Distributed multimedia

1
Distributed multimedia

• Presented by Mingyang Gu
• Nov. 4th, 2002

2
Introduction to the Book

• ltltOpen distributed processing and multimediagtgt
• The book evaluates the requirements imposed by
  multimedia computing
• The book also proposes an approach of distributed
  system to meet the requirements

3
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

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Introduction to distributed multimedia

• The first chapter

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The main topics of this chapter

• Introduction to distributed system
• Introduction to multimedia
• The special requirements and challenges

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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.

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Advantages of distributed system

• Resource sharing
• Availability (redundancy)
• Extensibility
• Performance
• Distributed organizations (Companys, groups,
  devices are widly distributed)

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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 youve never
  even heard of crashes.

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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)

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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

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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

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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

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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.

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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)

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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

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The different levels of openness
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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

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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.

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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 groups distributed computing
  environment (DCE).

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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)

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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.

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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

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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
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Compression

• The requirement can reduce using the technology
  of compression

Standard Standardization Symmetry Coding Compression rateio
JPEG ISO/CCITT, 1990 Symmetrical Intra-frame lt701
MPEG-1 ISO,1992 Asymmetrical Intra-frame Inter-frame lt2001
MPEG-2 ISO Work Item Asymmetrical Intra-frame Inter-frame lt2001
H.261 CCITT, 1990 Asymmetrical Intra-frame Inter-frame 1001 20001
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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

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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.

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Standards and platforms for open distributed
processing

• The second chapter

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The main points in this chapter

• Three major initiatives in the field
• ISOs Reference Model for Open Distributed
  Processing (RM-ODP)
• OMGs Common Object Request Broker Architecture
  (CORBA)
• Open Groupss Distributed Computing Environment
  (DCE)

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Requirements of distributed multimedia
applciations

• The third chapter

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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

31
The requirements of distributed multimedia
application

• Support for continuous media
• Quality of service management
• Real-time synchronization
• Multiparty communication

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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)

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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.

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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

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Suporting continuous media

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

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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

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Quality of service management

• Fundamentals of QoS
• Qos categories in distributed multimedia system
• Timeliness
• Volume
• Reliability
• Qos dimensions

Qos dimensions Measures for stream interactions Measures for discrete interactions
Timeliness dimension End-to-end latency of frames permitted jitter on latency End-to-end latency of interactions
Volume dimension Perceived throughput in frames per second Perceived throughput in bytes per second
Reliability dimension loss of frames bit error rate within frames Bit error rates in individual interactions
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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

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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

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Quality of service management

• QoS and viewpoints
• Enterprise viewpoint
• Information viewpoint
• Computational viewpoint
• Engineering viewpoint
• Technology viewpoint

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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

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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.

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Multiparty communications

• Programming models and systems support
• This model should support a variety of styles of
  multicast including 1 -gtN, N-gt1, and M-gtN.
• The programming model should enable the
  management of the resultant groups.
• Without systems support, the bandwidth
  requirements of multiparty stream interactions
  would be overloaded.

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Multiparty communications

• Impact on QoS management
• The receivers may require different qualities of
  service.

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Multiparty communications

• Impact on synchronization
• Its important to be able to support a variety of
  policies for ordering data delivery, such as
  total ordering, attribute ordering, partial
  ordering, causal ordering ...

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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

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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

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Responses to the challenge

• CORBA and MSS
• DCE
• RM-ODP and TINA

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Thank you!

• Presented by Mingyang Gu
• Nov. 4th, 2002