Question 3/XV - Visual telephone systems including videoconferencing and videophone (Continuation of Question 4/XV 1985-88) Considering (1) that Recommendation H.100 provides a generic definition of services involving the transmission of visual information and associated speech (monophonic/stereophonic) on networks used for telephony and other telecommunications applications; (2) that such services include videoconferencing and videophone as defined in H.200/AV100-Series Recommendations (see Annexes 1 and 2); (3) that a number of videoconferencing systems are already in operation and interworking of these is required; (4) that a number of administrations are examining the introduction of a videophone service through ISDN and that experiments and trials of such services are in progress in a number of countries; (5) that the scale of the demand has not yet been established; (6) that differing facilities may be required by different classes of subscriber but these have not yet been clearly identified and defined; (7) that the problems of international working will be easier to resolve if they are studied while national plans are still in a preliminary and formative stage; (8) that since digital transmission is economical and suitable for long- distance visual communications it will, therefore, be used for long- distance transmission in the visual telephone service; moreover, narrow- band ISDN and future broadband ISDN will also be used for providing the visual telephone service; (9) that N times 64 kbit/s bit rates are requested for videoconferencing and videophone services, and that such services could be provided on a switched mode basis if synchronization from end to end is available; (10) that in addition to videoconferencing and videophone it is expected that other various services (e.g. video lecturing, video transmission, surveillance and video information retrieval) will be required and that intercommunication between audiovisual terminals for those services is essential; (11) that, for videoconferencing, a reservation system for booking calls is required to ensure connection at the time of actual usage; (12) that both moving and still picture systems are necessary, 1. for the moving picture system: 1.1 What system architecture should be recommended, particularly respecting the use of different modes applying one or two B channels of the ISDN-basic access? 1.2 What system parameters and transmission standards should be recommended? 1.3 What should be recommended for equipment characteristics? 1.4 What characteristics should be recommended for the subscriber terminals and their environments? 1.5 What should be recommended for multipoint visual telephony? 1.6 What Recommendations should be made concerning picture quality and assessment, particularly respecting the use of different modes applying one or two B channels of the ISDN-basic access? 1.7 What Recommendations should be made specifically for videoconferencing? 1.8 What revision of the existing H.100-Series Recommendations is necessary? 2. What system parameters should be recommended for the transmission of still pictures or sequences of still pictures? Points for study 1.System architecture for moving picture system: 1.1Structure of system using ISDN or other networks for different services. 1.2Hypothetical reference connections and circuits. 1.3National extensions. 1.4User interfaces with network. 1.5Synchronization and timing aspects. 1.6Requirements for signalling and switching. 1.7Definitions of setup and disconnect procedures for N x 64 kbit/s channels. 2.System parameters and transmission standards for the moving picture system: 2.1Performance objectives for the HRCs. 2.2Bit rates to be used on the connection. 2.3 Frame structure for different bit rates. 2.4Communication procedures and channels for system control signals. 2.5Characteristics of interface with the local network and with subscriber terminals. 2.6Methods for the separate and combined transmission of sound and picture. 2.7Characteristics of audio channels. 3.Specifications for equipment in the moving picture system: 3.1Specification of world-wide video coding algorithm(s), parameters and equipment in various bit rates such as n x 384 kbit/s and m x 64 kbit/s for narrowband ISDN. 3.2Video coding algorithm, parameters and equipment for Asynchronous Transfer Mode (ATM) in broadband ISDN, in particular: 3.2.1use of static bandwidth flexibility offered by ATM, 3.2.2variable bit rate video coding techniques, 3.2.3influence of cell loss on image quality, 3.2.4coder/decoder synchronization in presence of cell delay jitter, 3.2.5harmonization of distributive and communicative video services. 3.3Transmission equipment especially designed for visual telephony such as remultiplexers, television standards convertors, transcoders, etc. 4.Characteristics for subscriber terminals and their environments in the moving picture system: 4.1Terminal functions desired for various services. 4.2Requirements for the lighting and acoustic environment where terminal equipments are placed. 4.3Interfaces between users and terminals, e.g. for video, speech (monophonic/stereophonic) data, etc. 4.4Functional specifications for interworking - particularly Control and Indication (C&I) signals. 5.Specification of multipoint videoconferencing and videophone systems using standardized video codecs, particularly for: 5.1System architecture. 5.2Communication control protocol. 5.3 Picture processing method. 5.4Speech processing method, taking into account speech quality impairments due to embedded echo suppression schemes in coders. 5.5Data signal handling. 6.Quality aspects for the moving picture system: 6.1Methods of subjective testing including the development of test tapes containing standardized sequences of moving pictures with different degrees of motion. 6.2Evaluation of pictures containing distortion in both spatial and temporal domains. 6.3Effects of large signal delay. 6.4Quality aspects of the tandem connection of codecs. 6.5Quality of Service for the applications concerned. 7. Videoconferencing specifications for the moving picture system: 7.1Specifications of control and data signals for the split screen system and their transmission method. 7.2Specification of communication reservation system - particularly on: 7.2.1necessary information, 7.2.2parameter definition and values, 7.2.3service capabilities, 7.2.4protocol for international working. Notes 1.The study of this Question should be coordinated with: 1.1 Study Group I for services definition, 1.2 Study Group II for network operation issues, 1.3 Study Group XVIII for ISDN issues. 2.A moving picture system always includes associated speech. 3. The study of this Question should be coordinated with the study of Question 21/XV. ANNEX 1 (to Question 3/XV) Outline draft Recommendation H.200/AV.262 codec for audiovisual services at m x 64 kbit/s 1. Scope 2. Brief specification 3. Source coder 3.1 Source format a) Full CIF: 288 lines x 360 pels x 29.97 Hz1 b) Format smaller than full CIF: 1/4 CIF, 144 lines x 180 pels x 29.97 Hz* Note - The possibility of a third format of 4/9(2/3x2/3) CIF is under study. Interconnection between different formats is on the basis of format b). 3.2 Video source coding algorithm 3.3 Data rate control 3.4 Forced updating 4. Video multiplex coder 4.1 Data structure 4.2 Video multiplex arrangement 4.3 Multipoint considerations 5. Video data buffering 6. Transmission coder 6.1 Bit rate 6.2 Video clock justification 6.3 Frame structure as per Recommendation H.221. 6.4 Audio coding 6.5 Data transmission 6.6 Error handling 6.7 Encryption 6.8 Network interface ANNEX 2 (to Question 3/XV) Outline draft Recommendation H.200/AV.320: Videophone systems and terminal equipment Proposed contents 1. Scope 2. Definitions 3. System description Block diagram and identification of elements Signals Use of infrastructure, options of bit rate etc. Call control arrangements Optional enhancements 4. Terminal requirements Audio Video C&I Optional enhancements (including additional C&I) 5. Intercommunications Appendix 1: Study and discussion points 1. Scope This Recommendation covers the technical requirements for videophone services. As a minimum, two videophone services are standardized: narrow-band videophone, and broadband videophone; the possibility of standardizing more than one narrow-band videophone service is not precluded for the time being. (See Appendix 1, Note 1.) The service requirements for videophone services are presented in Recommendation Y.120; video and audio coding systems, and other technical set aspects common to audiovisual services are covered in other Recommendations in the H.200-Series. 2. Definitions (To be completed.) 3. System description 3.1 Block diagram and identification elements Videophone instrument; camera; monitor; microphone; loudspeaker; handset; control unit; audio codec; video codec; transmission multiplex; network termination; interfaces (...); optional enchancements (low speed data port, document camera, facsimile ...); broadband/narrow-band gateway. (NB: for interworking arrangements, see section 5.) 3.2 Signals Videophone signals are classified as video, audio, data 1, and data 2, as follows: -Audio signals are continuous traffic and require real-time transmission (Note 2). -Video signals are also continuous traffic; the bit rate allocated to video signals should be as high as possible, in order to maximize the quality within the available capacity. -Data 1 signals include still pictures, facsimile, and documents, or other facilities requiring bit rates comparable with those for audio or video; this signal occurs only occasionally as required, and may temporarily displace all or part of the audiovisual signal content; it should be noted that data 1 signals are associated only with optional enhancements to the basic videophone system; therefore the opening of a path to carry such signals is preceded by negotiation between the terminals. -Data 2 signals include telewriting/marker, and some system control signals by definition, the path provided for these signals is permanent and at a fairly low bit rate (for example 2400 bits per second). 3.3 Infrastructure and bit rate options The following types of channel configurations for videophone service are being considered: Type A ("Vp 54"): one B-channel (e.g. 16 kbit/s audio and about 46.4 kbit/s video). Type B ("Vp 128" (Note)): two B-channels (e.g. 64 kbit/s audio-plus, 64 kbit/s video), or (e.g. 16 kbit/s audio plus about 109.6 kbit/s video). Type BB ("Vp-BB"): a broadband system (high quality audio and high bit rate video). (Separate Recommendations AV.321, AV.322 ... will be formed for those systems finally selected for standardization.) Note - It is desired to standardize only one configuration for type B from the engineering point of view. This matter is, however, subject to market/service requirements. There must be provision for basic interworking of audiovisual facilities between all such systems standardized, albeit at the qualities applicable to the lower bit rate (Note 3). 3.4 Videophone Vp 64 Use of AV.221 frame structure; use of video coding system H.12y (proposed assignment for video coding Recommendation at 45-128 kbit/s); use of audio coding to possible draft Recommendation (16 kbit/s); identified subset of C&I from Recommendation AV.230 (audiovisual system control and indications). 3.5 Videophone Vp 128 Here are two examples listed. Choice of one of these or other configurations is for further study. 1) Example of 16 kbit/s audio Synchronization of two B-channels (use of H.221 frame structure in both channels); audio coding to possible draft Recommendation; video coding to H.12y (proposed assignment for video coding at 45-110 kbit/s); C&I to Recommendation AV.230. 2) Example of 64 kbit/s audio-plus Use of frame structure AV.221; audio coding to Recommendation G.722 (48- 64 kbit/s ADPCM 7 kHz); video coding to H.12y; C&I to Recommendation AV.230. 3.6 Broadband videophone Frame structure; audio coding to Recommendation G.722; video coding to H.12(m) - (refers to high bit-rate video coding for local networks); C&I Recommendation AV.230. 3.7 Call control arrangements Establishment of audio call prior to establishment of second channel if applicable. 3.8 Optional enhancements (To be completed.) 4. Terminal requirements 4.1 Audio Microphones and sound system; loudspeakers; echo; audio alignment. 4.2 Video Cameras; monitors; lighting; video alignment. 4.3 Control and indications (C&I) C&I are chosen from the general audiovisual set contained in Recommendation AV.230. Very few C&Is are needed for the basic viodeophone service. AIA - indicate audio active: not-AIA shows that the source has been muted; AIA does not indicate whether anyone is actually speaking. VIA - indicates video active: not-VIA is important, indicating that the video source has deliberately been suppressed - there is no transmission fault involved. VRA - ready to activate video; required if mutual readiness of terminals to transmit/receive video is necessary prior to setting up a suitable signal path or activating the exhange on an existing path. 4.4 Optional enhancements Equipment requirements (to be completed). Control and indications: appropriate C&I to be selected from Y.230. 5. Interworking The mechanisms for interworking with other services are described in this section. References made to general mechanisms as set out in Recommendations AV.240, AV.241 ... . 5.1 Interworking between different videophone terminal types Videophones Vp 64 and Vp 128 Videophones Vp 64 and Vp-BB Videophones Vp 128 and Vp-BB 5.2 Interworking with telephony Interworking with ISDN telephones Interworking with PSTN telephones 5.3 Interworking with videoconferencing Videophones Vp 64/Vp 128 and videoconference VC 384 Videophone Vp-BB and videoconference VC 384 Videophones Vp 64/Vp 128 and videoconference VC-BB Videophone Vp-BB and videoconference VC-BB 5.4 Interworking with audiographic teleconferencing 5.5 Interworking with video surveillance Appendix 1 Note 1 - It is anticipated that this Recommendation will be split into a number of Recommendations AV.321, 322 ... each of which would cover a single videophone service (narrow-band, broadband ...). However large parts of these Recommendations would have identical wording, while in the points of divergence the actual choices between alternatives have not yet been made; for the time being therefore it is convenient to treat all the text in a single document. Note 2 - In order to reduce the average bit rate of audio signals, voice activation can be introduced (in which case the audio signals are no longer continuous). Note 3 - Such provision must be in the network, if it is not possible in the terminals.