UoA/CNL TNC 2000 Potential and Limitations of a Teleteaching Environment based on H.323 Audio-Visual Communication Systems. P. Balaouras, I. Stavrakakis, L. Merakos Communication Networks Laboratory (CNL) University of Athens (UoA)

UoA/CNL TNC 2000 Introduction Teleteaching services Networked multimedia applications – MJPEG/ATM – Mbone tools  medium quality, desktop – H.323 systems  classroom settings H.323 are mature for videoconferencing; what about teleteaching (TT) ? TT requir. are a superset of VC requir.

UoA/CNL TNC 2000 Outline Introduction The ITU-T H.323 Recommendations Capabilities of present H.323 products Teleteaching Environment Functional requirements Conclusions

UoA/CNL TNC 2000 The ITU-T H.323 Recommendations H.323 entities Capabilities of H.323 terminals –audio, video, data exchanging and processing –controls issues and device control H.323 Multipoint Conferences Capabilities of the H.323 MCU Control issues

UoA/CNL TNC 2000 H.323 Entities H.323 terminal H.323 Multipoint Control Unit end-points H.323/H.32* Gateway H.323 Gatekeeper

UoA/CNL TNC 2000 Defined audio capabilities of H.323 terminals H.323 terminal Audio codec(s) Audio channel(s) G.711 A-law, μ-law G.722, G.723, G.728, G.729, MPEG-1 audio Coding schemes Green for mandatory features Orange for optional features H.323 terminal Audio mixing multicast G.729 G.728 Assymetric operation

UoA/CNL TNC 2000 Defined visual capabilities of H.323 terminals H.323 terminal Video codec(s) Video channel(s) H.261 QCIF H.261 CIF, H.263 SQCIF,QCIF, CIF, CIF, 4CIF, 16CIF Coding schemes Green for mandatory features Orange for optional features H.323 terminal Video mixing or switching multicast QCIF CIF Assymetric operation

UoA/CNL TNC 2000 Defined data capabilities of H.323 terminals H.323 terminal T.120 entity Data channel(s) T.120 Green for mandatory features Orange for optional features H.323 terminal - One or more data channel(s) - Unidirectional or bi-directional channel(s)

UoA/CNL TNC 2000 Audio-visual capabilities of H.323 terminals

UoA/CNL TNC 2000 Capability set (CS) of an H.323 terminal H.245 procedure to exchange CS Decoder capability set –video & audio bit rate, –video, audio format, –algorithm options accepted by decoder Number of simultaneous audio, video decoding Encoder: is free to transmit anything in the agreed set.

UoA/CNL TNC 2000 H.323 Multipoint Conferences Multipoint Controller (MC) –control functions (e.g., chair control) –controls MP Multipoint Processor (MP) –video switching, mixing, transcoding –audio mixing, transcoding –T.120 data distribution

UoA/CNL TNC 2000 Types of multipoint conferences Centralized Decentralized Hybrid

UoA/CNL TNC 2000 Centralized multipoint conferences unicast MCU MP MCU H.323 terminal MCU MP MPMP MPMP MPMP MCMC MCMC MCMC Audio & Video unicasting Audio & Video unicasting Audio & Video multicasting

UoA/CNL TNC 2000 Decentralized multipoint conferences Audio & Video Multicasting MP MP MP MP MC GW H.323 terminal MCU MCMC MCMC - 1 every H.323 terminal - 1 any H.323 end-point IP

UoA/CNL TNC 2000 Hybrid multipoint, centralized audio Video Multicasting MP MP MP MP H.323 terminal MCU - 1 MP for every terminal - 1 MCU IP Audio unicasting MCMC

UoA/CNL TNC 2000 Hybrid multipoint, centralized video Audio Multicasting MP MP MP MP H.323 terminal MCU - 1 MP for every terminal - 1 MCU IP Video unicasting MCMC

UoA/CNL TNC 2000 Characteristics and potential location of MC and MP

UoA/CNL TNC 2000 Defined capabilities of the H.323 MCU Must Support centralized Mult. conferences MP –video switching, –synchronization and video mixing –synchronization and audio mixing, – transcoding, –T.120 data distribution MC –control functions MCMC MCU MPMP

UoA/CNL TNC 2000 MP functions sw Sa Video/audio switching function Sb mix Audio/video mixing function Sa Sb Sd Sc Mixed(Sa,Sb,Sc,Sd) Sd Sc Waste of bandwidth

UoA/CNL TNC 2000 MP functions sw Da Data distribution function Audio/video transcoding function trans Sa QCIF Sb CIF QCIF CIF

UoA/CNL TNC 2000 Control issues performed by MC (H.243 Control issues performed by MC (H.243) Automatic video selection mode Chair-control mode –video broadcast visualization forcing capability –multipoint visualization –video selection Any terminal can have the chair token Floor control - only in chair-control mode Camera control

UoA/CNL TNC 2000 sw Sa Sb Sd Sc Automatic video switching mode Automatic video switching mode The selection mechanism is voice-activated

UoA/CNL TNC 2000 CC - Video broadcast (VCB) To determine which one of the available video streams will be transmitted to all terminals, except chairman’s Sa Sb Sd Sc MCU VCB Sb Sb MCMC MPMP Chair-control terminal

UoA/CNL TNC 2000 CC - Video select (VCS) To determine which video stream will be transmitted to chairman’s terminal Sa Sb Sd Sc MCU VCS Sc Sc MCMC MPMP

UoA/CNL TNC 2000 CC - Multipoint visualization (MCV) To broadcast chairman’s terminal video to all participants Sa Sb Sd Sc MCU MCV Sa MCMC MPMP

UoA/CNL TNC 2000 Floor Control issues performed by MC Floor control is possible only in chair-control mode. Any terminal may request the floor by sending command TIF to the MCU. The MCU forwards the request to the chair-control terminal. MCU TIF MCMC

UoA/CNL TNC 2000 Camera control (H.281) A moderator is able to control the local and remote cameras that are connected to an H.323 terminal that supports H.281 standard (FECC: Far-End Camera Control)

UoA/CNL TNC 2000 Capabilities of present H.323 terminals

UoA/CNL TNC 2000 Teleteaching Environment (TE) An TE enables synchronous participation in a lecture of dispersed set of students located at workspaces. The supported interaction among the workspaces constitute a teleteaching scenario. Set of interactions supported by present H.323 products  potential teleteaching scenario.

UoA/CNL TNC 2000 Available sources as teaching material Teaching media Input Devices Students’ voice Instructor’svoice Tape/CD player Source analog audio signals Students’ mic Instructor’s wireless mic Music, sounds, recorded courses Sa Ia Ma

UoA/CNL TNC 2000 Real object Visual Presenter Camera for Instructor Camera for students Instructor Student(s) VCR Video recorded material Source analog video signals V Iv Sv Mv Available sources as teaching material Teaching media Input Devices

UoA/CNL TNC 2000 Computer System digital streams of data, video and audio files Still media for presentations and docs Continuous audio and video media Applications Broadcast application Appl.Sharing S/W Dp Dv Da Available sources as teaching material Teaching media Input Devices

UoA/CNL TNC 2000 Required H.323 entities IP H.323 & T.120 Multipoint Conference Unit (MCU) H.323 Terminal H.323/H.320 Gateway ISDN H.323 Gatekeeper H.323 Terminal H.323 Terminal H.320 Terminal H.323 Terminal Wz Wy Wx Wi

UoA/CNL TNC 2000 Number of H.323 terminals Multiple audio and video streams are to transmitted  multiple H.323 terminals H.323 terminal(s) Camera for Instructor Camera for students Iv Sv H.323 terminal(s) Camera for Instructor Camera for students Iv Sv H.323 room terminal Video matrix

UoA/CNL TNC 2000 Potential interactions among workspaces A utomatic video switching mode Wi Wx Wy Wz sw mix Ia(Wi) Sa(Wz) Sa(Wx) Sa(Wy) MixedA mixedA MixedA Sa(Wi) mixedA MCU

UoA/CNL TNC 2000 Potential interactions among workspaces Chair control mode Wi Wx Wy Wz sw Ia(Wi) Sa(Wz) Sa(Wx) Sa(Wy) Sel-A Sa(Wi) Sel-A MCU

UoA/CNL TNC 2000 Potential interactions among workspaces Wi Wx Wy Wz mix sw Iv/V(Wi) Sv(Wz) Sv(Wx) Sv(Wy) Sel-V Sel-V* Sel-V Sv(Wi) Sel-V MCU Sel-V: one of Iv/V(Wi),Sv(W*), selected by chair control or automatic video switching * : if Wy is the source then a stream other than Sv(Wy):=Sel-V is transmitted to Wy

UoA/CNL TNC 2000 Potential interactions among workspaces Wi Wx Wy Wz mix sw Dp(Wi) MCU Dp(Wi)

UoA/CNL TNC 2000 Summary of potential interactions Iv/V(Wi) or /Sv* Dp(Wi) Wi Wx Wy Wz Dp(Wi) sw Iv/V(Wi) Sv(Wy) Sv(Wz) Sv(Wx) Dp(Wi) mix Sv(Wi) Ia(Wi) Sa(Wz) Sa(Wx) Sa(Wy) Sel-A Sa(Wi) Sel-A Sel-V MCU Sel-V

UoA/CNL TNC 2000 Teleteaching functional requirements Presentation of a set of TT requirements. In which degree these requirements are fulfilled by present H.323 products. Possible solutions are proposed for requirements that are partly or not fulfilled.

UoA/CNL TNC 2000 Lecture delivery phase requirements R1a: high quality audio-visual communication –Audio:G.711 audio 64 kbps –Video: H.263 CIF bite rate > 768 kbps R1b: R1b: one way lecture delivery without any interference –Use of terminals and MCU that support chair control feature. –In automatic video switching, interference is possible.

UoA/CNL TNC 2000 Lecture delivery phase requirements Wi Wx Wy Wz sw Iv/V(Wi) Sel-V Iv/V(Wi) MCU Ia(Wi) Dp(Wi) - G.711 audio 64 kbps - H.263 CIF bite rate > 768 kbps - Terminals and MCU that support chair control.

UoA/CNL TNC 2000 Lecture delivery phase requirements R2: R2: Presentation of Iv(Wi) and Dp(Wi) in separate display device (i.e., projector) 1 H.323, T.120, PIP Iv(Wi) Dp(Wi) 1 H T.120 Iv(Wi) Dp(Wi ) 1 H.323 & T.120, dual monitor PC with dual VGA output card

UoA/CNL TNC 2000 Lecture delivery phase requirements R3: R3: Instructor should be free to move around as in a conventional classrooms –Wireless microphone. –Pan-Tilt-Zoom camera with auto-tracking feature.

UoA/CNL TNC 2000 R4,R5 - Instructor’s interaction with students R4: R4: Interaction with local or remote students. All participants should be able to listen and watch the speaker. R5: R5: How a student request the floor to ask a question.

UoA/CNL TNC 2000 Chair control Wi Wx Wy Wz sw Iv/V(Wi) MCU Ia(Wi) Dp(Wi) The operator of the chair-control capable terminal shall request the floor on behalf of a student. Complementary floor control system: terminals, camera and MIC

UoA/CNL TNC 2000 Chair control Wi Wx Wy Wz sw Iv/V(Wi) Sa(Wy) Sv(Wy) MCU Ia(Wi) Sa(Wy) Dp(Wi) Sv(Wy) Sa(Wy)

UoA/CNL TNC 2000 Automatic video switching Wi Wx Wy Wz sw Iv/V(Wi) Sa(Wy) Sv(Wy) MCU Ia(Wi) MixedA Dp(Wi) Iv(Wi) or Sv(Wy) Sv(Wy) Sa(Wy) Mixed(Ia(Wi),Sa(Wy) Iv(Wi) or Sv(Wy) Social rules e.g. hand raising are used.

UoA/CNL TNC 2000 R6 - Open conversation R6: Open conversation among all the participants Microphone system in open mode MCU on automatic video selection mode –audio mixing –selection of the video stream of the participant who talks more than two seconds

UoA/CNL TNC 2000 R7 - Interference of an external person IP H.323 & T.120 Multipoint Conference Unit (MCU) H.323 Terminal H.323/H.320 Gateway ISDN H.323 Gatekeeper H.323 Terminal H.323 Terminal H.320 Terminal H.323 Terminal Wz Wy Wx Wi … just as an another workspace H.323 Terminal

UoA/CNL TNC 2000 R8 - Projection of the remote workspace’s signals Permanent display mode on dedicated display device(s) Periodic display mode, on the same device(s) Instant display mode, on the same device(s) One remote workspace each time or panorama R8: R8: Students should be able to attend the reactions and gestures of remote students. This helps in avoiding the sensory deprivation.

UoA/CNL TNC 2000 R8 - Projection of the remote workspace’s signals Presently, Presently, only periodic or instant display can be implemented by using the chair-control capability. Permanent display an be implemented by using other technology such as MBONE tools in parallel to H.323 terminals. No simultaneous view of instructor’s video and workspaces’ is feasible by using H.323 because: video mixing function is not supported by H.323 MCU reception and display of multiple video streams is not supported by H.323 terminals

UoA/CNL TNC 2000 R8 - Projection of the remote workspace’s signals In future, In future, H.323 products should support this requirement by enhancing H.323 MCU and terminal.

UoA/CNL TNC 2000 Display of Multiple workspaces Wi Wx Wy Wz sw Iv/V(Wi) M Speaker MCU M:=Mixed(Iv(Wi),Sv(W*)-Speaker M Speaker Speaker M Speaker:= Sv(Wy) mix M Sv(Wx) Sv(Wi) Sv(Wz)

UoA/CNL TNC 2000 Display of single workspace Wi Wx Wy Wz sw Iv/V(Wi) Sel-V Speaker MCU Sel-V: one of Sv(W*) Sel-V Speaker Speaker Sel-V Speaker:= Sv(Wy) sw Sel-V Sv(Wx) Sv(Wi) Sv(Wz)

UoA/CNL TNC 2000 R9 - Projection of the remote classroom on the instructor’s small size monitor Instructor should attend the remote classrooms in small size monitor(s). Similar requirement to the previous one (R8) - MBONE tools - video H.323 MCU

UoA/CNL TNC 2000 R10 - Lecture broadcasting Broadcasting the lecture to a large number of passive participants H.323 MCU Audio & Video multicasting to passive participants Active participants H.323 MCU Active participants BE MBONE or commercial product

UoA/CNL TNC 2000 R11-Session recording A session should be recorded to be available for latter asynchronous access. Recording is not supported by H.323 Recom. A complementary system should be used, possibly in conjunction with the broadcast system. H.323 MCU Active participants BE + recording MBONE or commercial product

UoA/CNL TNC 2000 R12 - Session management A teleteaching environment should provide a way for: session announcement, scheduling and management. Active participants should be invited. Passive participants should be able to join. Authentication mechanism is optional. Statistics for billing and accounting reasons.

UoA/CNL TNC 2000 Conclusions (1/3) Present H.323 products partly fulfil the teleteaching requirements. H.323 products should be enhanced. H.323 MCU: –stream distribution in multicast (R1,R4,R6) –disable stream transmission of non participating terminals in processing function(s) in (R4,R6) –video mixing, transcoding (R8,R9) –allow video switching of multiple streams (R8,R9) –enable concurrent video mixing and switching (R8,R9).

UoA/CNL TNC 2000 Conclusions (2/3) H.323 terminals: –support multicast communication mode (R1,R4, R6) –be capable of receiving and decoding multiple (at least 2) video streams and displaying them in dual monitor (R8) –support chair control (only for desktop terminals) (R1,R4,R6) Co-operation of H.323 terminals with camera system and microphone system. –Submit and cancel floor requests (R5).

UoA/CNL TNC 2000 Conclusions (3/3) OPEN Question How flexible and cost-effective is the deployment of teleteaching environments based on H.323 products? in comparison to: Scalable and composable architectures for distributed multimedia collaboration such as Mbone tools.

UoA/CNL TNC 2000 Thank you Questions?