Operating System support for Multimedia

1
Operating System support for Multimedia

• QoS (Quality of Service) in Multimedia OS
• Ashish Ranjan
• Multimedia File System
• Jaydeep Punde
• CPU Scheduling in Multimedia OS
• Arun Singal

2
Operating system

• Operating system is responsible for orderly and
  controlled allocation of resources among the
  various executing programs competing for them.
• Main emphasis of commodity OS (unix, NT) is to
  reach fairness and efficiency.
• No guarantee given to an application for timely
  execution.

3
Multimedia characteristics

• Multimedia needs real time support.
• If data is not processed at certain pace and
  within a certain deadline the data looses its
  meaning.
• Adhering to deadlines is desirable but not
  absolutely necessary, i.e it is soft real time in
  nature.

4
Problems with existing systems

• Does not support soft real time characteristic of
  multimedia stream.
• When real time algorithms applied, other
  application starve.
• Need to support all types of application, i.e
  both best effort and real time.

5
Problems Cont.....

• No existing algorithm to satisfy both best effort
  and real time need.
• So, how to schedule/reserve resources for
  application?

6
QoS Paradigm

• QoS means to provide reliable and efficient data
  delivery service.
• To support all types of application, a middleware
  necessary to manage resources.
• Encompasses both HRT and SRT paradigm.
• Provides probabilistic assurance that resource
  requirement will be satisfied a certain fraction
  of time.

7
QoS Requirements

• Multimedia QoS requirement as described by the
  high level parameters are
• Throughput
• Delay
• Jitter
• reliability

8
Resource Management and QoS

• Tasks
• Specification
• It is concerned with capturing application level
  quality of service requirements and management
  policies
• QoS mapping
• This is concerned with converting the high level
  specification into actual resource level
  parameters (low level parameters)

9
Tasks Contd....

• Admission control
• includes a test whether enough resources are
  available to satisfy the request without
  interfering with the previously granted request
• allocation and scheduling
• This is where actual resources are allocated and
  scheduled
• Accounting/Policing
• implies tracking down the resources consumed by
  the task
• Deallocation

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Task Contd...
QoS Specification
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Mapping

• Why Mapping is necessary?
• QoS parametres are specified at a high level
• Exact resource requirement are not known to
  application

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QoS Mapping

• Scaling
• As the data passes trough different layers of
  protocol, protocol headers are attached to the
  frame, which increases its size, and hence
  scaling of required application bandwidth is done
• Delay Partioning
• The delay is partitioned across each module.

13
Bottlenecks for providing QoS

• QoS should be supported at all layers of
  communication
• Data packets from the network are processed in
  First in first out basis for all connection
• Kernel do a lot of hidden processing with high
  priority
• The layered architecture of the communication
  systems may imply considerable data movement in
  the protocols
• Accounting in OS.

14
Nemesis

• Designed with a view to support QoS paradigm
• Single address space to avoid context swithching

15
QoS in Nemesis
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Conclusion

• QoS paradigm encompasses both HRT and SRT and
  hence is best suited for multimedia system.
• QoS should be provided at each layer to achieve
  the desired goal.

17
References

• 1 Ralf Steinmetz ,"Analyzing the Multimedia
  Operating System", IEEE MultiMedia, 2, 1, pp
  68-84 (Spring 1995).
• 2 T.Plagemann, V.Goebel, P.Halvorsen, O.
  Anshus, "Operating system support for multimedia
  systems",Computer communications,23,3,pp
  267-289,(2000).
• 4 P. Goyal and X. Guo and H. Vin "A
  hierarchical CPU scheduler for multimedia
  operating systems ", In Proceedings of the
  Second Symposium on Operating Systems Design and
  Implementation (OSDI). USENIX, October 1996.

18
References

• 5 Schulzrinne, H., "Operating System Issues for
  Continuous Media," Multimedia Systems, vol. 4,
  pp. 269--280, Oct. 1996.