1、INTERNATIONAL STANDARD ISOIIEC 14478-3 First edition 1998-12-15 Information technology - Computer graphics and image processing - Presentation Environment for Multimedia Objects (PREMO) - Part 3: Multimedia Systems Services Technologies de /information - lnfographie et traitement dimages - Environne
2、ment de prrfuu/Connecrion object . 36 10.7.3.2 VirrunlConnerrionMulticast object . 38 10.7.4 Groupobject., . .39 10.7.5 LogicalDevice object. .40 11 Component specification 41 A Overview of PREMO MSS objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 B A typical example sce
3、nario for MSS usage . 44 C Basic Devices . 46 C. I Format objects .47 C.l.1 Videoformats .47 C.l.2 Audio formats .48 C.l.3 CATV format. .49 C.l.4 MIDI format . .49 C.2 Digital stream controls .49 C.3 Video and audio processing .49 C.3. I Video processing. . .49 C.3.2 Audio processing. 50 C.4 Specifi
4、c devices . .50 C.4.1 Defining a device 50 C.4.2 Video5 I C.4.3 Audio5 I C.4.4 Files.5 2 C.4.5 CDplayer5 2 C.4.6 CATVtuner.5 2 C.4.7 MlDldevice 5 3 C.4.8 External resources. .53 C.5 Functional Specification. .54 C.5. I Area of interest for video objects 54 C.5.2 Format objects. . .54 C.5.3 Digital S
5、tream Control . .62 C.5.4 Video and audio processing . .63 C.5.5 Specific devices. . 65 D Examples of virtual connection settings . 72 D. I Hardware connection example. . .72 D.2 Direct connection example. .72 D.3 Local connection example . .72 D.4 Network connection example. .74 0 ISO/IEC ISO/IEC 1
6、4478-3: 1998(E) Foreword IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardi- zation. National bodies that are members of IS0 or IEC participate in the development of International Standa
7、rds through technical committees established by the respective organization to deal with particular fields of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other international organizations, government and non-governmental, in liaison with IS0 and IEC
8、, also take part in the work. In the field of information technology, IS0 and IEC have established a joint technical committee ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committees are circulated to the national bodies for voting. Publication as an Interna- tional St
9、andard requires approval by at least 75% of the national bodies casting a vote. ISO/IEC 14478-3 was prepared by Joint Technical Committee ISO/IEC JTC 1, Infor- mation technology, Subcommittee SC24, Computer graphics and image processing. This International Standard currently consists of the followin
10、g four parts under the general title Information technology - Computer graphics and image processing - Presentation environments for multimedia objects (PREMO): - Part I: Fundamentals of PREMO - Part 2: Foundation Component - Part 3: Multimedia Systems Services - Part 4: Modelling, Rendering, and in
11、teraction Component Annex A forms an integral part of this part of ISO/IEC 14478. Annexes B to D are for information only. ISO/IEC 14478-3: 1998(E) Introduction 0 ISO/IEC The Multimedia Systems Services (MSS) component of PJUZMO provides a standard set of services that can be used by multimedia appl
12、ication developers in a variety of computing environments. Enabling multimedia applications in a heterogeneous, dis- tributed computing environment is the design motivation for the MSS. This is an in- creasingly prevalent computing model, and a solution that meets the needs of this environment can m
13、ore easily be scaIed to stand-alone systems than vice versa. The principal reasons for defining the MSS are: a) provide abstractions and mechanisms that make it possible for applications to deal with the problems of distributed multimedia computing successfully; b) facilitate the implementation of c
14、ompIex applications, such as video confer- encing; c) provide abstractions that make it possible for applications to deal with media devices without regard to specific characteristics of the platform, attached devices, or the network(s) connecting the platforms and devices; d) to provide a standard
15、methodology, especially for handling “live” data; e) insure scalability to large organizations; f-l insure adequate performance in adverse conditions; g) facilitate Quality of Service commitments; and h) consider the time critical nature of the data. The primary goal of the MSS is to provide an infr
16、astructure for building multimedia computing platforms that support interactive multimedia applications dealing with synchronized, time-based media in a heterogeneous distributed environment. Opera- tion in a distributed environment is important because of significant trends in the com- puter indust
17、ry towards client/server and collaborative computing. Another significant trend is towards multimedia enabled computing. The inevitable result will be an inter- section of these trends to produce a distributed multimedia environment with a topol- ogy similar to Figure I. The MSS is intended to addre
18、ss a broad range of application needs. It extends the mul- timedia capabilities of stand-alone computers to capabilities that are usable both local- ly and remotely. The Multimedia Systems Services gives applications the ability to handle: Vi 0 ISO/IEC ISO/-IEC 14478-3:1998(E) i) live data remotely;
19、 j) stored data remotely; k) both live and stored data simultaneously; I) multiple kinds of data simultaneously; and m) new kinds of devices and media types. Application 1 Figure 1 - Distributed multimedia environment vii ISO/IEC 14478-3:1998(E) 0 ISO/IEC To provide support for remote media device c
20、ontrol and remote media access that de- rive from the above application scenarios, the Multimedia System Services uses two distinct mechanisms. To support interaction with remote objects, the Multimedia Sys- tems Services depends upon an underlying object model and infrastructure, as de- scribed in
21、ISO/IEC 14478-I (PREMO). To support the media independent streaming of time critical data, the Multimedia Systems Services defines a Media Stream Con- trol. The MSS does not address: n) encryption and security; o) intellectual property rights and accounting; p) scripting; q) user interfaces; or f) s
22、haring of data between applications. VIII INTERNATIONAL STANDARD 0 ISOLIEC ISO/IEC 1447 b) provision of an abstract type for the data tlow path or the connection between media processing nodes, encapsulating low-level connection and transport semantics; c) grouping of multiple processing nodes and c
23、onnections into a single unit for purposes of resource reservation and stream control; d) provision of a media dataflow abstraction, with support for a variety of position, time and/or synchronization capabili- ties: e) separation of the media format abstractions from the dataflow abstraction; f) sy
24、nchronous exceptions and asynchronous events; g) application visible characterization of object capabilities; h) registration of objects in a distributed environment by location and capabilities; i) retrieval of objects in a distributed environment by location and constraints; j) definition of a Med
25、ia Stream Protocol to support media independent transport and synchronization. The Multimedia Systems Services rely on the object model of ISO/IEC 14478-I (Fundamentals of PREMO) and the object types and non-object data types defined in ISO/IEC 14478-2 (PREMO Foundation Component). ISO/IEC 14478-3:1
26、998(E) 0 ISO/IEC 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO/IEC 14478. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agree- m
27、ents based on this part of this international standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. ISO/IEC 14478- 1: 1998, Information techno
28、logy - Computer graphics and image processing - Presentation Environment for Multimedia Objects (PREMO) - Part I: Fundamentals of PREMO. ISOIIEC 14478-2: 1998, Information technology - Computer graphics and image processing - Presentation Environment for Multimedia Objects (PREMO) -Part 2: Foundatio
29、n Component. ISOIIEC 14478-4: 1998, Information technology - Computer graphics and image processing - Presentution Environment for Multimedia Objects (PREMO - Part 4: ModeRing, Rendering, and Interaction Component. ISOtIEC 109 18- 1: 1994, Information technology - Digital Compression and Coding of C
30、ontinuous-Tone Still Images (JPEG). ISOIIEC 1 1172: 1992, Information technology - Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about I.SMbit/s (MPEG). 3 Definitions 3.1 PREMO Part 1 dehititms This part of ISO/IEC 14478 makes use of all terms defined in ISO/IEC 1
31、4478-l (Fundamentals of PREMO). 3.2 PREMO Part 2 definitions This part of ISO/lEC 14478 makes use of all terms defined in ISO/IEC 14478-2 (PREMO Foundation Component). 3.3 Additional definitions For the purposes of this part of ISO/IEC 14478, the following definitions apply. 3.2.1 configuration obje
32、cts: Collective name for format, quality of service descriptor, and media stream protocol objects. 3.2.2 jitter: Delay variance. 3.2.3 processing element (for virtual devices): Conceptual entity describing the internal behaviour of virtual device ob- jects. 3.2.4 virtual connection adapter: Conceptu
33、al entity describing the configuration process performed by a virtual connec- tion object. 3.2.5 unicast connection: One-to-one connection; an output port may be connected to one input port only, and an input port may be connected to one output port only. 3.2.6 multicast connection: One-to-many conn
34、ection; an output port may be connected to several input ports, and an in- put port may be connected to several output ports. The following alphabetical list gives the subclause of each definition. configuration objects 3.2.1 jitter 3.2.2 2 0 ISO/IEC ISO/IEC 14478-3: 1998(E) multicast connection pro
35、cessing element (for virtual devices) unicast connection virtual connection adapter 3.2.6 3.2.3 3.2.5 3.2.4 4 Symbols and abbreviations ATM: Asynchronous Transfer Mode. CATV: Cable TV DMA: Direct Memory Access. FSM: Finite State Machine. IEC: International Electrotechnical Commission. IS: Internatio
36、nal Standard. ISO: International Organization for Standardization. JPEG: Joint Picture Experts Group. LAN: Local Area Network MIDI: Musical Instrument Digital Interface MPEG: Moving Picture Experts Group. MSS: Multimedia Systems Services PREMO: Presentation Environment for Multimedia Objects. QoS: Q
37、uality of Service. TCP: Transmission Control Protocol. UDP: User Data Protocol. RTP: Real-Time Protocol 5 Conformance A conforming implementation of the PREMO Multimedia Systems Services shall comply with the general conformance rules defined in clause 5 of ISO/IEC 14478-l and the component specific
38、ation in clause 1 I of This part of ISO/IEC 14478. 6 Overview of the Multimedia Systems Services 6.1 Introduction This clause presents several comprehensive views of the Multimedia Systems Services, which, taken together, represent a broad, architectural summary. These views include: a) an object in
39、teraction diagram, which characterizes the dynamic relationships among instantiated objects and to illustrate client visible interfaces; b) a subtyping diagram, which describes the subtyping hierarchy among MSS objects; c) a short description of the life cycle of Multimedia Systems Services objects.
40、 ISO/IEC 1447 Figure 3 on page 6 summarizes the interaction among framework objects. As seen in Figure 2, only a subset of the objects and interfaces are actually visible to a client of MSS. In particular, much of the interaction between the virtual connection and other objects in the framework is n
41、ot client visible. This part of ISO/IEC 14478 is concerned primarily with client visible interfaces; implemen- tations may extend these interfaces for implementation-specific reasons, to comply with the behaviour of the objects, as defined in this standard. Figure 2 is suggestive, rather than realis
42、tic, since the objects shown are abstract types, rather than concrete types which would normally be instantiated. Also, object creation and destruction are not shown in this diagram. 4 0 ISO/IEC ISO/IEC 14478-3: 1998(E) In Figure 2, the client is communicating with a small dataflow graph, comprised
43、of two virtual devices and a virtual connection. A group object, which assists the client, is also shown. The client interacts with the objects indicated by the arrows. Each of these objects may be local or remote. Each virtual device is a processing node in the dataflow graph. The nature of the pro
44、cessing (capture, encoding, filtering, etc.) varies according to the specific object (and is implemented by subtyping). Each virtual device contains a stream control object and one or more format objects shown by the boxes in the shaded areas. Virtual connections and groups also have an associated s
45、tream object and this association is represented similarly. These associations are referred to as inclusion. Although not explicitly shown in the diagram, the client interacts directly with the included stream and format interfaces. A stream control object provides the client with an interface to ob
46、serve media stream position in various terms (as a function of media transport, media samples, or logical time; see clause 8). Stream control objects also provide sgnchronization operations. Stream control objects do nor perform the effective transfer of media data; they merely act as an entry for t
47、he clients to control media flow. In addition to a stream control, a virtual device also contains one or more ports, describing an input or output mechanism for the virtual device. Ports are framework abstractions that do not have a client-visible interface. Virtual devices provide operations to sel
48、ect a specific port, using an abstract non-object data type as an opaque handle. Just as the stream control object allows a media stream control abstraction which is separable from media processing, the format object provides an abstraction of the details of media formatting which is separate from b
49、oth processing and flow-control. For example, the details of a frame-dependent video encoding, like MPEG, would be represented by a subtype of format. The virtual connection provides operations to create a connection between an output port of one virtual device and an input port of another, fully encapsulating low-level transport semantics. Virtual connections also provide support for multicast connections. An included stream object provides operations for controlling the dataflow on the virtual connection. The group object, shown in Figure 2, provides assistance to the client to manage t
