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Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Obsolete informational reference (is this intentional?): RFC 4582 (Obsoleted by RFC 8855) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 CLUE WG A. Romanow 3 Internet-Draft Cisco 4 Intended status: Informational S. Botzko 5 Expires: January 31, 2013 M. Duckworth 6 Polycom 7 R. Even, Ed. 8 Huawei Technologies 9 T. Eubanks 10 Iformata Communications 11 July 30, 2012 13 Use Cases for Telepresence Multi-streams 14 draft-ietf-clue-telepresence-use-cases-03.txt 16 Abstract 18 Telepresence conferencing systems seek to create the sense of really 19 being present for the participants. A number of techniques for 20 handling audio and video streams are used to create this experience. 21 When these techniques are not similar, interoperability between 22 different systems is difficult at best, and often not possible. 23 Conveying information about the relationships between multiple 24 streams of media would allow senders and receivers to make choices to 25 allow telepresence systems to interwork. This memo describes the 26 most typical and important use cases for sending multiple streams in 27 a telepresence conference. 29 Status of this Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on January 31, 2013. 46 Copyright Notice 48 Copyright (c) 2012 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Telepresence Scenarios Overview . . . . . . . . . . . . . . . 3 65 3. Use Case Scenarios . . . . . . . . . . . . . . . . . . . . . . 6 66 3.1. Point to point meeting: symmetric . . . . . . . . . . . . 6 67 3.2. Point to point meeting: asymmetric . . . . . . . . . . . . 7 68 3.3. Multipoint meeting . . . . . . . . . . . . . . . . . . . . 9 69 3.4. Presentation . . . . . . . . . . . . . . . . . . . . . . . 10 70 3.5. Heterogeneous Systems . . . . . . . . . . . . . . . . . . 11 71 3.6. Multipoint Education Usage . . . . . . . . . . . . . . . . 12 72 3.7. Multipoint Multiview (Virtual space) . . . . . . . . . . . 13 73 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 74 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 75 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 76 7. Informative References . . . . . . . . . . . . . . . . . . . . 15 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 79 1. Introduction 81 Telepresence applications try to provide a "being there" experience 82 for conversational video conferencing. Often this telepresence 83 application is described as "immersive telepresence" in order to 84 distinguish it from traditional video conferencing, and from other 85 forms of remote presence not related to conversational video 86 conferencing, such as avatars and robots. The salient 87 characteristics of telepresence are often described as: actual sized, 88 immersive video, preserving interpersonal interaction and allowing 89 non-verbal communication. 91 Although telepresence systems are based on open standards such as RTP 92 [RFC3550], SIP [RFC3261], H.264, and the H.323[ITU.H323]suite of 93 protocols, they cannot easily interoperate with each other without 94 operator assistance and expensive additional equipment which 95 translates from one vendor's protocol to another. A standard way of 96 describing the multiple streams constituting the media flows and the 97 fundamental aspects of their behavior, would allow telepresence 98 systems to interwork. 100 This draft presents a set of use cases describing typical scenarios. 101 Requirements will be derived from these use cases in a separate 102 document. The use cases are described from the viewpoint of the 103 users. They are illustrative of the user experience that needs to be 104 supported. It is possible to implement these use cases in a variety 105 of different ways. 107 Many different scenarios need to be supported. This document 108 describes in detail the most common and basic use cases. These will 109 cover most of the requirements. There may be additional scenarios 110 that bring new features and requirements which can be used to extend 111 the initial work. 113 Point-to-point and Multipoint telepresence conferences are 114 considered. In some use cases, the number of displays is the same at 115 all sites, in others, the number of displays differs at different 116 sites. Both use cases are considered. Also included is a use case 117 describing display of presentation material or content. 119 The document structure is as follows:Section 2 gives an overview of 120 scenarios, and Section 3 describes use cases. 122 2. Telepresence Scenarios Overview 124 This section describes the general characteristics of the use cases 125 and what the scenarios are intended to show. The typical setting is 126 a business conference, which was the initial focus of telepresence. 127 Recently consumer products are also being developed. We specifically 128 do not include in our scenarios the infrastructure aspects of 129 telepresence, such as room construction, layout and decoration. 131 Telepresence systems are typically composed of one or more video 132 cameras and encoders and one or more display monitors of large size 133 (diagonal around 60"). Microphones pick up sound and audio 134 codec(s)produce one or more audio streams. The cameras used to 135 capture the telepresence users we will call participant cameras (and 136 likewise for displays). There may also be other cameras, such as for 137 document display. These will be referred to as presentation or 138 content cameras, which generally have different formats, aspect 139 ratios, and frame rates from the participant cameras. The 140 presentation streams may be shown on participant monitor, or on 141 auxiliary display monitors. A user's computer may also serve as a 142 virtual content camera, generating an animation or playing back a 143 video for display to the remote participants. 145 We describe such a telepresence system as sending M video streams, N 146 audio streams, and D content streams to the remote system(s). (Note 147 that the number of audio streams is generally not the same as the 148 number of video streams.) 150 The fundamental parameters describing today's typical telepresence 151 scenario include: 153 1. The number of participating sites 155 2. The number of visible seats at a site 157 3. The number of cameras 159 4. The number and type of microphones 161 5. The number of audio channels 163 6. The screen size 165 7. The display capabilities - such as resolution, frame rate, 166 aspect ratio 168 8. The arrangement of the monitors in relation to each other 170 9. The same or a different number of primary monitors at all sites 172 10. Type and number of presentation monitors 173 11. Multipoint conference display strategies - for example, the 174 camera-to-display mappings may be static or dynamic 176 12. The camera viewpoint 178 13. The cameras fields of view and how they do or do not overlap 180 The basic features that give telepresence its distinctive 181 characteristics are implemented in disparate ways in different 182 systems. Currently Telepresence systems from diverse vendors 183 interoperate to some extent, but this is not supported in a standards 184 based fashion. Interworking requires that translation and 185 transcoding devices be included in the architecture. Such devices 186 increase latency, reducing the quality of interpersonal interaction. 187 Use of these devices is often not automatic; it frequently requires 188 substantial manual configuration and a detailed understanding of the 189 nature of underlying audio and video streams. This state of affairs 190 is not acceptable for the continued growth of telepresence - 191 telepresence systems should have the same ease of interoperability as 192 do telephones. 194 There is no agreed upon way to adequately describe the semantics of 195 how streams of various media types relate to each other. Without a 196 standard for stream semantics to describe the particular roles and 197 activities of each stream in the conference, interoperability is 198 cumbersome at best. 200 In a multiple screen conference, the video and audio streams sent 201 from remote participants must be understood by receivers so that they 202 can be presented in a coherent and life-like manner. This includes 203 the ability to present remote participants at their actual size for 204 their apparent distance, while maintaining correct eye contact, 205 gesticular cues, and simultaneously providing a spatial audio sound 206 stage that is consistent with the displayed video. 208 The receiving device that decides how to display incoming information 209 needs to understand a number of variables such as the spatial 210 position of the speaker, the field of view of the cameras; the camera 211 zoom; which media stream is related to each of the displays; etc. It 212 is not simply that individual streams must be adequately described, 213 to a large extent this already exists, but rather that the semantics 214 of the relationships between the streams must be communicated. Note 215 that all of this is still required even if the basic aspects of the 216 streams, such as the bit rate, frame rate, and aspect ratio, are 217 known. Thus, this problem has aspects considerably beyond those 218 encountered in interoperation of single-node video conferencing 219 units. 221 3. Use Case Scenarios 223 Our development of use cases is staged, initially focusing on what is 224 currently typical and important. Use cases that add future or more 225 specialized features will be added later as needed. Also, there are 226 a number of possible variants for these use cases, for example, the 227 audio supported may differ at the end points (such as mono or stereo 228 versus surround sound), etc. 230 The use cases here are intended to be hierarchical, in that the 231 earlier use cases describe basics of telepresence that will also be 232 used by later use cases. 234 Many of these systems offer a full conference room solution where 235 local participants sit on one side of a table and remote participants 236 are displayed as if they are sitting on the other side of the table. 237 The cameras and screens are typically arranged to provide a panoramic 238 (left to right from the local user view point) view of the remote 239 room. 241 The sense of immersion and non-verbal communication is fostered by a 242 number of technical features, such as: 244 1. Good eye contact, which is achieved by careful placement of 245 participants, cameras and screens. 247 2. Camera field of view and screen sizes are matched so that the 248 images of the remote room appear to be full size. 250 3. The left side of each room is presented on the right display at 251 the far end; similarly the right side of the room is presented on 252 the left display. The effect of this is that participants of 253 each site appear to be sitting across the table from each other. 254 If two participants on the same site glance at each other, all 255 participants can observe it. Likewise, if a participant on one 256 site gestures to a participant on the other site, all 257 participants observe the gesture itself and the participants it 258 includes. 260 3.1. Point to point meeting: symmetric 262 In this case each of the two sites has an identical number of 263 screens, with cameras having fixed fields of view, and one camera for 264 each screen. The sound type is the same at each end. As an example, 265 there could be 3 cameras and 3 screens in each room, with stereo 266 sound being sent and received at each end. 268 The important thing here is that each of the 2 sites has the same 269 number of screens. Each screen is paired with a corresponding 270 camera. Each camera / screen pair is typically connected to a 271 separate codec, producing a video encoded stream for transmission to 272 the remote site, and receiving a similarly encoded stream from the 273 remote site. 275 Each system has one or multiple microphones for capturing audio. In 276 some cases, stereophonic microphones are employed. In other systems, 277 a microphone may be placed in front of each participant (or pair of 278 participants). In typical systems all the microphones are connected 279 to a single codec that sends and receives the audio streams as either 280 stereo or surround sound. The number of microphones and the number 281 of audio channels are often not the same as the number of cameras. 282 Also the number of microphones is often not the same as the number of 283 loudspeakers. 285 The audio may be transmitted as multi-channel (stereo/surround sound) 286 or as distinct and separate monophonic streams. Audio levels should 287 be matched, so the sound levels at both sites are identical. 288 Loudspeaker and microphone placements are chosen so that the sound 289 "stage" (orientation of apparent audio sources) is coordinated with 290 the video. That is, if a participant on one site speaks, the 291 participants at the remote site perceive her voice as originating 292 from her visual image. In order to accomplish this, the audio needs 293 to be mapped at the received site in the same fashion as the video. 294 That is, audio received from the right side of the room needs to be 295 output from loudspeaker(s) on the left side at the remote site, and 296 vice versa. 298 3.2. Point to point meeting: asymmetric 300 In this case, each site has a different number of screens and cameras 301 than the other site. The important characteristic of this scenario 302 is that the number of displays is different between the two sites. 303 This creates challenges which are handled differently by different 304 telepresence systems. 306 This use case builds on the basic scenario of 3 screens to 3 screens. 307 Here, we use the common case of 3 screens and 3 cameras at one site, 308 and 1 screen and 1 camera at the other site, connected by a point to 309 point call. The display sizes and camera fields of view at both 310 sites are basically similar, such that each camera view is designed 311 to show two people sitting side by side. Thus the 1 screen room has 312 up to 2 people seated at the table, while the 3 screen room may have 313 up to 6 people at the table. 315 The basic considerations of defining left and right and indicating 316 relative placement of the multiple audio and video streams are the 317 same as in the 3-3 use case. However, handling the mismatch between 318 the two sites of the number of displays and cameras requires more 319 complicated manoeuvres. 321 For the video sent from the 1 camera room to the 3 screen room, 322 usually what is done is to simply use 1 of the 3 displays and keep 323 the second and third displays inactive, or put up the date, for 324 example. This would maintain the "full size" image of the remote 325 side. 327 For the other direction, the 3 camera room sending video to the 1 328 screen room, there are more complicated variations to consider. Here 329 are several possible ways in which the video streams can be handled. 331 1. The 1 screen system might simply show only 1 of the 3 camera 332 images, since the receiving side has only 1 screen. Two people 333 are seen at full size, but 4 people are not seen at all. The 334 choice of which 1 of the 3 streams to display could be fixed, or 335 could be selected by the users. It could also be made 336 automatically based on who is speaking in the 3 screen room, such 337 that the people in the 1 screen room always see the person who is 338 speaking. If the automatic selection is done at the sender, the 339 transmission of streams that are not displayed could be 340 suppressed, which would avoid wasting bandwidth. 342 2. The 1 screen system might be capable of receiving and decoding 343 all 3 streams from all 3 cameras. The 1 screen system could then 344 compose the 3 streams into 1 local image for display on the 345 single screen. All six people would be seen, but smaller than 346 full size. This could be done in conjunction with reducing the 347 image resolution of the streams, such that encode/decode 348 resources and bandwidth are not wasted on streams that will be 349 downsized for display anyway. 351 3. The 3 screen system might be capable of including all 6 people in 352 a single stream to send to the 1 screen system. For example, it 353 could use PTZ (Pan Tilt Zoom) cameras to physically adjust the 354 cameras such that 1 camera captures the whole room of six people. 355 Or it could recompose the 3 camera images into 1 encoded stream 356 to send to the remote site. These variations also show all six 357 people, but at a reduced size. 359 4. Or, there could be a combination of these approaches, such as 360 simultaneously showing the speaker in full size with a composite 361 of all the 6 participants in smaller size. 363 The receiving telepresence system needs to have information about the 364 content of the streams it receives to make any of these decisions. 366 If the systems are capable of supporting more than one strategy, 367 there needs to be some negotiation between the two sites to figure 368 out which of the possible variations they will use in a specific 369 point to point call. 371 3.3. Multipoint meeting 373 In a multipoint telepresence conference, there are more than two 374 sites participating. Additional complexity is required to enable 375 media streams from each participant to show up on the displays of the 376 other participants. 378 Clearly, there are a great number of topologies that can be used to 379 display the streams from multiple sites participating in a 380 conference. 382 One major objective for telepresence is to be able to preserve the 383 "Being there" user experience. However, in multi-site conferences it 384 is often (in fact usually) not possible to simultaneously provide 385 full size video, eye contact, common perception of gestures and gaze 386 by all participants. Several policies can be used for stream 387 distribution and display: all provide good results but they all make 388 different compromises. 390 One common policy is called site switching. Let's say the speaker is 391 at site A and everyone else is at a "remote" site. When the room at 392 site A shown, all the camera images from site A are forwarded to the 393 remote sites. Therefore at each receiving remote site, all the 394 screens display camera images from site A. This can be used to 395 preserve full size image display, and also provide full visual 396 context of the displayed far end, site A. In site switching, there is 397 a fixed relation between the cameras in each room and the displays in 398 remote rooms. The room or participants being shown is switched from 399 time to time based on who is speaking or by manual control, e.g., 400 from site A to site B. 402 Segment switching is another policy choice. Still using site A as 403 where the speaker is, and "remote" to refer to all the other sites, 404 in segment switching, rather than sending all the images from site A, 405 only the speaker at site A is shown. The camera images of the 406 current speaker and previous speakers (if any) are forwarded to the 407 other sites in the conference. Therefore the screens in each site 408 are usually displaying images from different remote sites - the 409 current speaker at site A and the previous ones. This strategy can 410 be used to preserve full size image display, and also capture the 411 non-verbal communication between the speakers. In segment switching, 412 the display depends on the activity in the remote rooms - generally, 413 but not necessarily based on audio / speech detection). 415 A third possibility is to reduce the image size so that multiple 416 camera views can be composited onto one or more screens. This does 417 not preserve full size image display, but provides the most visual 418 context (since more sites or segments can be seen). Typically in 419 this case the display mapping is static, i.e., each part of each room 420 is shown in the same location on the display screens throughout the 421 conference. 423 Other policies and combinations are also possible. For example, 424 there can be a static display of all screens from all remote rooms, 425 with part or all of one screen being used to show the current speaker 426 at full size. 428 3.4. Presentation 430 In addition to the video and audio streams showing the participants, 431 additional streams are used for presentations. 433 In systems available today, generally only one additional video 434 stream is available for presentations. Often this presentation 435 stream is half-duplex in nature, with presenters taking turns. The 436 presentation stream may be captured from a PC screen, or it may come 437 from a multimedia source such as a document camera, camcorder or a 438 DVD. In a multipoint meeting, the presentation streams for the 439 currently active presentation are always distributed to all sites in 440 the meeting, so that the presentations are viewed by all. 442 Some systems display the presentation streams on a screen that is 443 mounted either above or below the three participant screens. Other 444 systems provide monitors on the conference table for observing 445 presentations. If multiple presentation monitors are used, they 446 generally display identical content. There is considerable variation 447 in the placement, number, and size or presentation displays. 449 In some systems presentation audio is pre-mixed with the room audio. 450 In others, a separate presentation audio stream is provided (if the 451 presentation includes audio). 453 In H.323[ITU.H323] systems, H.239[ITU.H239] is typically used to 454 control the video presentation stream. In SIP systems, similar 455 control mechanisms can be provided using BFCP [RFC4582] for 456 presentation token. These mechanisms are suitable for managing a 457 single presentation stream. 459 Although today's systems remain limited to a single video 460 presentation stream, there are obvious uses for multiple presentation 461 streams: 463 1. Frequently the meeting convener is following a meeting agenda, 464 and it is useful for her to be able to show that agenda to all 465 participants during the meeting. Other participants at various 466 remote sites are able to make presentations during the meeting, 467 with the presenters taking turns. The presentations and the 468 agenda are both shown, either on separate displays, or perhaps 469 re-scaled and shown on a single display. 471 2. A single multimedia presentation can itself include multiple 472 video streams that should be shown together. For instance, a 473 presenter may be discussing the fairness of media coverage. In 474 addition to slides which support the presenter's conclusions, she 475 also has video excerpts from various news programs which she 476 shows to illustrate her findings. She uses a DVD player for the 477 video excerpts so that she can pause and reposition the video as 478 needed. 480 3. An educator who is presenting a multi-screen slide show. This 481 show requires that the placement of the images on the multiple 482 displays at each site be consistent. 484 There are many other examples where multiple presentation streams are 485 useful. 487 3.5. Heterogeneous Systems 489 It is common in meeting scenarios for people to join the conference 490 from a variety of environments, using different types of endpoint 491 devices. A multi-screen immersive telepresence conference may 492 include someone on a PC-based video conferencing system, a 493 participant calling in by phone, and (soon) someone on a handheld 494 device. 496 What experience/view will each of these devices have? 498 Some may be able to handle multiple streams and others can handle 499 only a single stream. (We are not here talking about legacy systems, 500 but rather systems built to participate in such a conference, 501 although they are single stream only.) In a single video stream , 502 the stream may contain one or more compositions depending on the 503 available screen space on the device. In most cases an intermediate 504 transcoding device will be relied upon to produce a single stream, 505 perhaps with some kind of continuous presence. 507 Bit rates will vary - the handheld and phone having lower bit rates 508 than PC and multi-screen systems. 510 Layout is accomplished according to different policies. For example, 511 a handheld and PC may receive the active speaker stream. The 512 decision can either be made explicitly by the receiver or by the 513 sender if it can receive some kind of rendering hint. The same is 514 true for audio -- i.e., that it receives a mixed stream or a number 515 of the loudest speakers if mixing is not available in the network. 517 For the PC based conferencing participant, the user's experience 518 depends on the application. It could be single stream, similar to a 519 handheld but with a bigger screen. Or, it could be multiple streams, 520 similar to an immersive telepresence system but with a smaller 521 screen. Control for manipulation of streams can be local in the 522 software application, or in another location and sent to the 523 application over the network. 525 The handheld device is the most extreme. How will that participant 526 be viewed and heard? It should be an equal participant, though the 527 bandwidth will be significantly less than an immersive system. A 528 receiver may choose to display output coming from a handheld 529 differently based on the resolution, but that would be the case with 530 any low resolution video stream, e. g., from a powerful PC on a bad 531 network. 533 The handheld will send and receive a single video stream, which could 534 be a composite or a subset of the conference. The handheld could say 535 what it wants or could accept whatever the sender (conference server 536 or sending endpoint) thinks is best. The handheld will have to 537 signal any actions it wants to take the same way that immersive 538 system signals actions. 540 3.6. Multipoint Education Usage 542 The importance of this example is that the multiple video streams are 543 not used to create an immersive conferencing experience with 544 panoramic views at all the site. Instead the multiple streams are 545 dynamically used to enable full participation of remote students in a 546 university class. In some instances the same video stream is 547 displayed on multiple displays in the room, in other instances an 548 available stream is not displayed at all. 550 The main site is a university auditorium which is equipped with three 551 cameras. One camera is focused on the professor at the podium. A 552 second camera is mounted on the wall behind the professor and 553 captures the class in its entirety. The third camera is co-located 554 with the second, and is designed to capture a close up view of a 555 questioner in the audience. It automatically zooms in on that 556 student using sound localization. 558 Although the auditorium is equipped with three cameras, it is only 559 equipped with two screens. One is a large screen located at the 560 front so that the class can see it. The other is located at the rear 561 so the professor can see it. When someone asks a question, the front 562 screen shows the questioner. Otherwise it shows the professor 563 (ensuring everyone can easily see her). 565 The remote sites are typical immersive telepresence room with three 566 camera/screen pairs. 568 All remote sites display the professor on the center screen at full 569 size. A second screen shows the entire classroom view when the 570 professor is speaking. However, when a student asks a question, the 571 second screen shows the close up view of the student at full size. 572 Sometimes the student is in the auditorium; sometimes the speaking 573 student is at another remote site. The remote systems never display 574 the students that are actually in that room. 576 If someone at the remote site asks a question, then the screen in the 577 auditorium will show the remote student at full size (as if they were 578 present in the auditorium itself). The display in the rear also 579 shows this questioner, allowing the professor to see and respond to 580 the student without needing to turn her back on the main class. 582 When no one is asking a question, the screen in the rear briefly 583 shows a full-room view of each remote site in turn, allowing the 584 professor to monitor the entire class (remote and local students). 585 The professor can also use a control on the podium to see a 586 particular site - she can choose either a full-room view or a single 587 camera view. 589 Realization of this use case does not require any negotiation between 590 the participating sites. Endpoint devices (and an MCU if present) - 591 need to know who is speaking and what video stream includes the view 592 of that speaker. The remote systems need some knowledge of which 593 stream should be placed in the center. The ability of the professor 594 to see specific sites (or for the system to show all the sites in 595 turn) would also require the auditorium system to know what sites are 596 available, and to be able to request a particular view of any site. 597 Bandwidth is optimized if video that is not being shown at a 598 particular site is not distributed to that site. 600 3.7. Multipoint Multiview (Virtual space) 602 This use case describes a virtual space multipoint meeting with good 603 eye contact and spatial layout of prticipants.The use case was 604 proposed very early in the development of video conferencing systems 605 as described in 1983 by Allardyce and Randal [virtualspace]. The use 606 case is illustrated in figure 2-5 of their report. The virtual space 607 expands the point to point case by having all multipoint conference 608 participants "seat" in a virtual room. In this case each participant 609 has a fixed "seat" in the virtual room so each participant expects to 610 see a different view having a different participant on his left and 611 right side. Today, the use case is implemented in multiple 612 telepresence type video conferencing systems on the market. The term 613 "virtual space" was used in their report. The main difference 614 between the result obtained with modern systems and those from 1983 615 are larger display sizes. 617 Virtual space multipoint as defined here assumes endpoints with 618 multiple cameras and displays. Usually there is the same number of 619 cameras and displays at a given endpoint. A camera is positioned 620 above each display. A key aspect of virtual space multipoint is the 621 details of how the cameras are aimed. The cameras are each aimed on 622 the same area of view of the participants at the site. Thus each 623 camera takes a picture of the same set of people but from a different 624 angle. Each endpoint sender in the virtual space multipoint meeting 625 therefore offers a choice of video streams to remote receivers, each 626 stream representing a different view point. For example a camera 627 positioned above a display to a participant's left may take video 628 pictures of the participant's left ear while at the same time, a 629 camera positioned above a display to the participant's right may take 630 video pictures of the participant's right ear. 632 Since a sending endpoint has a camera associated with each display, 633 an association is made between the receiving stream output on a 634 particular display and the corresponding sending stream from the 635 camera associated with that display. These associations are repeated 636 for each display/camera pair in a meeting. The result of this system 637 is a horizontal arrangement of video images from remote sites, one 638 per display. The image from each display is paired with the camera 639 output from the camera above that display resulting in excellent eye 640 contact. 642 4. Acknowledgements 644 The draft has benefitted from input from a number of people including 645 Alex Eleftheriadis, Tommy Andre Nyquist, Mark Gorzynski, Charles 646 Eckel, Nermeen Ismail, Mary Barnes, Pascal Buhler, Jim Cole. 648 5. IANA Considerations 650 This document contains no IANA considerations. 652 6. Security Considerations 654 While there are likely to be security considerations for any solution 655 for telepresence interoperability, this document has no security 656 considerations. 658 7. Informative References 660 [ITU.H239] 661 "Role management and additional media channels for H.300- 662 series terminals", ITU-T Recommendation H.239, 663 September 2005. 665 [ITU.H323] 666 "Packet-based Multimedia Communications Systems", ITU- 667 T Recommendation H.323, December 2009. 669 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 670 A., Peterson, J., Sparks, R., Handley, M., and E. 671 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 672 June 2002. 674 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 675 Jacobson, "RTP: A Transport Protocol for Real-Time 676 Applications", STD 64, RFC 3550, July 2003. 678 [RFC4582] Camarillo, G., Ott, J., and K. Drage, "The Binary Floor 679 Control Protocol (BFCP)", RFC 4582, November 2006. 681 [virtualspace] 682 Allardyce and Randall, "Development of Teleconferencing 683 Methodologies With Emphasis on Virtual Space Videe and 684 Interactive Graphics", 1983. 686 Authors' Addresses 688 Allyn Romanow 689 Cisco 690 San Jose, CA 95134 691 US 693 Email: allyn@cisco.com 694 Stephen Botzko 695 Polycom 696 Andover, MA 01810 697 US 699 Email: stephen.botzko@polycom.com 701 Mark Duckworth 702 Polycom 703 Andover, MA 01810 704 US 706 Email: mark.duckworth@polycom.com 708 Roni Even (editor) 709 Huawei Technologies 710 Tel Aviv, 711 Israel 713 Email: even.roni@huawei.com 715 Marshall Eubanks 716 Iformata Communications 717 Dayton, Ohio 45402 718 US 720 Email: marshall.eubanks@ilformata.com