Video conferencing Introduction Standards Products Internet telephony Computer Telephony Integration (CTI) 1
Introduction Video conferencing can be used for Several benefits Audio-visual communication Sharing of documents, tables, pictures, etc. Traveling costs Response time Better understanding (body language) 2
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 3
Equipment Video/audio capture Modem, ISDN or LAN Communication network Audio card 4
Group Meetings Two types of video conferences: In group meetings, there are two ways to share turns (i.e., floor control): Point-to-point conferences (video telephony) Multipoint conferences (group meetings) Automatic selection (e.g., based on audio) Chairman 5
Multipoint Conferences Communications network Multipoint server 6
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) 7
Standard families (cont.) 8
9
H.320 10
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 11
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 12
Different classes 13
H.324 14
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 15
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 16
H.323 17
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) 18
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 19
20
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 21
Multipoint Server Required when three or more clients participate the conference Is composed of two parts: Processors can also combine streams: Multipoint Controller takes care of connections Multipoint Processor(s) transform(s) media streams Mixing Switching 22
Multipoint Server (cont.) Videoconferences can be set up in three different ways: Three ways of practical implementation: unicast, multicast, and broadcast centralized, distributed, and hybrid In practice H.323 is implemented on top of IP etc. protocols 23
Different alternatives 24
Protocol stack 25
T.120 Implements the extra services: conformance image transfer shared workspaces file transfer multipoint conferences 26
T.120 (cont.) T.120 is composed of three layers: Transport layer is divided into three levels: transport layer protocol layer application layer transport protocol multipoint conference conference control 27
Transport layer 28
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 29
Products Video conference bridges Video networks Video conference rooms Workstations Gatekeepers Gateways 30
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 31
Video networks Best possible image quality Intended primarily for conferences Uses either ISDN or ATM network 32
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 33
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) 34
Gatekeepers Required by H.323 standard family For example, Intel LANDesk Conferencing Manager automatic gate keeper zone management outbound route management incoming call routing 35
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 36
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 37
Internet telephony (cont.) 38
Internet telephony (cont.) Some long distance operators use Internet connections for telephony Allows the use of compression For example, 64 Kbps -> 2.4 Kbps 39
Calls within organization 40
Public Internet calls 41
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 CUSeeMe, IBM Internet Connection Phone, VDOnet VDOPhone 42
CTI Computer Telephony Integration (CTI) integrated computers and telephones Brings savings and increases efficiency (invest return time usually under year) Several different implementations 43
CTI block diagram 44
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) 45
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) 46
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 47
Call Center 48
Integrated system 49
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 50
PC cards 51
CTI APIs Microsoft Telephony Application Programming Interface = TAPI (-93) Novell Telephony Service API = TSAPI (-93) Novell servers IBM CTI API Windows applications Switches and their interfaces 52
CTI APIs (cont.) SCSA framework Sun Java Telephony API = JTAPI Java-framework utilizes above mentioned API definitions 53