CCITT SGXV Document #469 Working Party XV/1 February 1989 Specialists Group on Coding for Visual Telephony

SOURCE: JAPAN TITLE : SGXV CONTRIBUTION ON VISUAL TELEPHONE COMMUNICATION PROCESURE The following contributio s beenha n submitte r discussiodfo f 'systeno m aspects f visuao ' l telephon e cominth n i yg Study Grou meetinV pX g (March 13- 22).

International Telegrap d Telephonhan e CO- MXV Consultative Committee March 1989 (CCITT) Original: English

Period 1989-1992 Question: 3, 4/XV

STUDY GROUP XV - CONTRIBUTION

SOURCE: JAPAN TITLE : VISUAL TELEPHONE COMMUNICATION PROCEDURE

1. Introduction This contribution describes a framework for the communication procedure to be included in AV312 "Videoconference systems/terminals" and AV320 "Videophone systems/terminals". Since there are no clear definitions to distinguish between videoconferencing and videophone, "visual telephone" is use o represendt e Questioe titltth th botf eo n f thei ho n s m a 3/XV . Here are discussed visual telephone systems connected through the basic Interfac e primarth r o e y rate interfac e narrowbanth n i e d ISDN.

2. Communication phases and applied Recommendations Communication phases for audiovisual services are divided as follows in Draft AV240 "Principle r communicatiofo s n between audiovisual terminals" f Anneo o Q.4/XV)2 t (se5. x3 § e .

Phase A: Call establishment Phase B: Pre-message transmission Phas Audiovisua: eC l message transmission Phase D: Post-message procedure Phas Cal: eE l release e stipulatear E Phase d an Recn di A s . 1.450 series, while Phase definear eC d in AV250 serie r audiosfo , AV260 serie r videofo s , etc.

- 1 - Doc. #469 Phas s sub-dividei eB d into Phase Bl whice audiovisua th s commoi h l al o nt l terminals and Phase B2 which is specific to detailed parts of visual telephone. The former is defined in AV240 series, while the latter is defined in AV300 series. This contribution discusse e Phasth s. eB2

3. Communicatio ne visua modeth r lfo s telephone Visual telephone systems are characterized by the communication speed if the e configureyar d using switched circuit networks. Since th e communication speeds provided by the narrowband ISDN are at primary rates or lower, one of the communication modes in Table 1 is determined through Phas l procedureeB .

4. r visuaPhasfo 2 eB l telephone 4.1 Items to be negotiated Phase B2 gives a procedure which determines detailed operational parameters, usage/non-usage of optional functions, etc. once a video telephone communication mod s chosei e n through Phas . FollowineBl e gth same principle for Phase Bl (see Draft AV242 in Annex 5 to Q.4/XV), capabilities are first indicated by the receiving side and then the sending side decides common maximum operational parameter controld an s e th s receiving side. The following items r example fo e ,decide b y ma ,d through Phas. eB2 1) Picture format: GIF/Quarter GIF 2) Minimum coded picture interval 1/29.9x 4 t : c whero t 7se l t= e 3) TYPE4 (8x8 block type) attribute: usage/non-usage 4) Video encryption: usage/non-usage 5) Audio encryption: usage/non-usage 6) Forward error correction: usage/non-usage 7) Video scramblin o copgt e with one's density: usage/non-usage 8) Demand refresh: usage/non-usage 9) Equipment connecte e dat theid th aan o dt porr d typesan t : Facsimile, telewriter, still picture transmission equipment, etc. 4.2 Transmission channels Phas l negotiationeB e carriear s t codesusinS dou gBA . BAS, howevern ca , not deal with Phase B2 negotiations due to its capacity limitation since ther e varietear negotiatee f itemyb o o t s d accordin specifio gt c services. ISDN D-channels may be used for the Phase B2 negotiation purpose, but for the time being, in-channel signalling would help easier service expansion. Consequently, use of the data port is proposed for the Phase B2 negotiation. Accordin H.221o gt data , a por t 640a t 0 bit/s r examplefo , s i , sendiny b p u gBAa t se S code;

"011(Data Command) + 00100(6400 bit/s in AC assigned to data" Whe e negotiatioth n s overni e datth , a por s closei t sendiny db BAga S code: "OlKData Command) + 0000(No data; data switched off"

- 2 - Doc. f469 4.3 Protocol A protoco r Phasfo l negotiatio2 eB n shoul e definedn considedb ca e W e .th r following candidates whic e describear h Appendin di o Rect 1 x . H.221; - Simple bit protocol indicating one bit flag for each item to be negotiated - Message channel protocol: such as the one suggested in Rec. H.140

If any data communication protocol is appropriate for the current purpose, it can be another candidate. In case of a simple bit protocol, protection against transmission errors are required. Majority decision e samlogith er co erro r correction cod s usea e d e appliedb n ca .S BA r fo

5. C&I signals required during communication Table 2 lists up control and indication signals which are required during visual telephone communication with their attribute transmissiod san n channels. If any C&I should be synchronized with the video signal, only way to transmit it is to embed it in the coded video signal, eg in the picture header. Remaining C&I signals are transmitted through Application Channel (AC). By f Dato e a us Comman e openeb n d ca BASd C onlA , y when necessar d closeyan d when C&I transmission is finished. Since a data port set up by the Data Command BAS is used both for C&I transmission and data transmission for such visual aid s telewritera s protocoa , l shoul definee db distinguiso t d h between these two purposes. If the number of visual telephone C&I signals is limited, there may be a possibility to use BAS for their transmission (as indicated in COM XV-183, January 1988).

6. Conclusion Visual telephone communication procedur s beeeha n discusse respecn di f o t items to be negotiated in Phase B2, C&I signals required during communication, and transmission channels for these purposes. The contents are summarized as follows; 1) Detailed communication procedures specific to visual telephone are stipulate s Phasda procedure2 eB AV312/320n i s . 2) The e defineyar s Applicatioa d n Channel protocol receivine Th . g side indicates capabilities and the sending side decides the operational parameters. signalI 3C& ) s during communicatio e transmittenar d throug. hAC protoco4A ) s requirei l o shardt e dateth a port between C&visuad an I l aids.

END

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'At Table 1 Communications modes of visual telephone

Visual Channel Coding Syncf o , ISDn I N terface Telephone Rate ISDN Multiple Prima. Mode (kbit/s) Channel Audio Video Data/AC Channels Basic Rate

a 64 B AV254 not req.

b 128 2B/64+64 2 G.72 not req.

c 128 2B/ 128 AV254/3? required

d 384 HO not req. AV312 e 768 2HO AV261* AV320 required applic able f 1152 3HO required not appl ic g 1536 4HO G. 722 required able

h 1536 Hll not req.

i 1920 5HO required

j 1920 H12 t reqno .

* AV26KH. 261 assumes )i o covet d r px64. kbit/30 o t s1 whers i p e

- 4 - Doc. #469 Tabl 2 eC& I signal r visuafo s l telephone

Sync, with Transmis. I signaC& l Source Sink Picture Channel

Freeze Picture coder decoder noC A r o S BA Request Control or MCU

Fast Update Request decoder coder no BAS or AC Control U MC r o

Freeze Picture coder decoder yes embedded in Release Control coded video

U RelateMC d Message terminal terminal no AC or MCU or MCU

Video Loop Request terminal terminal noC A r o S BA Control *

Digital Loop Request terminal terminal no C A BAr o S Contro* l

Spl it-screen sending receiving yes embedden i d Indication terminal terminal coded video

Document Camera sending receiving yes embedded in Indication terminal terminal coded video

AIA Indication ** sending receiving no AC (audio active) terminal terminal

VIA indication ** sending receiving no AC (video active) terminal terminal

VRA indication ** sending receiving no AC (read o activatt y e terminal terminal video)

* See Annex 4 to COM XV-R16 (Nov. 1986). ** See Draft AV320 in Annex 2 to Q.3/XV.

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