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Video conferencing
• Introduction• Standards• Products• Internet telephony• Computer Telephony Integration (CTI)
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Introduction
• Video conferencing can be used for+ Audio-visual communication+ Sharing of documents, tables, pictures, etc.
• Several benefits+ Traveling costs+ Response time+ Better understanding (body language)
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Systems
• Two main types:+ Video conferencing rooms+ Video conferencing software
• Video conferencing rooms are for group meetings+ Organization either has it own premises or rents them
from operator
• Video conferencing software is for personal use
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Equipment
Video/audiocapture
Modem, ISDNor LAN
Audiocard
Communicationnetwork
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Group Meetings
• Two types of video conferences:+ Point-to-point conferences (video telephony)+ Multipoint conferences (group meetings)
• In group meetings, there are two ways to share turns (i.e., floor control):+ Automatic selection (e.g., based on audio)+ Chairman
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Multipoint Conferences
Communicationsnetwork
Multipoint server
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Standard Families
• Integrated Services Digital Network - ISDN (H.320)
• Networks supporting QoS (H.310, H.321, and H.322)
• Local area networks - LAN (H.323)• Plain old telephone systems - POTS (H.324)• Shared workspaces (T.120)
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Standard families (cont.)
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H.320
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Video
• Two resolutions:+ Quarter Common Intermediate Format (QCIF): 176 x
144+ Common Intermediate Format (CIF): 352 x 288
• Frame rates 7.5, 10, 15, or 30 frames per second• Motion estimation can be used, but is not
necessary
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Audio codecs
• Three different audio codecs:+ G.711 48-64 Kbps narrow band+ G.722 48-64 Kbps wide band+ G.728 16 Kbps narrow band
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Different classes
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H.324
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H.324
• Meant for Plain Old Telephone Systems (POTS)• H.263 can be used for below 64 Kbps video
coding+ sub-QCIF (128 x 96), QCIF (176 x 144), CIF (352 x
288), 4CIF (702 x 576), and 16CIF (1408 x 1152)
• G.723.1 audio codec transmits at 5.3 or 6.3 Kbps
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H.324 (cont.)
• Can use even 28.8 and 33.3 Kbps modems (V.34)• Codecs are better, but quality is worse than H.320
+ H.320 has much more bandwidth than H.324
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H.323
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H.323
• LANs (Internet & Intranet) without QoS support• Clients, multipoint servers, gateways and
gatekeepers• Real-time transport protocol (RTP)• New audio codec G.729 (8 Kbps)
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Gateway
• The gateway allows the integration of H.323 networks with other networks
• Tasks:+ transformations between media formats+ transformations between communication protocols+ transformations between audio and video codecs+ connection setup and tear-down
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Gatekeeper
• Gatekeeper takes care of resource reservations• The amount of simultaneous users can be limited• Transforms connection requests from outside to
internal addresses and vice versa
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Multipoint Server
• Required when three or more clients participate the conference
• Is composed of two parts:+ Multipoint Controller takes care of connections+ Multipoint Processor(s) transform(s) media streams
• Processors can also combine streams:+ Mixing+ Switching
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Multipoint Server (cont.)
• Videoconferences can be set up in three different ways:+ unicast, multicast, and broadcast
• Three ways of practical implementation:+ centralized, distributed, and hybrid
• In practice H.323 is implemented on top of IP etc. protocols
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Different alternatives
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Protocol stack
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T.120
• Implements the extra services:+ conformance+ image transfer+ shared workspaces+ file transfer+ multipoint conferences
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T.120 (cont.)
• T.120 is composed of three layers:+ transport layer+ protocol layer+ application layer
• Transport layer is divided into three levels:+ transport protocol+ multipoint conference+ conference control
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Transport layer
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T.120 (cont.)
• Protocol layer is composed of+ image transfer (T.126)+ binary file transfer (T.127)+ share application transfer (T.Share)+ resource reservation (T.RES)
• New standard family T.130 is under development
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Products
• Video conference bridges• Video networks• Video conference rooms• Workstations• Gatekeepers• Gateways
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Video conference bridges
• Support primarily H.320 and T.120 standard families
• Allow multipoint video conferencing• Support few tens of users• Participants either call to the bridge or the bridge
setups the connections itself
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Video networks
• Best possible image quality• Intended primarily for conferences• Uses either ISDN or ATM network
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Video conference rooms
• Intended for video conferencing• Maintained by companies or operators• Based on H.320 (ISDN) standard family• H.323 (Internet) standard family is coming
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Workstations
• LAN, ISDN, or modem card• Audio and video cards• Software (e.g., Microsoft Netmeeting, Picturetel,
Intel)• H.320 most common, but H.323 is coming (client
software is available)
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Gatekeepers
• Required by H.323 standard family• For example, Intel LANDesk Conferencing
Manager+ automatic gate keeper+ zone management+ outbound route management+ incoming call routing
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Gateways
• Intel LiveGateway+ bi-directional connection between H.323 and H.320
systems+ format transform between H.323 and H.320 systems+ supports also H.320 multipoint server+ four gates in on PC+ either local or gate keeper based administration
• Both Intel LANDesk Conferencing and LiveGateway are Windows NT based
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Internet telephony
• With suitable hardware and software computers connected to Internet can be used for telephony
• No extra charges, but the quality is not very good• Gateways to ordinary telephone network also
available
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Internet telephony (cont.)
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Internet telephony (cont.)
• Some long distance operators use Internet connections for telephony
• Allows the use of compression• For example, 64 Kbps -> 2.4 Kbps
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Calls within organization
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Public Internet calls
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Internet telephony products
• Microsoft Netmeeting supports H.323 and T.120 standard families
• Includes H.263 video codec• Compatible with Intel and PictureTel products• Utilizes Intel Pentium MMX technology• Other products include White Pine Software CU-
SeeMe, IBM Internet Connection Phone, VDOnet VDOPhone
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CTI
• Computer Telephony Integration (CTI) integrated computers and telephones
• Brings savings and increases efficiency (invest return time usually under year)
• Several different implementations
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CTI block diagram
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CTI applications
• Voice mail (answering service)• Automatic call transfer• Intelligent call routing and distribution (call
centers)• Voice text (timetable, etc.)• Fax requests (information delivered via fax)
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CTI applications (cont.)
• Interactive telephone services (reservations, orders, etc.)
• Call records (automatic recognition of customers)• Gateways (video conference with standard
telephone)• Call management (automatic dialing)
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CTI implementations
• CTI can be based on separate server• Another alternative is to join telephone directly to
workstation• Video conference, Internet telephony, and CTI
systems can be integrated
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Call Center
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Integrated system
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CTI standards
• Multi-Vendor Integration Protocol (MVIP)• System Computing System Architecture (SCSA)• Both are buses connecting different PC cards• Buses are used for call traffic within PC
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PC cards
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CTI APIs
• Microsoft Telephony Application Programming Interface = TAPI (-93)+ Windows applications
• Novell Telephony Service API = TSAPI (-93)+ Novell servers
• IBM CTI API+ Switches and their interfaces
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CTI APIs (cont.)
• SCSA framework• Sun Java Telephony API = JTAPI
+ Java-framework+ utilizes above mentioned API definitions