1. Distributed multimedia systems involve streaming continuous media like audio and variable bit rate video, as well as block-mode media like images and text. 2. Communication modes for transmitting information streams include uni-directional, half-duplex, full-duplex, broadcast, and multicast, which can be symmetric, asymmetric, or involve a single source. 3. Quality of service parameters that determine the suitability of a network channel for an application include bit rate, error rate, delay, packet size and rate, and jitter for both circuit-switched and packet-switched networks.

1. Information and Communication
Technologies(ICT)
Principles and Perspectives
Lecture : Distributed multimedia systems
Halsall, F. Multimedia Communication (1.5)

3. Media types
• Continuous ( Streaming)
• Constant Bit Rate ( CBR)
• Audio Streaming
• Variable Bit Rate ( VBR)
• Video streaming ( After compression amount of information associated with each frame varies. Information
stream generated after fixed time intervals but bit rate is variable
• Block-mode media
• Information comprises a single block of information created in time-independent way
• Image, text (downloading)

4. Communication modes
• Transfer of information streams associated with an application can take
place in following 5 modes
1. Uni-directional
2. Both directions alternatively
3. Both directions simultaneously
4. Single source, received by all other nodes
5. Single source, a subset of nodes

6. Communication modes
• Simplex : Photographic image from deep-space probe after regular time interval
• Half-duplex: Requesting data from server
• Full-duplex: digitized speed, video conferencing
• Broadcast: TV, Radio
• Multicast: similar to broadcast but information received by specific subset of the
nodes connected to network. Video conferencing involving predefined group of
terminals

7. Communication modes
• Symmetric: information flow and bit rate is equal in both directions.
Telephone call
• Asymmetric: request to web server from browser . Low bit rate from
browser to server, higher from other end

8. Communication Channels
• Time dependent way known as Circuit mode (synchronous channel,
constant bit rate)
• Time varying way known as packet mode (asynchronous channel, variable
bit rate)

9. Circuit Mode
• Interconnected set of switching
offices/exchanges.
• Examples are PSTN (public
switched telephone network)
• ISDN(Integrated Services Digital
Network). Digital
• Signaling messages for setting up
and clearing connections

10. Packet Mode
• Connection oriented
• Connection less

11. Network QoS
• Operational parameter associated with a communication channel through
network known as QoS parameters. They determine suitability of a channel
for a particular application
• Circuit Switched network
• The bit rate
• The mean bit error rate (BER) ( the probability of a bit corrupted in transmission)
• The transmission delay

12. Network QoS
• Packet Switched network
• Max packet size
• Mean packet transfer rate ( avg no of packets per second)
• Mean packet error rate ( probability of received packet containing error)
• Mean packet transfer delay (store and forward delay)
• Worst-case jitter
• Transmission delay ( bit rate, network delay, codec delay)

13. Application QoS
• Application depending upon the type of media involves have Qos parameters
• For images transfer need minimum image resolution and size
• For video digitization format, refresh rate
• Required bit rate or mean packet transfer rate
• Max startup delay
• Max end to end delay
• Max delay variation/jitter
• Max round trip delay