The Advantages of a Video Conferencing System

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Petri Vuorimaa 1

Video conferencing

• Introduction • Standards • Products • Internet telephony

• Computer Telephony Integration (CTI)

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)

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

Equipment

Video/audio capture Modem, ISDN or LAN Audio card Communication network

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

Multipoint Conferences

Communications network

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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)

Standard families (cont.)

H.320 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

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

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

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

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

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

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

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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Protocol stack

T.120

• Implements the extra services:

+ conformance + image transfer + shared workspaces + file transfer + multipoint conferences Petri Vuorimaa 27

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 Petri Vuorimaa 28

Transport layer

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

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

Video networks

• Best possible image quality • Intended primarily for conferences • Uses either ISDN or ATM network

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

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)

Gatekeepers

• Required by H.323 standard family

• For example, Intel LANDesk Conferencing Manager

+ automatic gate keeper + zone management

+ outbound route management + incoming call routing

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

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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

Internet telephony (cont.)

• Some long distance operators use Internet connections for telephony

• Allows the use of compression • For example, 64 Kbps -> 2.4 Kbps

Calls within organization

Public Internet calls

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

CTI block diagram

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)

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)

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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Integrated system

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

PC cards

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

CTI APIs (cont.)

• SCSA framework

• Sun Java Telephony API = JTAPI

+ Java-framework