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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