Prof. Pallapa Venkataram, Electrical Communication Engineering, Indian Institute of Science, Bangalore – 560012, India Multimedia Communications
Objectives To know the networking evolution. To understand the network types. To discuss multimedia requirements in the communication systems. To understand the basics of a multimedia communication system. To illustrate multimedia networks. To know the Internet protocol suite for multimedia communications.
Networking Infrastructure Evolution Network deployment issues
Network Topologies Evolution LAN Linear topology Star-wired Multisegment Backbone-connected Switched-backbonet WLAN WAN
Multimedia Requirements To develop schemes for multi-access networks which can provide performance guarantees. To develop a distribute route-selection strategy for point-to-point networks. Real-time multimedia applications require guaranteed performance communication services, such as throughput, delay, delay jitter and loss rate. The characteristics of a source, such as peak and average rate, are known at channel establishment time. Channel parameters have to be predicted in live continuous video sources.
Communication Service for Multimedia Quality-of-service (QoS) support and group communication system: establishment and take-down of appropriately congured channels; negotiation of QOS levels between end-systems, intermediate systems, and network control; and control of the agreed QOS level bandwidth, delay, delay jitter (variance), and reliability. Audio/Video groups can: have static or dynamic memberships during their lifetime, have centrally (typically sender) or distributedly (typically receiver) controlled membership, consist of members with homogeneous or be heterogeneous characteristics and requirements.
Multimedia Communication System Communication system - A system or facility capable of providing information transfer between persons and equipment. CD-ROM: “Compact disk read-only memory.” Client-Server Model: A client makes a request and a server fulfills that request. Composite Video: Analog video signals can be broken down into parts such as luminance (Black & White) and chrominance (color).
Multimedia File types Here are some examples of le types: Text Files: .txt, .doc, .rtf Audio Files: .au, .aif, .wav Graphic files: .jpg, .gif, .tif, .bmp, .pict, .pcx Moving video files: .qt, .mov, .avi Animation: .fli, .flc
Multimedia Communication System Interactive Multimedia Design Interlacing Interleaved Linear Multimedia Non-Interactive Multimedia Nonlinear Multimedia Presentation Multimedia Latency and Bandwidth
Multimedia Communication System LAN Access Method Routing Frame and Packet Structures Packet Discrimination Identify packets that require special handling. Be capable of accommodating those special requirements. Bandwidth Requirement, Reservation and Conservation High bandwidth and low latency
Multimedia Communication System Architecture The ability to manage dynamically the achieved QoS of each service component The possibility for users to select some resources that best meet their needs. The possibility to interact with another user whose equipment has differing characteristics. The communications network must allow any user to select the service components he/she wants: The possibility for users to join in or withdraw from a communication session according to certain policies, such as agreement of all interacting partners before admitting a new user. The possibility to set such quality of service parameters as the synchronization tolerance between the service components, the echo sensitivity, the burst sensitivity, and so on.
Multimedia Networks Technical Issues Admission control Scheduling Resource management Congestion control Policing/Shaping
Multimedia Hardware/Software Audio/Video Hardware Digital Video (DV) Analog to Digital devices Built-in Hardware Digital Video Software Multimedia Software
Multimedia Internet Protocols Multimedia over TCP Multimedia over UDP
RTP Real-time Transport Protocol (RTP) provides support for the transport of real-time data such as video and audio streams. RTP needs support from lower layers that actually have control over resources in switches and routers RTP/RTCP provides functionality and control mechanisms necessary for carrying real-time content. RTP/RTCP itself is not responsible for the higher-level tasks like assembly and synchronization. These have to be done at application level.
RTCP Real-Time Control Protocol extends RTP In an RTP session, participants periodically send RTCP packets to convey feedback on quality of data delivery and information of membership. Packets defined for carrying control information: SR: Sender report, for transmission and reception statistics from session participants that are active senders. RR: Receiver report, for reception statistics from session participants, that are not active senders. SDES: Source description items, including CNAME BYE: Indicates end of participation APP: Application specific functions
Multimedia Internet Protocols SAP & SDP Peer to peer communication, the concept of session. SIP Signaling mechanisms that are necessary to establish a session and to negotiate the parameters to be used in it, such as codecs, media, location, etc. MBONE Tools SDR, VIC, VAT and RAT, WB, NTE.
Multimedia Internet Protocols RSVP Network control protocol Allows data receiver to request a special end-to-end quality of service for its data flows. RTSP A client-server multimedia presentation protocol to enable controlled delivery of streamed multimedia data over IP network. Aims to provide the same services on streamed audio and video just as HTTP does for text and graphics.
Multimedia Communications High-Density File Transfers Graphics File Transfers Audio File Transfers Video File Transfers Audio Communication Computer-Based Telephony Computer-Based Audio Conferencing Streaming Audio Video Communication Video Conferencing Streaming Video