Video conferencing. Introduction Standards Products Internet telephony Computer Telephony Integration (CTI) Petri Vuorimaa 1

Transcription

1 Video conferencing Introduction Standards Products Internet telephony Computer Telephony Integration (CTI) Petri Vuorimaa 1

2 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) Petri Vuorimaa 2

3 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 Petri Vuorimaa 3

4 Equipment Video/audio capture Modem, ISDN or LAN Communication network Audio card Petri Vuorimaa 4

5 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 Petri Vuorimaa 5

6 Multipoint Conferences Communications network Multipoint server Petri Vuorimaa 6

7 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) Petri Vuorimaa 7

8 Standard families (cont.) Petri Vuorimaa 8

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10 H.320 Petri Vuorimaa 10

11 Video Two resolutions: + Quarter Common Intermediate Format (QCIF): 176 x 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 Petri Vuorimaa 11

12 Audio codecs Three different audio codecs: + G Kbps narrow band + G Kbps wide band + G Kbps narrow band Petri Vuorimaa 12

13 Different classes Petri Vuorimaa 13

14 H.324 Petri Vuorimaa 14

15 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 audio codec transmits at 5.3 or 6.3 Kbps Petri Vuorimaa 15

16 H.324 (cont.) Can use even 28.8 and 33.3 Kbps modems (V.34) Codecs are better, but quality is worse than H H.320 has much more bandwidth than H.324 Petri Vuorimaa 16

17 H.323 Petri Vuorimaa 17

18 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) Petri Vuorimaa 18

19 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 Petri Vuorimaa 19

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21 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 Petri Vuorimaa 21

22 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 Petri Vuorimaa 22

23 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 Petri Vuorimaa 23

24 Different alternatives Petri Vuorimaa 24

25 Protocol stack Petri Vuorimaa 25

26 T.120 Implements the extra services: + conformance + image transfer + shared workspaces + file transfer + multipoint conferences Petri Vuorimaa 26

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 27

28 Transport layer Petri Vuorimaa 28

29 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 Petri Vuorimaa 29

30 Products Video conference bridges Video networks Video conference rooms Workstations Gatekeepers Gateways Petri Vuorimaa 30

31 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 Petri Vuorimaa 31

32 Video networks Best possible image quality Intended primarily for conferences Uses either ISDN or ATM network Petri Vuorimaa 32

33 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 Petri Vuorimaa 33

34 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) Petri Vuorimaa 34

35 Gatekeepers Required by H.323 standard family For example, Intel LANDesk Conferencing Manager + automatic gate keeper + zone management + outbound route management + incoming call routing Petri Vuorimaa 35

36 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 Petri Vuorimaa 36

37 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 Petri Vuorimaa 37

38 Internet telephony (cont.) Petri Vuorimaa 38

39 Internet telephony (cont.) Some long distance operators use Internet connections for telephony Allows the use of compression For example, 64 Kbps -> 2.4 Kbps Petri Vuorimaa 39

40 Calls within organization Petri Vuorimaa 40

41 Public Internet calls Petri Vuorimaa 41

42 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 Petri Vuorimaa 42

43 CTI Computer Telephony Integration (CTI) integrated computers and telephones Brings savings and increases efficiency (invest return time usually under year) Several different implementations Petri Vuorimaa 43

44 CTI block diagram Petri Vuorimaa 44

45 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) Petri Vuorimaa 45

46 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) Petri Vuorimaa 46

47 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 Petri Vuorimaa 47

48 Call Center Petri Vuorimaa 48

49 Integrated system Petri Vuorimaa 49

50 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 Petri Vuorimaa 50

51 PC cards Petri Vuorimaa 51

52 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 Petri Vuorimaa 52

53 CTI APIs (cont.) SCSA framework Sun Java Telephony API = JTAPI + Java-framework + utilizes above mentioned API definitions Petri Vuorimaa 53