1. Distributed Multimedia Systems
Distributed Systems
Topic 11:
Distributed Multimedia Systems
Dr. Michael R. Lyu
Computer Science & Engineering Department
The Chinese University of Hong Kong
In this topic, we will learn about Distributed Multimedia Systems and their applications.

2. 1 Outline Introduction Characters of multimedia data
Quality of service management
Resource management
Stream adaptation
Summary
First a brief introduction to distributed multimedia system is given.
Then, we talk about the characters of multimedia data.
After that, QoS management and resource management is discussed.
Then, stream adaptation is discussed.
Finally, a summary is given.

3. 1 Introduction Media: Multimedia
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 media representation in an integrated manner.
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.
Characteristics of continuous media
Continuously changing
Time critical
Large volume
Multimedia
The term multimedia is to denote the property of handling a variety of media representation in an integrated manner.
Multimedia Systems
Stringent real-time performance requirement
Deal with the processing of time-critical, large-volume
Performed in various layers:
In application, operating system, communication system, etc
 Need to a different Quality of Service mechanisms, requirements

4. 1 Introduction
Most multimedia is inherently time-based – the arrival time and arrival order of data packets is important
The Internet guarantees neither when transmitting data
We don’t just want interactive multimedia over our networks… we want it to be reliable and high-quality
A distributed multimedia system can come to the rescue
Most multimedia is inherently time-based – the arrival time and arrival order of data packets is important. Multimedia application demand the timely delivery of streams of multimedia data to end-users.
Audio and video streams are generated and consumed in real time, and the timely delivery of the individual elements (audio samples, video frames) is essential to the integrity of the application.
In short, multimedia systems are real-time systems: they must perform tasks and deliver results according to a schedule that is externally determine.
The Internet guarantees neither when transmitting data
We don’t just want interactive multimedia over our networks… we want it to be reliable and high-quality
A distributed multimedia system can come to the rescue
The degree to which that is achieved by the underlying system is known as the quality of service (QoS) enjoyed by an application.

5. 1 A Distributed Multimedia System
Applications:
non-interactive: net radio and TV, video-on-demand, e-learning, ...
interactive: voice &video conference, interactive TV, tele-medicine, multi-user games, live music, ...
This figure illustrates a typical distributed multimedia system capable of supporting a variety of applications, such as desktop conference, and providing access to stores video sequences, broadcast digital TV and radio.
The resources for which QoS management is required include network bandwidth, processor cycles and memory capacity.
Disk bandwidth at the video server may also be included.

6. 1.1 Multimedia in A Mobile Environment
Mobility support of multimedia delivery in a mobile environment is often provided by a backbone network (e.g., LAN or Internet), application domains, and access within each domain.
Multicast of multimedia messages can be sent from the servers through the backbone network to heterogeneous client terminals in different domains.
Multimedia services can also be provided from servers in one domain to clients in another domain. End-to-end (E2E) Quality of Service (QoS) should be provided.
Applications:
Emergency response systems, mobile commerce, phone service, entertainment, news video broadcasting services, games, ... *

7. 1.1 History
60s-70s: Distributed computing research with earliest networks
80s: Compact disc, personal computer explosion
80s-90s: Distributed multimedia system research (video conferencing, et al)
90s: Current prevalent paradigm (quality of service management)
60s-70s: Distributed computing research with earliest networks
80s: Compact disc, personal computer explosion
80s-90s: Distributed multimedia system research (video conferencing, et al)
90s: Current prevalent paradigm (quality of service management)

8. 1.1 Multimedia Application Samples
Web-based multimedia: It provides best-effort access to streams of audio and video data published via web.
Network phone and audio conferencing: It has relatively low bandwidth requirements, especially when efficient compression techniques are used
Video-on-demand services: These supply video information in digital form, retrieving the data from large online storage systems and delivering them to the end-user’s display
Some multimedia applications have been deployed even in today’s QoS-less, best-effort computing and network environments. These include:
Web-based multimedia: It provides best-effort access to streams of audio and video data published via web. They have need successful when there is little or no need for the synchronization of the data streams at different locations. Their performance is constrained by the limited bandwidth and variable latencies found in current networks and the inability of current operating systems to support real-time resource scheduling.
Network phone and audio conferencing: It has relatively low bandwidth requirements, especially when efficient compression techniques are used. But its interactive nature demands low round-trip delays, and these cannot always be achieved.
Video-on-demand services: These supply video information in digital form, retrieving the data from large online storage systems and delivering them to the end-user’s display
Requirements of the applications:
Low-latency communication
Synchronous distributed state
Media synchronization
External synchronization
Such applications will run success fully only in systems that include rigorous QoS management schemes.

9. 1.2 The Window of Scarcity
When dealing with large audio and video streams, many systems are constrained in the quantity and quality of streams they can support.
This situation has need depicted as the window of scarcity.
An important concept to note is the window of scarcity, which was theorized in the early 1990s. It refers to the availability of computing task resources at any given point in time.
Applied to a distributed multimedia system, it declares that, while all resources increase in the computing world over time, different computing tasks evolve at different times. For example, with our current computing systems, network file access is no longer a large processing task that we need to worry about. The processing of audio data requires far more processing power, but at this point in time desktop systems can handle it easily. The processing of video, however, is still a significant processing task on many computing systems.
The window of scarcity theory suggests that maintaining high quality levels in a distributed multimedia system is dependent on how well our computing systems can handle those kinds of distinct processing tasks, i.e., the more processing resources a specific task requires, the less are available for the overall system. As processing power increases, more and more resources for these distinct tasks become available, allowing for higher quality levels relative to the most processor-intensive tasks.
Many of today’s computer systems provide some capacity to handle multimedia data, but the necessary resources are very limited.
Especially when dealing with large audio and video streams, many systems are constrained in the quantity and quality of streams they can support.
This situation has need depicted as the window of scarcity.
While a certain class of applications lies within this windows, a system needs to allocate and schedule its resources carefully in order to provide the desired services.
Before the window of scarcity is reached, a system has insufficient resources to execute the relevant applications.
This was the situation for multimedia applications before the mid-1980s.
Once an application class left the window of scarcity, system performance will be sufficient to provide the service even under adverse circumstances and without customized mechanisms.
Advances in system performance are likely to be used to improved the quality of multimedia data to include higher frames rates and greater resolution for video streams or to support many media streams concurrently. But more demanding applications, including virtual reality and real-time stream manipulation, can extend the window of scarcity almost indefinitely.
The window of scarcity for computing
and communication resources

10. 2 Characteristics of Multimedia Applications
Large quantities of continuous data
Timely and smooth delivery is critical
Interactive multimedia applications require low round-trip delays
Need to co-exist with other applications
Reconfiguration is a common occurrence
Resources required:
Processor cycles in workstations and servers
Network bandwidth (+ latency)
Dedicated memory
Disk bandwidth (for stored media)
Large quantities of continuous data
Timely and smooth delivery is critical
deadlines
throughput and response time guarantees
Interactive multimedia applications require low round-trip delays
Need to co-exist with other applications
must not hog resources
Reconfiguration is a common occurrence
varying resource requirements
Resources required:
Processor cycles in workstations and servers
Network bandwidth (+ latency)
Dedicated memory
Disk bandwidth (for stored media)

11. 2 Characteristics of Multimedia Streams
Data rate
(approximate)
Sample or frame
frequency
size
Telephone speech
64 kbps
8 bits
8000/sec
CD-quality sound
1.4 Mbps
16 bits
44,000/sec
Standard TV video
(uncompressed)
120 Mbps
up to 640 x
480
pixels
24/sec
(MPEG-1 compressed)
1.5 Mbps
variable
HDTV video
1000–3000 Mbps
up to 1920
1080
24 bits
24–60/sec
MPEG-2 compressed)
10–30 Mbps
This figure described approaches to the allocation of scarce resources in order to achieve QoS.
Multimedia streams are often bulky. Hence systems that support multimedia applications need to move data with greater throughput than conventional systems. Above figure shows some typical data rates and frame/sample frequencies.
We note that the resource bandwidth requirements for some are very large.
This is especially so for video of reasonable quality.

12. 3 Quality of Service (QoS) Management
Simplicity in and of itself: We want and need high quality, reliable, interactive multimedia
The general Internet structure is not sufficient to accomplish this
A distributed multimedia system will add protocols and architectures on top of the Internet (or LAN) to guarantee quality levels, thereby satisfying our need
Allocate resources to application processes
according to their needs in order to achieve the desired quality of multimedia delivery
Scheduling and resource allocation in most current OS’s divides the resources equally amongst all processes
no limit on load. Therefore, can’t guarantee throughput or response time
Elements of Quality of Service (QoS) management
Admission control:
controls demand
QoS negotiation:
enables applications to negotiate admission and reconfigurations
Resource management:
guarantees availability of resources for admitted applications
real-time processor and other resource scheduling

13. 3 Infrastructure Components for Multimedia Applications
This application involves multiple concurrent processes in the PCs
Other applications may also be running concurrently on the same computers
They all share processing and network resources

14. 3 QoS Specifications for Application Components
Bandwidth
Latency
Loss rate
Resources required
Camera
Out:
10 frames/sec, raw video
640x480x16 bits
Zero A
Codec
In:
MPEG-1 stream
Interactive
Low
10 ms CPU each 100 ms;
10 Mbytes RAM B
Mixer
2 44 kbps audio
1 44 kbps audio
Very low
1 ms CPU each 100 ms;
1 Mbytes RAM H
Window
system
various
50 frame/sec framebuffer
5 ms CPU each 100 ms;
5 Mbytes RAM K
Network
connection
In/Out:
MPEG-1 stream, approx.
1.5 Mbps
1.5 Mbps, low-loss
stream protocol L
Audio 44 kbps
44 kbps, very low-loss
We set out resource requirements for the main software components and network connection.

15. 3 The QoS Manager’s Task Animation to reveal each step in the flow.
It shows the QoS manager’s responsibilities in the form of a flowchart.
On the software side, we need main and local QoS managers.
These can be developed internally, or can be purchased as a separate product.
The quality of the system will be directly related to the quality of the QoS managers.
The main manager should of course be connected in such as way as to accept client requests and to negotiate with the local QoS managers on the source computers.

16. 3.1 Quality of Services Negotiation
Bandwidth: data rate through a component
Latency: time needed for a packet to travel end to end
Jitter: the rate of change of latency
Loss rate: acceptable drop-frame ratio
Quality of service management: negotiation and allocation of computing resources
In order to understand how the various components of a distributed multimedia system interact, we should have clear notions of what its associated terms mean.
Bandwidth refers to the rate at which data can pass through a component, which is generally manifested as a network transmission line or bus. This term can also refer to the data rate needed to support a given sampled-data type, such as CD-audio or HDTV. It is known that audio data generally needs orders of magnitude more bandwidth than text data, and video data generally needs orders of magnitude more bandwidth than audio data.
Latency is the amount of time that it takes for one data packet to move through a transmission system from beginning to end. Obviously it is desirable for this to be as low as possible so that utilization of the stream of data packets at the destination can be smooth and regular. A high latency can cause problems in maintaining the time-based synchronicity of the data stream packets at the destination. 
Jitter is the rate of change of latency; it represents the speed-up or slow-down of packet transmission times. Rapidly changing latencies present problems for time-based data transmission that must be dealt with by quality of service managers using traffic shaping, scheduling, and other methods.
Loss rate refers to the ratio of acceptable packet loss per unit of time. We know that it is physically impossible to guarantee that all packets will be delivered on time and in order, especially in reference to the Internet, and so we must be ready to possibly drop or throw away packets if they violate those two conditions. The loss rate represents how much we are willing to do without.
Quality of service management is the explicit manipulation of resources from the source through the destination in order to provide a certain level of quality in regards to the delivered and processed data stream at the destination. Because multimedia data is time-based, QoS management is essential to yielding an experience that will meet users’ needs and expectations.

17. 3.1.1 Specifying QoS Parameters
The values of QoS parameters can be stated explicitly or implicitly
Bandwidth: Most video compression techniques produce a stream of frames of different sizes.
Latency: Some timing requirements in multimedia result from the stream itself.
Loss rate: Loss rate is the most difficult QoS parameter to specify.
The values of QoS parameters can be stated explicitly or implicitly
explicitly – e.g for the cameras output stream in Figure 15.4 of the textbook, we might require bandwidth: 50 Mbps, delay: 150 ms, loss: <1 frame I 10^3
Implicitly – e.g the bandwidth if the input stream to the network connection K is the result of applying MPEG-1 compression t the camera output.
Bandwidth: Most video compression techniques produce a stream of frames of different sizes depending on the original content of the raw video
Latency: Some timing requirements in multimedia result from the stream itself: if a frame of a stream does not get processed with the same rate at which frames arrive, backlog builds up and buffer capacity may be exceeded
Loss rate: Typical loss rate values result from probability calculations about overflowing buffers and delayed message. These calculations are either based on worst-case assumptions or on standard distributions

18. 3.1.2 Traffic Shaping Algorithms
Traffic shaping: using buffers at source and destination to smooth data flow
Token generator
(a) Leaky bucket
(b) Token bucket
Traffic shaping is the term used to describe the use of output buffering to smooth the flow of data elements.
The bandwidth parameter of a multimedia stream typically provides an idealistic approximation of the actual traffic pattern that will occur when the stream is transmitted.
The closer the actual traffic pattern matches the description, the better a system will be able to handle the traffic, in particular when it uses scheduling methods designed for periodic requests
A good illustration of this method is the image of a leaky bucket: the bucket can be filled arbitrarily with water until it is full; through a leak at the bottom of the bucket water will flow continuously.
(a) analogue of leaky bucket:
process 1 places data into a buffer in bursts
process 2 in scheduled to remove data regularly in smaller amounts
size of buffer, B, determines:
maximum permissible burst without loss
maximum delay
(b) Implements linear-bounded arrival processes (LBAP)
process 1 delivers data in bursts
process 2 generates tokens at a fixed rate
process 3 receives tokens and exploits them to deliver output as quickly as it gets data from process 1
Result: bursts in output can occur when some tokens have accumulated

19. 3.1.3 Flow Specification
Flow specification: explicit representation of required resources
Protocol version
Maximum transmission unit
Token bucket rate
Token bucket size
Maximum transmission rate
Minimum delay noticed
Maximum delay variation
Loss sensitivity
Burst loss sensitivity
Loss interval
Quality of guarantee
Bandwidth:
Delay:
Loss:
The RFC 1363 Flow Spec
A flow specification is the grouping of all relevant data regarding the transmission of multimedia data across a system. It spells out packet size, loss rate, acceptable latency, etc., for use by the quality of service manager(s). It is essential for creating a system with quality guarantees that rise above the free-for-all of an Ethernet/Internet unstructured implementation.
A collection of QoS parameters is typically known as a flow specification, or flow spec for short.
The flow spec reflect the QoS parameters discussed above in the following ways:
The maximum transmission unit and maximum transmission rate determine the maximum bandwidth required by the stream
The token bucket size and the rate determine the burstiness of the stream.
The delay characteristics are specified by the minimum delay that an application can notice ad max jitter it can accept.
The loss characteristics are defined by the total acceptable number of losses over a certain interval and the max number of consecutive losses.

20. 3.2 Admission Control
Admission control: allowing or denying client requests based on available resources
Bandwidth reservation
A common way to ensure QoS level for multimedia stream is to reserve some portion of resource bandwidth for its exclusive use.
Statistical multiplexing
It is based on the hypothesis that for large number of streams the required aggregate bandwidth remains nearly constant regardless of the bandwidth of individual streams.
Multimedia traffic may not obey this hypothesis.
Admission control is the process by which a QoS manager accepts or rejects new client connection requests based on the available resources versus the required resources. Admission control is essential in preventing the degradation of quality for currently connected clients.
Admission control delivers a contract to the application guaranteeing:
For each computer:
- cpu time, available at specific interval
- memory
Before admission, it must assess resource requirements and reserve them for the application
Flow specs provide some information for admission control, but not all - assessment procedures are needed as there is an optimisation problem:
- clients don't use all of the resources that they requested
- flow specs may permit a range of qualities
Admission controller must negotiate with applications to produce an acceptable result

21. 3.3 Overall Structure Resource Resource Resource QoS QoS QoS
1: Resources provide flow spec to main QoS manager through local QoS managers
2: Main QoS ready to reserve resources
3: Client send request to main QoS
4: Main QoS decides if client can be served based on available resources
5: If so, main QoS tells local QoS to allocate resources (if not, client is rejected)
6: Service begins
7: Main QoS and local QoS monitor resource usage / quality, adjust allocated resources if necessary
8: Return to step 4 if new client connects
9: Service ends, resources are freed
Resource
Resource
Resource
QoS
QoS
QoS
A distributed multimedia system is a complex series of distinct interactions between clients, quality of service managers, and resource components. At the top of the hierarchy sits the main QoS manager. At each resource component, a local QoS manager exists.
The local QoS managers will gather flow specifications from the particular applications at the resource components, such as video file-servers. These servers will indicate in the flow specification how much bandwidth they will need, what loss rate is acceptable, etc. If the local QoS managers can guarantee these resources will be available, they will forward the details to the main QoS manager, which responds whether it can guarantee all of the needed resources for ready to accept client requests.
When a client makes a request of the system, it goes to the main QoS manager. Notice is sent out to the needed local QoS managers to reserve the resources for their respective components. If all of the resources cannot be reserved for a particular request, the main QoS manager negotiates with the client and with the local QoS managers to see if lower resource requirements can be made. This acceptance/rejection process is referred to as admission control.
If at any time during the client-server interaction the resource components need more resources due to varying conditions, the main and local QoS managers negotiate until an agreement for more resources can be reached.
Another consideration is that whenever there are multiple clients connected to the system, there must be a protocol for determining how they each will be served in relation to the other. This scheduling protocol must be set at both the main and local QoS manager level.
An alternative to this simple scheduling algorithm is a method that gives priority to certain clients. The priority could be based on defined “importance” of the client’s request, or the time in which the client needs the data, or a combination of these factors. The system then assigns the share of the resources based on the priority level.
It should be noted that there are two main types of distributed multimedia systems: Internet-based, and proprietary. Internet-based systems consist of primarily software systems that function as quality of service managers. Proprietary systems, however, can and often do consist of custom hardware, in addition to the software.
Controller
Main QoS
Client
Client
Network Transmission Line

22. 3.4 QoS Summary
Serving multimedia requires strict resource control to maintain quality
Resources consist of bandwidth, latency, and loss rate, among others
Resource components declare the resources they need in flow specifications
Quality of service managers negotiate and reserve resources to guarantee quality
Resource + flow spec + QoS manager + transmission lines = distributed multimedia system
We can see that if we are to expect certain quality levels from the multimedia streams we receive over the Internet, a specialized resource management system must be put in place.
This management system, known as a distributed multimedia system, takes form as the interaction of resource components that know what resources they require and quality of service managers that have the ability to negotiate for and reserve these resources.
This resource reservation process is the core idea behind the guarantee of quality for any given client-server interaction. The reservation process simultaneously satisfies client needs and prevents degradation of service.

23. 4 Resource Management System
Provide the means to offer QoS to multimedia applications
Addressing issues
QoS Calculation
To check whether the QoS demands of an application can be satisfied
Resource Reservation
To reserve an amount of resources according to the given QoS guarantee
Resource Scheduling
To enforce that the given QoS guarantees are satisfied by appropriate scheduling of resource access
Scheduling of resources to meet the existing guarantees:
Fair scheduling: allows all processes some portion of the resources based on fairness:
E.g. round-robin scheduling (equal turns), fair queuing (keep queue lengths equal)
not appropriate for real-time MM because there are deadlines for the delivery of data
Real-time scheduling: traditionally used in special OS for system control applications - e.g. avionics. RT schedulers must ensure that tasks are completed by a scheduled time.
Real-time MM requires real-time scheduling with very frequent deadlines.
Suitable types of scheduling are:
Earliest deadline first (EDF) – Streams are assigned based on timing criteria: the item with the earliest deadline goes first.
Rate-monotonic (RM) – Streams are assigned priorities according to their rate: the higher the rate of work items on a stream, the higher the priority of a stream.

24. 4.1 Resources Resources Resource Capacity
All the entities which participate in the overall task of the application
Classification (active vs. passive; exclusive vs. shared; single vs. multiple)
Scheduled, Assigned for QoS
Resource Capacity
Availability for application when needed
Be at least as large as the requirements for QoS
Depending on the mechanisms for QoS calculation, resource reservation and scheduling
Resources
All the entities which participate in the overall task of the application
Scheduled, Assigned for QoS
Classify
Active vs Passive – ex: CPU vs memory
Exclusive or shared by several processes at a time
Single or multiple
e.g) Bus bandwidth, I/O devices, External storage, Network adapters and network resources, Processors, Main memory
Resource Capacity
Availability for application when needed
Be at least as large as the requirements for QoS
Depending on the mechanisms for QoS calculation, resource reservation and scheduling

25. 4.2 Reservation Policies Pessimistic approach Optimistic approach
The resource capacities are reserved for the worst case
Advantage: avoid conflicts, offer deterministic guarantees
Disadvantage: high cost, underutilization of resources
Optimistic approach
Resources are reserved on average workload
Advantage : cheaper
Disadvantage : temporal resource conflicts
Resource Reservation Protocol (RSVP)
To exchange and negotiate QoS requirements
Receiver-oriented approach. Receivers are responsible for initiating and keeping the reservation active.
Pessimistic approach
advantage: avoids conflicts and offers deterministic guarantees
disadvantage : reserving extensive amounts of capacities for such peak requirements can be rather costly and leads to the underutilization of resources if there is a significant difference between peak and average data rate of a stream.
Optimistic approach
advantage : cheaper than pessimistic
disadvantage : temporal resource conflicts. Therefore application must be aware of them, and must be ready to cope with them.
RSVP
this protocol is to exchange and negotiate QoS requirements across system boundaries.
Depending on the reservation protocol, there are two approaches that is, receiver- oriented or sender-oriented way.
RSPV is receiver-oriented approach. That means receivers are responsible for initiating and keeping the reservation active as long as they want to receive the data.

26. 4.3 Resource Scheduling
Scheduling of resources to meet QoS requirements
Fair scheduling: allow all processes some portion of the resources based on fairness
Real-time scheduling: all to meet real-time requirements (with deadlines)
Regular continuous multimedia streams
Bursty real-time traffic
Scheduling of resources to meet the existing guarantees:
Fair scheduling: allows all processes some portion of the resources based on fairness:
E.g. round-robin scheduling (equal turns), fair queuing (keep queue lengths equal)
not appropriate for real-time MM because there are deadlines for the delivery of data
Real-time scheduling: traditionally used in special OS for system control applications - e.g. avionics. RT schedulers must ensure that tasks are completed by a scheduled time.
Real-time MM requires real-time scheduling with very frequent deadlines.
Suitable types of scheduling are:
Earliest deadline first (EDF) – Streams are assigned based on timing criteria: the item with the earliest deadline goes first.
Rate-monotonic (RM) – Streams are assigned priorities according to their rate: the higher the rate of work items on a stream, the higher the priority of a stream.

27. 4.4 Resource Management Phase
Phase 1: the set-up or QoS negotiation phase
Applications specify their QoS requirements to be used for the admission test and the QoS calculation
Phase 2: the transmission or QoS enforcement phase
Resources are scheduled with respect to the given QoS guarantees.
Schedulers handle time-critical multimedia streams prior to time-independent data
Resource Monitoring
Adaptation
Phase 3
After the transmission has finished, the allocated resources must be released.
Resource monitoring : observe the resource usage of the application, and monitor the overall load put onto the resource.
Adaptation : inform applications that their resource usage must change and that they should renegotiate their resource reservation.

28. 4.5 Resource Management System Structure
Contain components used in the enforcement phase
Consist of System Resource Manager and Resource Managers
System Resource Manager
Control the single ‘Resource Managers’
Resource Manager
Contain algorithms for admission control and policy control
Keep information about the characteristics of the resource and its reservations
CPU resource manager, Memory resource manager and so on
Resource management schemes: static vs. dynamic
The resource management contains components used in the enforcement phase and modules needed in the negotiation phase.
Resource manager
it exists one for one resource.
it contains algorithms for admission control and policy control
admission control is to ensure that sufficient resources are available to handle the data stream and
policy control is to ensure that the particular data stream is permitted to use the resources.
Centralized approach – drawbacks of this approach are that it is not scalable and that it is represents a single point of failure.
Not scalable
Represent single point of failure

29. 4.6 Static Resource Management Scheme
Perform QoS calculation and resource reservation during the setup time
Schedule the resource in such a way that processing deadlines are met
Advantage
Offer strong guarantees for the application’s performance
Provide reliable QoS
Drawback
Difficult to determine the amount of resource needed in advance
Not easily cope with a change in the set of running applications during the run-time of an application
Rely on total knowledge of the set of available resources
Resource management schemes include static ones and dynamic ones.
Static resource management scheme performs QoS calculation and resource reservation during the setup time
It also schedules the resource in such a way that processing deadlines are met
The scheme can provide reliable QoS; that is, all resource requirements of multimedia can be met.
However, there are some drawbacks.

30. 4.7 Dynamic Resource Management Scheme
Renegotiate the resource as changes of requirements at run-time
The goal
Support of variable-bit rate streams
Adaptation to changes in the set of applications to be served
Allowing for a dynamic change in the relative priority of applications
Serving more applications concurrently
Handling of changes in resource availability
Consisting components
Resource monitor
System resource manager: responsible for the negotiations
Dynamic Resource Management Scheme (Adaptive resource management) extend the static approach by methods for resource usage monitoring and renegotiation
Renegotiate the resource as changes of requirements at run-time
The goal
-- Support of variable-bit rate streams which have dynamically varying resource requirements
-- Adaptation to changes in the set of applications to be served
-- Allowing for a dynamic change in the relative priority of applications
-- Serving more applications concurrently as is possible with hard(worst-case assumptions) based QoS provisioning
-- Handling of changes in resource availability
Consisting components
-- Resource monitor
observe the resource usage and overall load of resource
-- System resource manager : responsible for the negotiations
Gather the state information form the resource monitors
Decide which application should adapt its resource usage and to what extent

31. 4.7 Dynamic Resource Management Scheme
Applications
Receive adaptation notifications
Decide how to change their behavior to adapt their resource demands
Monitor the QoS and start a QoS renegotiation
Drawback
Not able to provide guaranteed, constant QoS
Applications of dynamic resource management scheme include:
Receive adaptation notifications
Decide how to change their behavior to adapt their resource demands
Monitor the QoS and start a QoS renegotiation
Drawback:
Not able to provide guaranteed, constant QoS

32. 5 Stream Adaptation: Scaling
Scaling reduces flow rate at source
Temporal scaling: skip frames or audio samples
Spatial scaling: reduce frame size or audio sample quality
Frequency scaling: modify image compression algorithm without much loss of quality.
Color-space scaling: reduce the number of entries in color space.
Scaling reduces flow rate at source
temporal: skip frames or audio samples
spatial: reduce frame size or audio sample quality
Filtering reduces flow at intermediate points
RSVP is a QoS negotiation protocol that negotiates the rate at each intermediate node, working from targets to the source.

33. 5 Stream Adaptation: Filtering
Filtering reduces flow at intermediate points
Filtering provides best possible QoS to each target by applying scaling at each relevant node on the path from the source to the target.
RSVP is a QoS negotiation protocol that negotiates the rate at each intermediate node, working from targets to the source.
Scaling reduces flow rate at source
temporal: skip frames or audio samples
spatial: reduce frame size or audio sample quality
Filtering reduces flow at intermediate points
RSVP is a QoS negotiation protocol that negotiates the rate at each intermediate node, working from targets to the source.

34. 5 Stream Adaptation: Filtering
Source
Targets
High
bandwidth
Medium
Low
Scaling reduces flow rate at source
temporal: skip frames or audio samples
spatial: reduce frame size or audio sample quality
Filtering reduces flow at intermediate points
RSVP is a QoS negotiation protocol that negotiates the rate at each intermediate node, working from targets to the source.

35. 5.1 A Sample Wavelet Video Filtering
Basic Concept:
Basic Concept:
The frame is encoded to packets with “priority label”.
In case of insufficient bandwidth, drop the least important packets to maximize the visual quality.

36. 5.1 Wavelet Video Filtering
Video frames are encoded into packets with “priority label”
QoS Filter drops the least important packets in case of insufficient bandwidth
This maximizes visual quality with resource constraints
Video frames are encoded into packets with “priority label”
QoS Filter drops the least important packets in case of insufficient bandwidth
This maximizes visual quality with resource constraints

37. 6 Summary
Multimedia applications and systems require new system mechanisms to handle large volumes of time-dependent data in real time (media streams).
The most important mechanism is QoS management, which includes resource negotiation, admission control, resource reservation and resource management.
Negotiation and admission control ensure that resources are not over-allocated, resource management ensures that admitted tasks receive the resources they were allocated.
Read textbook Chapter 20.
The contents of this lecture is from textbook Chapter 20.