Docstoc

The Multimidia in Distributed System

Document Sample
The Multimidia in Distributed System Powered By Docstoc
					Distributed multimedia



  Presented by Mingyang Gu
        Nov. 4th, 2002


                             1
Introduction to the Book
         <<Open distributed processing and
                     multimedia>>
   The book evaluates the requirements
    imposed by multimedia computing
   The book also proposes an approach of
    distributed system to meet the requirements




                                           2
Index about the presentation
   Introduction to distributed multimedia
    •   Introduction to distributed system
    •   Introduction to multimedia
    •   The special requirements and challenges
   Requirements of distributed multimedia
    applications
    •   Examining each requirements in more depth
    •   Making a checklist of requirements
    •   Some various standards and platforms are considered
        with respect to the checklist


                                                     3
Introduction to distributed
       multimedia



       The first chapter



                           4
The main topics of this chapter
   Introduction to distributed system
   Introduction to multimedia
   The special requirements and
    challenges




                                         5
What is a distributed system
   A distributed system is a system designed to
   support the development of applications and
   services which can exploit a physical
   architecture consisting of mulitple,
   autonomous processing elements that do not
   share primary memory but cooperate by
   sending asynchronous messages over a
   communications network.



                                          6
Advantages of distributed
system
   Resource sharing
   Availability (redundancy)
   Extensibility
   Performance
   Distributed organizations (Companys,
    groups, devices are widly distributed)


                                         7
Problems introduced by a
distributed environment
   A definition concerned the problems by
    Leslie Lamport:
    • A distributed system is one that stops you
      getting any work done when a machine
      you’ve never even heard of crashes.




                                               8
Problems introduced by a
distributed environment
   Services can be accessed concurrently by a
    number of different client applications.(conflict)
   Distributed systems suffer partial failures (it is
    hard to find out the cause of failure)
   Difficulties also exist in locating the right server
    in a distributed environment.(migration)
   Servers might be replicated to enhance
    availability.(consistency)



                                                  9
Problems introduced by a
distributed environment
   Certain level of transparency is the resolution
    to this problem
    • It is hard for programmer to deal with all the
        problmes
    •   Full distribution transparency would carry a
        performance overhead in accessing servers
    •   Modern thinking is to provide selective transparency,
        where the application programmer can specify the
        required level of transparency



                                                        10
Important trends in distributed
processing
   Large scale: such as internet, it is hard to
    manage because the technologies and
    administrative domains are also very large
   A convergence between distributed systems
    and telecommunications architectures.
   More heterogeneous




                                             11
Focus on heterogeneity
 • Heterogeneous hardware
   • Computers, networks
 • Heterogeneous platforms
   • Operating systems
 • Heterogeneous languages
   • Development languages
 • Heterogeneous management policies
   • Different policies have different influences on
     security, administration, naming and configuration
     control


                                                   12
The goal of open distributed
processing
   In simple terms, the goal of open
    distributed processing is to enable
    interaction with services from anywhere
    in the distributed environment without
    concern with services from anywhere in
    the distributed environment without
    concern for the underlying environment.


                                       13
The goal of open distributed
processing
   Openness and distributed processing
    • Conformming to well-defined interface
    • The conformance testing procedures to
      ensure that different implementations by
      different manufacturers adhere to the
      standardized interfaces.
       • Interoperability (platform)
       • Portability (application)


                                                 14
The goal of open distributed
processing
•   Self-open architecture to the components which show the
    advantages:
     • The benefits of interoperability and portability extend to all
         components in the architecture.
     •   The architecture can be specialized or can evolve by changing
         the implementation of individual components.
     •   The architecture can be extended by introducing new
         components at a later date




                                                                 15
The different levels of openness
                                                         x,y,z
          ?,?,?                   x,y,z

                                                                  h,j

                                                         c,d




                                                   a,b           e,f




   Closed system, the     The interface is       The interfaces of the
   interface is private   published and          system and the
   and unknown to         conferm to a           components are all
   global                 standard, but the      published and
                          internal details are   conform to a
                          unknown                standard




                                                                         16
    Achieving the goal- how to deal
    with heterogeneity
   The resolution is providing independence
    •   Hardware independence
         •   Providing abstractions over the characteristics of the underlying
             physical environment, such as network protocol, standard interchange
             format
    •   Platform independence
         •   Provideng a set of agreed abstractions over system resources, such as
             virtual memory, file storage and processing
    •   Language independence
         •   Provide abstractions over the interfaces offered by different languages
    •   Management independence
         •   Providing a meta-architecture for management



                                                                         17
Standards organizations and the
standards
   International agreement and high level
    of confidence to the standard
   Two styles of standards organization:
    • International treaty-based, such as ISO, ITU.
    • Industrial consortia, such as OSF, OMG.
    • Alternatively, standards emerge when
      achieving a certain level of market
      penetration: IBM-compatible PC, SUN Java.


                                              18
Standards organizations and the
standards
   ISO/ITU-T reference model for open
    distributed processing (RM-ODP).
   OMG common object request broker
    architecture (CORBA).
   The open group’s distributed computing
    environment (DCE).



                                      19
Introduction to multimedia
   Media:
    •   The term media refers to the storage, transmission,
        interchange, presentation, representation and
        perception of different information types, such as text,
        graphics, voice, audio and video.
   Multimedia
    •   The term multimedia is to denote the property of
        handling a variety of representation media in an
        integrated manner. (how information is described in an
        abstract form)


                                                          20
The motivation of distributed
multimedia systems
   End user pull
    • Faced information overload and information
      starvation, the end user need the support to
      get the right information to right people, in
      right time and in right form.
   Technology push
    • The technology is emerging to support
      multimedia computing continuously.


                                               21
Continuous and discrete media
types
   Continuous media:
    • Having an implied temporal dimension: items
      of data must be presented according to
      particular real-time constraints for a particular
      length of time, such as audio, video,
      animation
   Discrete media:
    • No temporal dimension, such as text, graphic

                                                  22
Assessment of the demands of
digital media
Different type of digital media have different
requirement for storage or transmission.

 Media type            Average bandwidth(Mbits/s)

 Voice                 0.064
 High-fidelity audio   1.0
 Slow scan video       80
 High-quality video    200



                                                    23
Compression
   The requirement can reduce using the
    technology of compression
    Standard   Standardization     Symmetry         Coding     Compression
                                                                  rateio
     JPEG      ISO/CCITT,        Symmetrical    Intra-frame   <70:1
               1990
     MPEG-1    ISO,1992          Asymmetrical   Intra-frame   <200:1
                                                Inter-frame
     MPEG-2    ISO Work Item     Asymmetrical   Intra-frame   <200:1
                                                Inter-frame
     H.261     CCITT, 1990       Asymmetrical   Intra-frame   100:1 – 2000:1
                                                Inter-frame




                                                                       24
The challenge of multimedia for
open distributed processing
   Support for continuous media
        •   The transfering of continuous media needs relatively long
            periods of time
   Quality of service management
        •   Static aspect: quality of service specification, negotiation,
            resource reservation and admission control
        •   Dynamic aspect: quality of service monitoring and
            renegotiation
   Real-time synchronization
        •   Intra-media and inter-media synchronization
   Multiparty communication
        •   Programming model, system support, quality of service, policy
            about ordering


                                                                      25
summary
   The first part of this chapter concerns the
    topic of open distributed processing.
   The second part is mainly about
    introduction to multimedia and
    distributed multimedia system.




                                          26
Standards and platforms
  for open distributed
       processing


     The second chapter



                          27
The main points in this chapter
   Three major initiatives in the field:
    • ISO’s Reference Model for Open Distributed
        Processing (RM-ODP)
    •   OMG’s Common Object Request Broker
        Architecture (CORBA)
    •   Open Groups’s Distributed Computing
        Environment (DCE)




                                              28
   Requirements of
distributed multimedia
      applciations


     The third chapter



                         29
The main topics of this chapter
   Examining each requirements in more
    depth
   Making a checklist of requirements
   Some various standards and platforms
    are considered with respect to the
    checklist



                                     30
The requirements of distributed
multimedia application
   Support for continuous media
   Quality of service management
   Real-time synchronization
   Multiparty communication




                                    31
Suporting continuous media
   Programming models for continuous
    media
    • Existing programming models (fit for discrete
      interaction)
       • Asynchronous or synchronous message
         passing(TCP/UDP)
       • Remote procedure calls(RMI)
       • Object invocation(CORBA)


                                               32
Suporting continuous media
 •   The continuous media is not better to be modelled by
     a sequence of discrete interactions
      • Place an unnecessary burden on the programmer in
          terms of repeatedly initiating interaction
      •   The programmer would have to specify requirements on
          each individual interaction
      •   The solution prescribes one approach to the interaction
          and does not give the system the required level of
          freedom to make optimizations.




                                                          33
Suporting continuous media
   System support for continuous media
    • The real-time relationship between individual
        components of continuous media needs more
        the system support, such as 25+/-5 frame per
        second demand in video displaying
    •   In many cases, special techniues will be
        required to deal with continuous media types,
        such as TCP/UDP does not fit for continuous
        transmission

                                                34
Suporting continuous media
   Styles of stream interaction
    • Two broad classes of stream interaction
       • Simple streams
       • Complex streams
    • For continuous media, it’s neccessary to
      provide support for both simple and complex
      streams where both styles of stream have
      different charateristics


                                            35
Quality of service management
   Definition
    • Quality of service management is defined as
      the necessary supervision and control to
      ensure that the desired quality of service
      properties are attained and sustained
   In a multimedia system, the QoS is
    central to the application.
    • Traditional: meet or not
    • Much more contents in a multimedia system

                                                   36
Quality of service management
   Fundamentals of QoS
    •    Qos categories in distributed multimedia system
           •   Timeliness
           •   Volume
           •   Reliability
    •   Qos dimensions
        Qos dimensions          Measures for stream            Measures for discrete
                                interactions                   interactions
        Timeliness dimension    End-to-end latency of          End-to-end latency of
                                frames;                        interactions
                                permitted jitter on latency
        Volume dimension        Perceived throughput in        Perceived throughput in
                                frames per second              bytes per second
        Reliability dimension   % loss of frames;              Bit error rates in
                                bit error rate within frames   individual interactions




                                                                                         37
Quality of service management
 • Expressing quality of service requirements
    • Deterministically: precise values
    • Using proabilities: probability to get the quality
    • Stochastic distributions:
 • Different classes of quality of service: best
   effort and guaranteed




                                                  38
Quality of service management
 • QoS dependencies and contracts
   • Quality of service at one part of the
     system will depend on quality of service
     in another part
   • A QoS dependency is a relation between
     the object offering a service and one or
     more objects supporting this service
   • Qos contract refers to the requirements
     expression about the quality of service
     and the dependencies that this quality of
     service might have on other objects

                                                 39
Quality of service management
 • QoS and viewpoints
   • Enterprise viewpoint
   • Information viewpoint
   • Computational viewpoint
   • Engineering viewpoint
   • Technology viewpoint




                               40
Quality of service management
   Fundamentals of Qos management
    • Static Qos management (establishment)
      • QoS specification & QoS negotiation
      • Admission control & resource reservation
    • Dynamic Qos management (ongoing
     provision)
      • QoS monitoring, QoS policing & QoS maintenance
      • QoS renegotiation


                                                   41
Real-time synchronization
   Two styles of real-time synchronization
    •   Intra-media
    •   Inter-media
   Other considerations
    •   Both intra- and inter-media synchronization must
        operate correctly in a distributed environment.
    •   It is required that the actions to maintain real-time
        synchronization can be determined dynamically – at
        run-time.



                                                         42
Multiparty communications
   Programming models and systems
    support
    • This model should support a variety of styles
        of multicast including 1 ->N, N->1, and M->N.
    •   The programming model should enable the
        management of the resultant groups.
    •   Without systems support, the bandwidth
        requirements of multiparty stream interactions
        would be overloaded.

                                                43
Multiparty communications
   Impact on QoS management
    • The receivers may require different qualities
      of service.
                                                  A
                                                  B
                              F1                  C
     sender
              router

                       Sender+filter
                                       F2         D
                                            receiver




                                                       44
Multiparty communications
   Impact on synchronization
    • It’s important to be able to support a variety of
      policies for ordering data delivery, such as
      total ordering, attribute ordering, partial
      ordering, causal ordering ...




                                                 45
Checklist of requirements
   Continuous media interactions
    •   Programming model for both simple and complex
        streams
    •   Access and manipulate continuous media data
    •   Underlying system support for streams
   QoS management
    •   Deterministic, probabilistic or stochastic
    •   Classes of service
    •   QoS contracts feature
    •   Static QoS management
    •   Dynamic QoS management

                                                     46
Checklist of requirements (cont)
   Real-time synchronization
    •   Intra-media synchronization
    •   Inter-media synchronization
    •   Arbitrary distributed configuration
    •   Run-time configuration
   Multiparty communication
    •   Discrete and stream group interactions
    •   Establishment and management of multiparty
        communications
    •   Different requirement of QoS
    •   Synchronization policies

                                                     47
Responses to the challenge
   CORBA and MSS
   DCE
   RM-ODP and TINA




                             48
     Thank you!



Presented by Mingyang Gu
      Nov. 4th, 2002


                           49

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:5/20/2013
language:Unknown
pages:49