In the context of this WG, the term telepresence is used in a general
manner to describe systems that provide high definition, high quality
audio/video enabling a "being-there" experience. One example is an
immersive telepresence system using specially designed and special
purpose rooms with multiple displays permitting life size image
reproduction using multiple cameras, encoders, decoders, microphones
Current telepresence systems are based on open standards such as RTP,
SIP, H.264, the H.323 suite. However, they cannot easily interoperate
with each other without operator assistance and expensive additional
equipment which translates from one vendor to another. A major factor
limiting the interoperability of telepresence systems is the lack of a
standardized way to describe and negotiate the use of the multiple
streams of audio and video comprising the media flows.
The WG will create specifications for SIP-based conferencing systems
to enable communication of information about media streams so that a
sending system, receiving system, or intermediate system can make
reasonable decisions about transmitting, selecting, and rendering
media streams. This enables systems to make choices that optimize user
This working group is chartered to specify the following information
about media streams from one entity to another entity:
* Spatial relationships of cameras, displays, microphones, and
loudspeakers - relative to each other and to likely positions of
* Viewpoint, field of view/capture for
camera/microphone/display/loudspeaker - so that senders and
intermediate devices can understand how best to compose streams for
receivers, and the receiver will know the characteristics of its
* Usage of the stream, for example whether the stream is presentation,
or document camera output
* Aspect ratio of cameras and displays
* Which sources a receiver wants to receive. For example, it might
want the source for the left camera, or might want the source chosen
by VAD (Voice Activity Detection)
Information between sources and sinks about media stream capabilities
will be exchanged.
The working group will define the semantics, syntax, and transport
mechanism for communicating the necessary information. It will
consider whether existing protocols for signaling, messaging and
transport are adequate or need to be extended. Any extensions to IETF
protocols will be done in appropriate WGs, for example extensions to
SDP in MMUSIC.
The scope of the work includes describing relatively static relations
between entities (participants and devices). It also includes handling
more dynamic relationships, such as specifying the audio and video
streams for defined speakers. Specifying the location of the current
speakers relative to display microphones needs to be provided
dynamically as speakers move.
As part of the receiver telling the sender what it wants dynamically,
explicit receiver notification to the sender of the desired video
stream and video pause will be considered.
The scope includes both systems that provide a fully immersive
experience, and systems that interwork with them and therefore need to
understand the same multiple stream semantics.
The focus of this work is on multiple RTP audio and video streams.
Other media types may be considered, however development of
methodologies for them is not within the scope of this work.
Interoperation with SIP and related standards for audio and video is
required. However, backwards compatibility with existing
non-standards compliant telepresence systems is not required.
This working group is not currently chartered to work on issues of
continuous conference control including: far end camera control, floor
control, conference roster. The working group may identify
interoperability obstacles in existing open standards. If so, the WG
will develop requirements to be communicated to other IETF WGs or
Standards Forums, or recharter as appropriate.
Reuse of existing protocols and backwards compatibility with
SIP-compliant audio/video endpoints are important factors for the
working group to consider. The work will closely coordinate with the
appropriate areas (e.g., OPS and SEC), and working groups including
AVT, MMUSIC, MEDIACTRL, XCON, and SIPCORE.