complete description of video bitstreams.
Technologies de l'information — Technologies des systèmes MPEG — Partie 4: Représentation de configuration codec
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 23001-4
First edition
2009-12-15
Information technology — MPEG systems
technologies —
Part 4:
Codec configuration representation
Technologies de l'information — Technologies des systèmes MPEG —
Partie 4: Représentation de configuration codec
Reference number
ISO/IEC 23001-4:2009(E)
©
ISO 2009
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ISO/IEC 23001-4:2009(E)
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ISO/IEC 23001-4:2009(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Functional unit network description .3
5 Bitstream syntax description .5
6 Model instantiation.5
Annex A (normative) Functional unit network description .7
Annex B (informative) Examples of FU network description .13
Annex C (normative) Specification of RVC-BSDL .15
Annex D (normative) Specification of RVC-CAL language.29
Annex E (informative) Instantiation of bitstream syntax parser from bitstream syntax descriptions.53
Annex F (informative) Relation between codec configuration representation and multimedia
middleware (M3W).58
Bibliography.59
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ISO/IEC 23001-4:2009(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.
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.
ISO/IEC 23001-4 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 23001 consists of the following parts, under the general title Information technology — MPEG
systems technologies:
⎯ Part 1: Binary MPEG format for XML
⎯ Part 2: Fragment request units
⎯ Part 3: XML IPMP messages
⎯ Part 4: Codec configuration representation
⎯ Part 5: Bitstream Syntax Description Language (BSDL)
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ISO/IEC 23001-4:2009(E)
Introduction
This part of ISO/IEC 23001 defines the methods capable of describing codec configurations in the so-called
reconfigurable video-coding (RVC) framework. The objective of RVC is to offer a framework that is capable of
configuring and specifying video codecs as a collection of “higher level” modules by using video coding tools.
The video coding tools are defined in video tool libraries. This part of ISO/IEC 23001 defines the MPEG video
tool library. The RVC framework principle could also support non-MPEG tool libraries, provided that their
developers have taken care to obey the appropriate rules of operation.
For the purpose of framework deployment, an appropriate description is needed to describe configurations of
decoders composed of or instantiated from a subset of video tools from either one or more libraries. As
illustrated in Figure 1, the configuration information consists of
⎯ bitstream syntax description, and
⎯ network of functional units (FUs) description (also referred to as the decoder configuration)
that together constitute the entire decoder description (DD).
Bitstreams of existing MPEG standards are specified by specific syntax structures and decoders are
composed of various coding tools. Therefore, RVC includes support for bitstream syntax descriptions as well
as video coding tools. As depicted in Figure 1, a typical RVC decoder requires two types of information,
namely the decoder description and the encoded media (e.g. video bitstreams) data.
1. Bitstream syntax
2. Decoder configuration
Decoder Description
Encoder Decoder
Encoded Video Data
Figure 1 — Conceptual diagram of RVC
Figure 2 illustrates a more detailed description of the RVC decoder.
A more detailed description of the RVC decoder is shown in Figure 2. As shown in Figure 2, the decoder
description is required for the configuration of a RVC decoder. The Bitstream Syntax Description (BSD) and
FU Network Description (FND) (which compose the Decoder Description) are used to configure or compose
an abstract decoder model (ADM) which is instantiated through the selection of FUs from tool libraries
optionally with proper parameter assignment. Such ADM constitutes the behavioral reference model used in
setting up a decoding solution under the RVC framework. The process of yielding a decoding solution may
vary depending on the technologies used for the desired implementations. Examples of the instantiation of an
abstract decoder model and generation of proprietary decoding solutions are given in Annex E.
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ISO/IEC 23001-4:2009(E)
Figure 2 — Graphical representation of the instantiation process or decoder composition mechanism
for the RVC normative ADM and for the non-normative proprietary compliant decoder implementation.
Within the RVC framework, the decoder description describes a particular decoder configuration and consists
of the FND and the BSD. The FND describes the connectivity of the network of FUs used to form a decoder
whereas the parsing process for the bitstream syntax is implicitly described by the BSD. These two
descriptions are specified using two standard XML-based languages or dialects:
⎯ Functional Unit Network Language (FNL) is a language that describes the FND, known also as “network
of FUs”. The FNL specified normatively within the scope of the RVC framework is provided in this part of
ISO/IEC 23001;
⎯ Bitstream Syntax Description Language (BSDL), standardized in ISO/IEC 23001-5 (MPEG-B Part 5),
describes the bitstream syntax and the parsing rules. A pertinent subset of this BSDL named RVC-BSDL
is defined within the scope of the current RVC framework. This RVC-BSDL also includes possibilities for
further extensions, which are necessary to provide complete description of video bitstreams. RVC-BSDL
specified normatively within the scope of the RVC framework is provided in this part of ISO/IEC 23001.
The decoder configuration specified using FNL, together with the specification of the bitstream syntax using
RVC-BSDL fully specifies the ADM and provides an “executable” model of the RVC decoder description.
The instantiated ADM includes the information about the selected FUs and how they should be connected. As
already mentioned, the FND with the network connection information is expressed by using FNL. Furthermore,
the RVC framework specifies and uses a dataflow-oriented language called RVC-CAL for describing FUs'
behavior. The normative specification of RVC-CAL is provided in this part of ISO/IEC 23001. The ADM is the
behavioral model that should be referred to in order to implement any RVC conformant decoder. Any RVC
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ISO/IEC 23001-4:2009(E)
compliant decoding solution/implementation can be achieved by using proprietary non-normative tools and
mechanisms that yield decoders that behave equivalent to the RVC ADM.
The decoder description, the MPEG tool library, and the associated instantiation of an ADM are normative.
More precisely, the ADM is intended to be normative in terms of a behavioral model. In other words what is
normative is the input/output behavior of the complete ADM as well as the input/output behavior of all the FUs
that are included in the ADM.
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INTERNATIONAL STANDARD ISO/IEC 23001-4:2009(E)
Information technology — MPEG systems technologies —
Part 4:
Codec configuration representation
1 Scope
This part of ISO/IEC 23001 defines the methods and general principles capable of describing codec
configurations in the so-called reconfigurable video-coding (RVC) framework. It primarily addresses
reconfigurable video aspects and will only focus on the description of representation for video codec
configurations within the RVC framework.
Within the scope of RVC framework, two languages, namely FNL and RVC-BSDL, are specified normatively.
FNL is a language that describes the FND, also known as “network of FUs”. RVC-BSDL is a pertinent subset
of BSDL defined in ISO/IEC 23001-5. This RVC-BSDL also includes possibilities for further extensions, which
are necessary to provide complete description of video bitstreams.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document, including any amendments, applies.
ISO/IEC 14496-2:2004, Information technology — Coding of audio-visual objects — Part 2: Visual
ISO/IEC 23001-5:2008, Information technology — MPEG systems technologies — Part 5: Bitstream Syntax
Description Language (BSDL)
ISO/IEC 23002-4, Information technology — MPEG video technologies — Part 4: Video tool library
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
abstract decoder model
ADM
conceptual model of the instantiation of the FUs (3.8) from the video tool libraries (3.16) and their
connection according to the FND (3.9)
3.2
BSD
bitstream syntax description
description containing the bitstream syntax, its implicit parsing rules, and possibly tables [e.g. VLD tables if not
already existing in the RVC (3.13) toolbox library] to define parser FU (3.8)
NOTE The BSD is expressed using RVC-BSDL (3.14).
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3.3
BSDL
description of the bitstream syntax and the parsing rules
NOTE Bitstream Syntax Description Language (BSDL) is standardized by ISO/IEC 23001-5.
3.4
connection
link from an output port to an input port of an FU (3.8) that enables token exchange between FUs
3.5
decoder configuration
conceptual configuration of a decoding solution
NOTE 1 Using the MPEG VTL (3.12), decoder configuration can be designed as one of the following cases.
⎯ A decoding solution of an existing MPEG standard at a specific profile and level.
⎯ A new decoding solution built from tools of an existing MPEG standard.
⎯ A new decoding solution built from tools of an existing MPEG standard and some new MPEG tools included in the
MPEG video tool library.
⎯ A new decoding solution that is composed of new MPEG tools included in the MPEG video tool library.
NOTE 2 In summary, an RVC decoder description essentially consists of a list of FUs (3.8) and of the specification of
the FU connections [FND (3.9) expressed in FNL (3.10)] plus the implicit specification of the parser in terms of bitstream
syntax description [BSPD expressed in RVC-BSDL (3.14)]. In order to be a complete behavioral model [i.e. ADM (3.1)] an
RVC decoder description (3.6) needs to make reference to the behavior of each FU that is provided in terms of I/O
behavior by the RVC video toolbox library specified in RVC-CAL.RVC.
3.6
decoder description
DD
description of a particular decoder configuration, which consists of two parts; FU network description (3.9)
and bitstream syntax description (3.2)
3.7
decoding solution
implementation of the ADM (3.1)
3.8
FU
functional unit
modular tool which consists of a processing unit characterized by the input/output behavior
3.9
FND
FU network description
FU (3.8) connections used in forming a decoder which are modeled using FNL (3.10)
3.10
FNL
FU network language
language that describes the FND (3.9), known also as “network of FUs”
3.11
model instantiation
building of the abstract decoder model (3.1) from the decoder description (3.6) [consisting of the BSD (3.2)
and the FND (3.9)] and from FUs (3.8) from the VTL (3.16)
NOTE During the model instantiation, the parser FU is reconfigured according to the BSD or loaded from VTL.
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ISO/IEC 23001-4:2009(E)
3.12
MPEG video tool library
MPEG VTL
video tool library (3.16) that contains FUs (3.8) defined by MPEG (i.e. drawn from existing MPEG
International Standards)
3.13
RVC
reconfigurable video coding
framework defined by MPEG to promote coding standards at tool-level while maintaining interoperability
between solutions from different implementers
3.14
RVC-BSDL
pertinent subset of BSDL (3.3), which is defined within the scope of the current RVC (3.13) framework
3.15
token
data entity exchanged between input and output among FUs (3.8)
3.16
VTL
video tool library
collection of FUs (3.8)
4 Functional unit network description
4.1 Introduction
The FUs in MPEG RVC are specified by:
• The textual description in ISO/IEC 23002-4.
• The RVC-CAL reference software. RVC-CAL is formally specified in Annex D.
The Functional Unit Network Language (FNL) is formally specified in this Clause and is used to describe
networks of FUs. FNL is derived from Extensible Markup Language (XML) which was in turn derived from
SGML (ISO 8879). The ADM consists of a number of FUs with input and output ports, and the connections
between those ports. In addition, the ADM may have input and output ports, which may be connected to the
ports of FUs or to each other.
A decoder can be described as a network of one or more FUs even when there is only one FU in the decoder
(e.g. Figure 3).
Decoder
YUV
Bits
A B
FU A
Figure 3 — FU Network of an FU
A network of FUs is described in FND. A FND includes the list of the selected FUs to form the decoder and
the three types of connections that are connections between FUs (type A), connections between decoder
inputs and FU inputs (type B), and connections between FU outputs and decoder outputs (type C), which is
illustrated in Figure 4.
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ISO/IEC 23001-4:2009(E)
The list of the selected FUs (Figure 4) is described in FND according to the following table. When selecting
FUs from VTL, the ID and name of FUs are used in the FND. The ID and name of the FUs are specified in
ISO/IEC 23002-4. The parameter assignment in the listed FU is supported in the FND, but optional.
The connections (type A, type B, and type C of Fig. B) are described in FND as shown in the following table.
Type A
Type B
Type C
Decoder
YUV
Bit s
B D
A F
FU B
FU A
C E
Type A
Type B
Type C
Figure 4 — Three types of connection in an FU network
Another example of FU network with four FUs is illustrated in the Figure 5. The textual description of Figure 5
in FND is described as follows.
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ISO/IEC 23001-4:2009(E)
Decoder
E
FU A
H
F
O YUV
Bits
B
P FU C R
Syntax
A
C
Q
Parser
D
L
K FU B
M
Figure 5 — Another example of FU network
4.2 The specification of a network of FUs
The XML structures with names of elements, such as Decl, Network, Package, Expr, etc. are described in
Annex A. In addition, attributes that direct an individual element’s features are also introduced. Attribute
names will be prefixed with “@”. For instance common attribute names are @id, @name, or @kind. In cases
where an element name may be qualified by the value of an attribute, square brackets are used. For instance,
in order to express the notion of an Expr element whose @kind attribute is the string ”literal”,
Expr[@kind="literal"] is written.
By using the RVC-CAL model, FNL also allows networks of FUs and individual FUs to be parameterized. In
particular, it is possible to pass bounded values for specific parameters into FU and/or FU networks. These
values are represented by Expr and Decl syntax. Expr and Decl are the syntactical constructs describing a
computation, which may, itself, be dependent upon the values of parameters which are either global or local
variables.
5 Bitstream syntax description
The MPEG Video Tool Library contains FUs that specify MPEG decoding algorithms. A new decoder
configuration implies new bitstream syntax. The description of the bitstream syntax in RVC is provided using
BSDL as specified in ISO/IEC 23001-5 and BSDL schema. However, to facilitate the developments of
synthesis tools that are able to generate parsers directly from a BSD (i.e. a BSDL schema), the RVC
framework standardizes a version of BSDL called RVC-BSDL specified by including new RVC specific
extensions and usage restrictions of standard BSDL in ISO/IEC 23001-5. Such extensions and restrictions
versus the MPEG standard BSDL are defined in Annex C of this document. RVC-BSDL contains all
information necessary to parse any bitstream compliant with such syntax. The procedure to instantiate the
parser capable of parsing and decoding any bitstream compliant with the syntax specified by the RVC-BSDL
schema is not normative. Examples of such non-normative procedures are provided in Annex D.
6 Model instantiation
This Clause describes the “model instantiation” process which consists of the selection of Functional Units
(FUs) from the Video Tool Libraries and instantiation of the FUs with the proper parameter assignments. The
instantiation process requires the following information:
• The Video Tool Libraries
• The FU network description
• The bitstream syntax description
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ISO/IEC 23001-4:2009(E)
The instantiation process consists of attaching source codes corresponding to the FUs identified in the FND in
order to build a complete model, which can be simulated. The Video Tool Libraries are repositories of source
code for each Functional Units. The FND contains only the references (name of the FUs) to the pieces of code
in the VTLs. The process outputs the ADM, which is the result of the gathering of all the pieces of code of all
FUs. Figure 6, illustrates the Model Instantiation process.
Figure 6 — Description of the model instantiation process
The FU Network Description (FND) provides the structure of the decoder by giving the names of the FUs
composing the decoder and their respective connections between each other. The name of the instance of the
FU in the ADM is contained in the tag . The tag indicates the
name of the FU (in the video tool library) from which the FU of the ADM must be instantiated. The tag
provides the values of the parameters, which must be used for the instantiation of the FU in
the ADM.
The Bitstream Syntax Description (BSD) provides the structure of the bitstream. The parser is generated
automatically from the BSD. Informative examples are provided in Annex E for building the parser. The syntax
parser FU of the ADM might use other FUs to parse the bitstream. Thus, a clear link between identifiers inside
the BSD and the FND must be established. The tag indicates the name of the instance of
the FU into the ADM to which this element of syntax is sent.
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ISO/IEC 23001-4:2009(E)
Annex A
(normative)
Functional unit network description
A.1 Elements of a functional unit network
XDF — A FU network is identified by the root element called XDF that marks the beginning and end of the
XML description of the network.
• optional attribute: @name, the name of the network. @version, the version number of the current
network. Assumed to be ”1.0” if absent.
• optional children: Package, Decl, Port, Instance, Connection.
.
Package — This element contains a structured representation of a qualified identifier (QID) (i.e. a list of
identifiers that are used to specify a locus in a hierarchical namespace). That QID provides the context for the
@name attributed of the enclosing Network element: that name is intended to be valid within the specified
namespace, or package.
• required child: QID, the qualified identifier.
Decl[@kind="Param"] — Represents the declaration of a parameter of the network.
• required attribute: @name, the name of the parameter.
• optional child: Type, the declared type of the parameter.
Decl[@kind="Var"] — This element represents a variable declaration. Variables are used within expressions
to compute parameter values for actors instantiated within the network and within expressions used to
compute the values of other variables.
• required attribute: @name, containing the name of the declared variable.
• required child: Expr, representing the expression defining the value of this variable, possibly referring
the values of other variables and parameters.
• optional child: Type, the declared type of the variable.
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Port — Represents the declaration of a port of the network. Ports are directed, i.e. they serve as either input
or output of tokens.
• required attributes: @name, the name of the port. @kind, either ”Input” or ”Output”.
• optional children: Type, the declared type of the port.
Instance — This element represents instantiations of FUs (i.e. actors). Essentially, an instantiation consists of
two parts: (1) a specification of the class of the FU, and (2) a list of parameter values, specifying expressions
for computing the actual parameter for each formal parameter of the FU class.
• required attribute: @id, the unique identifier of this FU instance in the network. No two Instance
elements may have the same value for this attribute.
• required child: Class, identifying the FU class to be instantiated.
• optional children: Parameter, each of these is assigning a formal parameter of the FU class to an
expression defining the actual parameter value for this instance. Attribute, additional named attributes
for this instance.
Connection — Represents a directed connection between two ports within the network. The source of that
connection can be either an input port of the network or an output port of a FU instance. Conversely, the
destination of that connection is either an output port of the network or the input port of an FU instance.
• required attributes: @src, the id of the source FU of this connection. If ””, the connection originates at
a network input port. @src-port, the name of the source port. @dst, the id of the destination FU of this
connection. If ””, the connection ends at a network output port. @dst-port, the destination port of the
connection.
• optional children: Attribute, additionally named attributes of this connection.
port="out"/>
A.2 Expressions
All Expr elements represent expressions. Expressions are used to compute values that are in turn passed as
parameters when instantiating FUs. Expressions can refer to variables by name. Those variables may be
declared local variables of a network, declared network parameters, or global variables. There are a number
of different kinds of expressions, all represented as Expr elements. They are distinguished by the @kind
attribute.
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Expr[@kind="Literal"] — These expressions represent literals, which are essentially atomic expressions that
denote constants, and which do not refer to any variables. There
...
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