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rfc:rfc7205

Internet Engineering Task Force (IETF) A. Romanow Request for Comments: 7205 Cisco Category: Informational S. Botzko ISSN: 2070-1721 M. Duckworth

                                                               Polycom
                                                          R. Even, Ed.
                                                   Huawei Technologies
                                                            April 2014
              Use Cases for Telepresence Multistreams

Abstract

 Telepresence conferencing systems seek to create an environment that
 gives users (or user groups) that are not co-located a feeling of co-
 located presence through multimedia communication that includes at
 least audio and video signals of high fidelity.  A number of
 techniques for handling audio and video streams are used to create
 this experience.  When these techniques are not similar,
 interoperability between different systems is difficult at best, and
 often not possible.  Conveying information about the relationships
 between multiple streams of media would enable senders and receivers
 to make choices to allow telepresence systems to interwork.  This
 memo describes the most typical and important use cases for sending
 multiple streams in a telepresence conference.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7205.

Romanow, et al. Informational [Page 1] RFC 7205 Telepresence Use Cases April 2014

Copyright Notice

 Copyright (c) 2014 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
 2.  Overview of Telepresence Scenarios  . . . . . . . . . . . . .   4
 3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.1.  Point-to-Point Meeting: Symmetric . . . . . . . . . . . .   7
   3.2.  Point-to-Point Meeting: Asymmetric  . . . . . . . . . . .   7
   3.3.  Multipoint Meeting  . . . . . . . . . . . . . . . . . . .   9
   3.4.  Presentation  . . . . . . . . . . . . . . . . . . . . . .  10
   3.5.  Heterogeneous Systems . . . . . . . . . . . . . . . . . .  11
   3.6.  Multipoint Education Usage  . . . . . . . . . . . . . . .  12
   3.7.  Multipoint Multiview (Virtual Space)  . . . . . . . . . .  14
   3.8.  Multiple Presentation Streams - Telemedicine  . . . . . .  15
 4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
 5.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
 6.  Informative References  . . . . . . . . . . . . . . . . . . .  16

Romanow, et al. Informational [Page 2] RFC 7205 Telepresence Use Cases April 2014

1. Introduction

 Telepresence applications try to provide a "being there" experience
 for conversational video conferencing.  Often, this telepresence
 application is described as "immersive telepresence" in order to
 distinguish it from traditional video conferencing and from other
 forms of remote presence not related to conversational video
 conferencing, such as avatars and robots.  The salient
 characteristics of telepresence are often described as: being actual
 sized, providing immersive video, preserving interpersonal
 interaction, and allowing non-verbal communication.
 Although telepresence systems are based on open standards such as RTP
 [RFC3550], SIP [RFC3261], H.264 [ITU.H264], and the H.323 [ITU.H323]
 suite of protocols, they cannot easily interoperate with each other
 without operator assistance and expensive additional equipment that
 translates from one vendor's protocol to another.
 The basic features that give telepresence its distinctive
 characteristics are implemented in disparate ways in different
 systems.  Currently, telepresence systems from diverse vendors
 interoperate to some extent, but this is not supported in a
 standards-based fashion.  Interworking requires that translation and
 transcoding devices be included in the architecture.  Such devices
 increase latency, reducing the quality of interpersonal interaction.
 Use of these devices is often not automatic; it frequently requires
 substantial manual configuration and a detailed understanding of the
 nature of underlying audio and video streams.  This state of affairs
 is not acceptable for the continued growth of telepresence -- these
 systems should have the same ease of interoperability as do
 telephones.  Thus, a standard way of describing the multiple streams
 constituting the media flows and the fundamental aspects of their
 behavior would allow telepresence systems to interwork.
 This document presents a set of use cases describing typical
 scenarios.  Requirements will be derived from these use cases in a
 separate document.  The use cases are described from the viewpoint of
 the users.  They are illustrative of the user experience that needs
 to be supported.  It is possible to implement these use cases in a
 variety of different ways.
 Many different scenarios need to be supported.  This document
 describes in detail the most common and basic use cases.  These will
 cover most of the requirements.  There may be additional scenarios
 that bring new features and requirements that can be used to extend
 the initial work.

Romanow, et al. Informational [Page 3] RFC 7205 Telepresence Use Cases April 2014

 Point-to-point and multipoint telepresence conferences are
 considered.  In some use cases, the number of screens is the same at
 all sites; in others, the number of screens differs at different
 sites.  Both use cases are considered.  Also included is a use case
 describing display of presentation material or content.
 The multipoint use cases may include a variety of systems from
 conference room systems to handheld devices, and such a use case is
 described in the document.
 This document's structure is as follows: Section 2 gives an overview
 of scenarios, and Section 3 describes use cases.

2. Overview of Telepresence Scenarios

 This section describes the general characteristics of the use cases
 and what the scenarios are intended to show.  The typical setting is
 a business conference, which was the initial focus of telepresence.
 Recently, consumer products are also being developed.  We
 specifically do not include in our scenarios the physical
 infrastructure aspects of telepresence, such as room construction,
 layout, and decoration.  Furthermore, these use cases do not describe
 all the aspects needed to create the best user experience (for
 example, the human factors).
 We also specifically do not attempt to precisely define the
 boundaries between telepresence systems and other systems, nor do we
 attempt to identify the "best" solution for each presented scenario.
 Telepresence systems are typically composed of one or more video
 cameras and encoders and one or more display screens of large size
 (diagonal around 60 inches).  Microphones pick up sound, and audio
 codec(s) produce one or more audio streams.  The cameras used to
 capture the telepresence users are referred to as "participant
 cameras" (and likewise for screens).  There may also be other
 cameras, such as for document display.  These will be referred to as
 "presentation cameras" or "content cameras", which generally have
 different formats, aspect ratios, and frame rates from the
 participant cameras.  The presentation streams may be shown on
 participant screens or on auxiliary display screens.  A user's
 computer may also serve as a virtual content camera, generating an
 animation or playing a video for display to the remote participants.
 We describe such a telepresence system as sending one or more video
 streams, audio streams, and presentation streams to the remote
 system(s).

Romanow, et al. Informational [Page 4] RFC 7205 Telepresence Use Cases April 2014

 The fundamental parameters describing today's typical telepresence
 scenarios include:
 1.   The number of participating sites
 2.   The number of visible seats at a site
 3.   The number of cameras
 4.   The number and type of microphones
 5.   The number of audio channels
 6.   The screen size
 7.   The screen capabilities -- such as resolution, frame rate,
      aspect ratio
 8.   The arrangement of the screens in relation to each other
 9.   The number of primary screens at each site
 10.  Type and number of presentation screens
 11.  Multipoint conference display strategies -- for example, the
      camera-to-screen mappings may be static or dynamic
 12.  The camera point of capture
 13.  The cameras fields of view and how they spatially relate to each
      other
 As discussed in the introduction, the basic features that give
 telepresence its distinctive characteristics are implemented in
 disparate ways in different systems.
 There is no agreed upon way to adequately describe the semantics of
 how streams of various media types relate to each other.  Without a
 standard for stream semantics to describe the particular roles and
 activities of each stream in the conference, interoperability is
 cumbersome at best.
 In a multiple-screen conference, the video and audio streams sent
 from remote participants must be understood by receivers so that they
 can be presented in a coherent and life-like manner.  This includes
 the ability to present remote participants at their actual size for
 their apparent distance, while maintaining correct eye contact,

Romanow, et al. Informational [Page 5] RFC 7205 Telepresence Use Cases April 2014

 gesticular cues, and simultaneously providing a spatial audio sound
 stage that is consistent with the displayed video.
 The receiving device that decides how to render incoming information
 needs to understand a number of variables such as the spatial
 position of the speaker, the field of view of the cameras, the camera
 zoom, which media stream is related to each of the screens, etc.  It
 is not simply that individual streams must be adequately described,
 to a large extent this already exists, but rather that the semantics
 of the relationships between the streams must be communicated.  Note
 that all of this is still required even if the basic aspects of the
 streams, such as the bit rate, frame rate, and aspect ratio, are
 known.  Thus, this problem has aspects considerably beyond those
 encountered in interoperation of video conferencing systems that have
 a single camera/screen.

3. Use Cases

 The use cases focus on typical implementations.  There are a number
 of possible variants for these use cases; for example, the audio
 supported may differ at the end points (such as mono or stereo versus
 surround sound), etc.
 Many of these systems offer a "full conference room" solution, where
 local participants sit at one side of a table and remote participants
 are displayed as if they are sitting on the other side of the table.
 The cameras and screens are typically arranged to provide a panoramic
 view of the remote room (left to right from the local user's
 viewpoint).
 The sense of immersion and non-verbal communication is fostered by a
 number of technical features, such as:
 1.  Good eye contact, which is achieved by careful placement of
     participants, cameras, and screens.
 2.  Camera field of view and screen sizes are matched so that the
     images of the remote room appear to be full size.
 3.  The left side of each room is presented on the right screen at
     the far end; similarly, the right side of the room is presented
     on the left screen.  The effect of this is that participants of
     each site appear to be sitting across the table from each other.
     If 2 participants on the same site glance at each other, all
     participants can observe it.  Likewise, if a participant at one
     site gestures to a participant on the other site, all
     participants observe the gesture itself and the participants it
     includes.

Romanow, et al. Informational [Page 6] RFC 7205 Telepresence Use Cases April 2014

3.1. Point-to-Point Meeting: Symmetric

 In this case, each of the 2 sites has an identical number of screens,
 with cameras having fixed fields of view, and 1 camera for each
 screen.  The sound type is the same at each end.  As an example,
 there could be 3 cameras and 3 screens in each room, with stereo
 sound being sent and received at each end.
 Each screen is paired with a corresponding camera.  Each camera/
 screen pair is typically connected to a separate codec, producing an
 encoded stream of video for transmission to the remote site, and
 receiving a similarly encoded stream from the remote site.
 Each system has one or multiple microphones for capturing audio.  In
 some cases, stereophonic microphones are employed.  In other systems,
 a microphone may be placed in front of each participant (or pair of
 participants).  In typical systems, all the microphones are connected
 to a single codec that sends and receives the audio streams as either
 stereo or surround sound.  The number of microphones and the number
 of audio channels are often not the same as the number of cameras.
 Also, the number of microphones is often not the same as the number
 of loudspeakers.
 The audio may be transmitted as multi-channel (stereo/surround sound)
 or as distinct and separate monophonic streams.  Audio levels should
 be matched, so the sound levels at both sites are identical.
 Loudspeaker and microphone placements are chosen so that the sound
 "stage" (orientation of apparent audio sources) is coordinated with
 the video.  That is, if a participant at one site speaks, the
 participants at the remote site perceive her voice as originating
 from her visual image.  In order to accomplish this, the audio needs
 to be mapped at the received site in the same fashion as the video.
 That is, audio received from the right side of the room needs to be
 output from loudspeaker(s) on the left side at the remote site, and
 vice versa.

3.2. Point-to-Point Meeting: Asymmetric

 In this case, each site has a different number of screens and cameras
 than the other site.  The important characteristic of this scenario
 is that the number of screens is different between the 2 sites.  This
 creates challenges that are handled differently by different
 telepresence systems.
 This use case builds on the basic scenario of 3 screens to 3 screens.
 Here, we use the common case of 3 screens and 3 cameras at one site,
 and 1 screen and 1 camera at the other site, connected by a point-to-
 point call.  The screen sizes and camera fields of view at both sites

Romanow, et al. Informational [Page 7] RFC 7205 Telepresence Use Cases April 2014

 are basically similar, such that each camera view is designed to show
 2 people sitting side by side.  Thus, the 1-screen room has up to 2
 people seated at the table, while the 3-screen room may have up to 6
 people at the table.
 The basic considerations of defining left and right and indicating
 relative placement of the multiple audio and video streams are the
 same as in the 3-3 use case.  However, handling the mismatch between
 the 2 sites of the number of screens and cameras requires more
 complicated maneuvers.
 For the video sent from the 1-camera room to the 3-screen room,
 usually what is done is to simply use 1 of the 3 screens and keep the
 second and third screens inactive or, for example, put up the current
 date.  This would maintain the "full-size" image of the remote side.
 For the other direction, the 3-camera room sending video to the
 1-screen room, there are more complicated variations to consider.
 Here are several possible ways in which the video streams can be
 handled.
 1.  The 1-screen system might simply show only 1 of the 3 camera
     images, since the receiving side has only 1 screen.  2 people are
     seen at full size, but 4 people are not seen at all.  The choice
     of which one of the 3 streams to display could be fixed, or could
     be selected by the users.  It could also be made automatically
     based on who is speaking in the 3-screen room, such that the
     people in the 1-screen room always see the person who is
     speaking.  If the automatic selection is done at the sender, the
     transmission of streams that are not displayed could be
     suppressed, which would avoid wasting bandwidth.
 2.  The 1-screen system might be capable of receiving and decoding
     all 3 streams from all 3 cameras.  The 1-screen system could then
     compose the 3 streams into 1 local image for display on the
     single screen.  All 6 people would be seen, but smaller than full
     size.  This could be done in conjunction with reducing the image
     resolution of the streams, such that encode/decode resources and
     bandwidth are not wasted on streams that will be downsized for
     display anyway.
 3.  The 3-screen system might be capable of including all 6 people in
     a single stream to send to the 1-screen system.  For example, it
     could use PTZ (Pan Tilt Zoom) cameras to physically adjust the
     cameras such that 1 camera captures the whole room of 6 people.
     Or, it could recompose the 3 camera images into 1 encoded stream
     to send to the remote site.  These variations also show all 6
     people but at a reduced size.

Romanow, et al. Informational [Page 8] RFC 7205 Telepresence Use Cases April 2014

 4.  Or, there could be a combination of these approaches, such as
     simultaneously showing the speaker in full size with a composite
     of all 6 participants in a smaller size.
 The receiving telepresence system needs to have information about the
 content of the streams it receives to make any of these decisions.
 If the systems are capable of supporting more than one strategy,
 there needs to be some negotiation between the 2 sites to figure out
 which of the possible variations they will use in a specific point-
 to-point call.

3.3. Multipoint Meeting

 In a multipoint telepresence conference, there are more than 2 sites
 participating.  Additional complexity is required to enable media
 streams from each participant to show up on the screens of the other
 participants.
 Clearly, there are a great number of topologies that can be used to
 display the streams from multiple sites participating in a
 conference.
 One major objective for telepresence is to be able to preserve the
 "being there" user experience.  However, in multi-site conferences,
 it is often (in fact, usually) not possible to simultaneously provide
 full-size video, eye contact, and common perception of gestures and
 gaze by all participants.  Several policies can be used for stream
 distribution and display: all provide good results, but they all make
 different compromises.
 One common policy is called site switching.  Let's say the speaker is
 at site A and the other participants are at various "remote" sites.
 When the room at site A shown, all the camera images from site A are
 forwarded to the remote sites.  Therefore, at each receiving remote
 site, all the screens display camera images from site A.  This can be
 used to preserve full-size image display, and also provide full
 visual context of the displayed far end, site A.  In site switching,
 there is a fixed relation between the cameras in each room and the
 screens in remote rooms.  The room or participants being shown are
 switched from time to time based on who is speaking or by manual
 control, e.g., from site A to site B.
 Segment switching is another policy choice.  In segment switching
 (assuming still that site A is where the speaker is, and "remote"
 refers to all the other sites), rather than sending all the images
 from site A, only the speaker at site A is shown.  The camera images
 of the current speaker and previous speakers (if any) are forwarded
 to the other sites in the conference.  Therefore, the screens in each

Romanow, et al. Informational [Page 9] RFC 7205 Telepresence Use Cases April 2014

 site are usually displaying images from different remote sites -- the
 current speaker at site A and the previous ones.  This strategy can
 be used to preserve full-size image display and also capture the non-
 verbal communication between the speakers.  In segment switching, the
 display depends on the activity in the remote rooms (generally, but
 not necessarily based on audio/speech detection).
 A third possibility is to reduce the image size so that multiple
 camera views can be composited onto one or more screens.  This does
 not preserve full-size image display, but it provides the most visual
 context (since more sites or segments can be seen).  Typically in
 this case, the display mapping is static, i.e., each part of each
 room is shown in the same location on the display screens throughout
 the conference.
 Other policies and combinations are also possible.  For example,
 there can be a static display of all screens from all remote rooms,
 with part or all of one screen being used to show the current speaker
 at full size.

3.4. Presentation

 In addition to the video and audio streams showing the participants,
 additional streams are used for presentations.
 In systems available today, generally only one additional video
 stream is available for presentations.  Often, this presentation
 stream is half-duplex in nature, with presenters taking turns.  The
 presentation stream may be captured from a PC screen, or it may come
 from a multimedia source such as a document camera, camcorder, or a
 DVD.  In a multipoint meeting, the presentation streams for the
 currently active presentation are always distributed to all sites in
 the meeting, so that the presentations are viewed by all.
 Some systems display the presentation streams on a screen that is
 mounted either above or below the 3 participant screens.  Other
 systems provide screens on the conference table for observing
 presentations.  If multiple presentation screens are used, they
 generally display identical content.  There is considerable variation
 in the placement, number, and size of presentation screens.
 In some systems, presentation audio is pre-mixed with the room audio.
 In others, a separate presentation audio stream is provided (if the
 presentation includes audio).

Romanow, et al. Informational [Page 10] RFC 7205 Telepresence Use Cases April 2014

 In H.323 [ITU.H323] systems, H.239 [ITU.H239] is typically used to
 control the video presentation stream.  In SIP systems, similar
 control mechanisms can be provided using the Binary Floor Control
 Protocol (BFCP) [RFC4582] for the presentation token.  These
 mechanisms are suitable for managing a single presentation stream.
 Although today's systems remain limited to a single video
 presentation stream, there are obvious uses for multiple presentation
 streams:
 1.  Frequently, the meeting convener is following a meeting agenda,
     and it is useful for her to be able to show that agenda to all
     participants during the meeting.  Other participants at various
     remote sites are able to make presentations during the meeting,
     with the presenters taking turns.  The presentations and the
     agenda are both shown, either on separate screens, or perhaps
     rescaled and shown on a single screen.
 2.  A single multimedia presentation can itself include multiple
     video streams that should be shown together.  For instance, a
     presenter may be discussing the fairness of media coverage.  In
     addition to slides that support the presenter's conclusions, she
     also has video excerpts from various news programs that she shows
     to illustrate her findings.  She uses a DVD player for the video
     excerpts so that she can pause and reposition the video as
     needed.
 3.  An educator who is presenting a multiscreen slide show.  This
     show requires that the placement of the images on the multiple
     screens at each site be consistent.
 There are many other examples where multiple presentation streams are
 useful.

3.5. Heterogeneous Systems

 It is common in meeting scenarios for people to join the conference
 from a variety of environments, using different types of endpoint
 devices.  A multiscreen immersive telepresence conference may include
 someone on a PC-based video conferencing system, a participant
 calling in by phone, and (soon) someone on a handheld device.
 What experience/view will each of these devices have?
 Some may be able to handle multiple streams, and others can handle
 only a single stream.  (Here, we are not talking about legacy
 systems, but rather systems built to participate in such a
 conference, although they are single stream only.)  In a single video

Romanow, et al. Informational [Page 11] RFC 7205 Telepresence Use Cases April 2014

 stream, the stream may contain one or more compositions depending on
 the available screen space on the device.  In most cases, an
 intermediate transcoding device will be relied upon to produce a
 single stream, perhaps with some kind of continuous presence.
 Bit rates will vary -- the handheld device and phone having lower bit
 rates than PC and multiscreen systems.
 Layout is accomplished according to different policies.  For example,
 a handheld device and PC may receive the active speaker stream.  The
 decision can either be made explicitly by the receiver or by the
 sender if it can receive some kind of rendering hint.  The same is
 true for audio -- i.e., that it receives a mixed stream or a number
 of the loudest speakers if mixing is not available in the network.
 For the PC-based conferencing participant, the user's experience
 depends on the application.  It could be single stream, similar to a
 handheld device but with a bigger screen.  Or, it could be multiple
 streams, similar to an immersive telepresence system but with a
 smaller screen.  Control for manipulation of streams can be local in
 the software application, or in another location and sent to the
 application over the network.
 The handheld device is the most extreme.  How will that participant
 be viewed and heard?  It should be an equal participant, though the
 bandwidth will be significantly less than an immersive system.  A
 receiver may choose to display output coming from a handheld device
 differently based on the resolution, but that would be the case with
 any low-resolution video stream, e.g., from a powerful PC on a bad
 network.
 The handheld device will send and receive a single video stream,
 which could be a composite or a subset of the conference.  The
 handheld device could say what it wants or could accept whatever the
 sender (conference server or sending endpoint) thinks is best.  The
 handheld device will have to signal any actions it wants to take the
 same way that an immersive system signals actions.

3.6. Multipoint Education Usage

 The importance of this example is that the multiple video streams are
 not used to create an immersive conferencing experience with
 panoramic views at all the sites.  Instead, the multiple streams are
 dynamically used to enable full participation of remote students in a
 university class.  In some instances, the same video stream is
 displayed on multiple screens in the room; in other instances, an
 available stream is not displayed at all.

Romanow, et al. Informational [Page 12] RFC 7205 Telepresence Use Cases April 2014

 The main site is a university auditorium that is equipped with 3
 cameras.  One camera is focused on the professor at the podium.  A
 second camera is mounted on the wall behind the professor and
 captures the class in its entirety.  The third camera is co-located
 with the second and is designed to capture a close-up view of a
 questioner in the audience.  It automatically zooms in on that
 student using sound localization.
 Although the auditorium is equipped with 3 cameras, it is only
 equipped with 2 screens.  One is a large screen located at the front
 so that the class can see it.  The other is located at the rear so
 the professor can see it.  When someone asks a question, the front
 screen shows the questioner.  Otherwise, it shows the professor
 (ensuring everyone can easily see her).
 The remote sites are typical immersive telepresence rooms, each with
 3 camera/screen pairs.
 All remote sites display the professor on the center screen at full
 size.  A second screen shows the entire classroom view when the
 professor is speaking.  However, when a student asks a question, the
 second screen shows the close-up view of the student at full size.
 Sometimes the student is in the auditorium; sometimes the speaking
 student is at another remote site.  The remote systems never display
 the students that are actually in that room.
 If someone at a remote site asks a question, then the screen in the
 auditorium will show the remote student at full size (as if they were
 present in the auditorium itself).  The screen in the rear also shows
 this questioner, allowing the professor to see and respond to the
 student without needing to turn her back on the main class.
 When no one is asking a question, the screen in the rear briefly
 shows a full-room view of each remote site in turn, allowing the
 professor to monitor the entire class (remote and local students).
 The professor can also use a control on the podium to see a
 particular site -- she can choose either a full-room view or a
 single-camera view.
 Realization of this use case does not require any negotiation between
 the participating sites.  Endpoint devices (and a Multipoint Control
 Unit (MCU), if present) need to know who is speaking and what video
 stream includes the view of that speaker.  The remote systems need
 some knowledge of which stream should be placed in the center.  The
 ability of the professor to see specific sites (or for the system to
 show all the sites in turn) would also require the auditorium system

Romanow, et al. Informational [Page 13] RFC 7205 Telepresence Use Cases April 2014

 to know what sites are available and to be able to request a
 particular view of any site.  Bandwidth is optimized if video that is
 not being shown at a particular site is not distributed to that site.

3.7. Multipoint Multiview (Virtual Space)

 This use case describes a virtual space multipoint meeting with good
 eye contact and spatial layout of participants.  The use case was
 proposed very early in the development of video conferencing systems
 as described in 1983 by Allardyce and Randal [virtualspace].  The use
 case is illustrated in Figure 2-5 of their report.  The virtual space
 expands the point-to-point case by having all multipoint conference
 participants "seated" in a virtual room.  In this case, each
 participant has a fixed "seat" in the virtual room, so each
 participant expects to see a different view having a different
 participant on his left and right side.  Today, the use case is
 implemented in multiple telepresence-type video conferencing systems
 on the market.  The term "virtual space" was used in their report.
 The main difference between the result obtained with modern systems
 and those from 1983 are larger screen sizes.
 Virtual space multipoint as defined here assumes endpoints with
 multiple cameras and screens.  Usually, there is the same number of
 cameras and screens at a given endpoint.  A camera is positioned
 above each screen.  A key aspect of virtual space multipoint is the
 details of how the cameras are aimed.  The cameras are each aimed on
 the same area of view of the participants at the site.  Thus, each
 camera takes a picture of the same set of people but from a different
 angle.  Each endpoint sender in the virtual space multipoint meeting
 therefore offers a choice of video streams to remote receivers, each
 stream representing a different viewpoint.  For example, a camera
 positioned above a screen to a participant's left may take video
 pictures of the participant's left ear; while at the same time, a
 camera positioned above a screen to the participant's right may take
 video pictures of the participant's right ear.
 Since a sending endpoint has a camera associated with each screen, an
 association is made between the receiving stream output on a
 particular screen and the corresponding sending stream from the
 camera associated with that screen.  These associations are repeated
 for each screen/camera pair in a meeting.  The result of this system
 is a horizontal arrangement of video images from remote sites, one
 per screen.  The image from each screen is paired with the camera
 output from the camera above that screen, resulting in excellent eye
 contact.

Romanow, et al. Informational [Page 14] RFC 7205 Telepresence Use Cases April 2014

3.8. Multiple Presentation Streams - Telemedicine

 This use case describes a scenario where multiple presentation
 streams are used.  In this use case, the local site is a surgery room
 connected to one or more remote sites that may have different
 capabilities.  At the local site, 3 main cameras capture the whole
 room (the typical 3-camera telepresence case).  Also, multiple
 presentation inputs are available: a surgery camera that is used to
 provide a zoomed view of the operation, an endoscopic monitor, a
 flouroscope (X-ray imaging), an ultrasound diagnostic device, an
 electrocardiogram (ECG) monitor, etc.  These devices are used to
 provide multiple local video presentation streams to help the surgeon
 monitor the status of the patient and assist in the surgical process.
 The local site may have 3 main screens and one (or more) presentation
 screen(s).  The main screens can be used to display the remote
 experts.  The presentation screen(s) can be used to display multiple
 presentation streams from local and remote sites simultaneously.  The
 3 main cameras capture different parts of the surgery room.  The
 surgeon can decide the number, the size, and the placement of the
 presentations displayed on the local presentation screen(s).  He can
 also indicate which local presentation captures are provided for the
 remote sites.  The local site can send multiple presentation captures
 to remote sites, and it can receive from them multiple presentations
 related to the patient or the procedure.
 One type of remote site is a single- or dual-screen and one-camera
 system used by a consulting expert.  In the general case, the remote
 sites can be part of a multipoint telepresence conference.  The
 presentation screens at the remote sites allow the experts to see the
 details of the operation and related data.  Like the main site, the
 experts can decide the number, the size, and the placement of the
 presentations displayed on the presentation screens.  The
 presentation screens can display presentation streams from the
 surgery room, from other remote sites, or from local presentation
 streams.  Thus, the experts can also start sending presentation
 streams that can carry medical records, pathology data, or their
 references and analysis, etc.
 Another type of remote site is a typical immersive telepresence room
 with 3 camera/screen pairs, allowing more experts to join the
 consultation.  These sites can also be used for education.  The
 teacher, who is not necessarily the surgeon, and the students are in
 different remote sites.  Students can observe and learn the details
 of the whole procedure, while the teacher can explain and answer
 questions during the operation.

Romanow, et al. Informational [Page 15] RFC 7205 Telepresence Use Cases April 2014

 All remote education sites can display the surgery room.  Another
 option is to display the surgery room on the center screen, and the
 rest of the screens can show the teacher and the student who is
 asking a question.  For all the above sites, multiple presentation
 screens can be used to enhance visibility: one screen for the zoomed
 surgery stream and the others for medical image streams, such as MRI
 images, cardiograms, ultrasonic images, and pathology data.

4. Acknowledgements

 The document has benefitted from input from a number of people
 including Alex Eleftheriadis, Marshall Eubanks, Tommy Andre Nyquist,
 Mark Gorzynski, Charles Eckel, Nermeen Ismail, Mary Barnes, Pascal
 Buhler, and Jim Cole.
 Special acknowledgement to Lennard Xiao, who contributed the text for
 the telemedicine use case, and to Claudio Allocchio for his detailed
 review of the document.

5. Security Considerations

 While there are likely to be security considerations for any solution
 for telepresence interoperability, this document has no security
 considerations.

6. Informative References

 [ITU.H239]  ITU-T, "Role management and additional media channels for
             H.300-series terminals", ITU-T Recommendation H.239,
             September 2005.
 [ITU.H264]  ITU-T, "Advanced video coding for generic audiovisual
             services", ITU-T Recommendation H.264, April 2013.
 [ITU.H323]  ITU-T, "Packet-based Multimedia Communications Systems",
             ITU-T Recommendation H.323, December 2009.
 [RFC3261]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
             A., Peterson, J., Sparks, R., Handley, M., and E.
             Schooler, "SIP: Session Initiation Protocol", RFC 3261,
             June 2002.
 [RFC3550]   Schulzrinne, H., Casner, S., Frederick, R., and V.
             Jacobson, "RTP: A Transport Protocol for Real-Time
             Applications", STD 64, RFC 3550, July 2003.
 [RFC4582]   Camarillo, G., Ott, J., and K. Drage, "The Binary Floor
             Control Protocol (BFCP)", RFC 4582, November 2006.

Romanow, et al. Informational [Page 16] RFC 7205 Telepresence Use Cases April 2014

 [virtualspace]
             Allardyce, L. and L. Randall, "Development of
             Teleconferencing Methodologies with Emphasis on Virtual
             Space Video and Interactive Graphics", April 1983,
             <http://www.dtic.mil/docs/citations/ADA127738>.

Authors' Addresses

 Allyn Romanow
 Cisco
 San Jose, CA  95134
 US
 EMail: allyn@cisco.com
 Stephen Botzko
 Polycom
 Andover, MA  01810
 US
 EMail: stephen.botzko@polycom.com
 Mark Duckworth
 Polycom
 Andover, MA  01810
 US
 EMail: mark.duckworth@polycom.com
 Roni Even (editor)
 Huawei Technologies
 Tel Aviv
 Israel
 EMail: roni.even@mail01.huawei.com

Romanow, et al. Informational [Page 17]

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