WG Action: RECHARTER: Audio/Video Transport WG (avt)

[IESG Secretary <[e-mail]>]

The charter of the Audio/Video Transport (avt) working group in the
Real-time Applications and Infrastructure Area of the IETF has been
updated. For additional information, please contact the Area Directors 
or the working group Chairs.

+++

Audio/Video Transport (avt)
=============================

Current Status: Active Working Group

Chair(s):
Colin Perkins <[e-mail]> 
Roni Even <[e-mail]> 
Tom Taylor <[e-mail]> 

Real-time Applications and Infrastructure Area Director(s):
Jon Peterson <[e-mail]> 
Cullen Jennings <[e-mail]> 

Real-time Applications and Infrastructure Area Advisor:
Cullen Jennings <[e-mail]> 

Mailing Lists:
General Discussion: [e-mail]
To Subscribe: https://www1.ietf.org/mailman//listinfo/avt
Archive: http://www.ietf.org/mail-archive/web/avt/index.html

Description of Working Group:

The Audio/Video Transport Working Group was formed to specify a 
protocol for real-time transmission of audio and video over unicast 
and multicast UDP/IP. This is the Real-time Transport Protocol, RTP, 
together with its associated profiles and payload formats. The 
current aims of the working group are:

- to review and revise existing payload formats to advance those 
which
are useful to Draft Standard, and to declare others as Historic.
Milestones will be established as a champion for each payload
format is identified.

- to develop payload formats for new media codecs, and to document
best-current practices in payload format design. The group 
continues
to be precluded from work on codecs themselves because of 
overlap with
the other standards bodies, and because the IETF does not have the
ability to effectively review new codecs. An exception was made 
for
the freeware iLBC codec on a highly experimental basis, but 
acceptance
of new codec work is unexpected and subject to rechartering.

- to complete the forward error correction work to update RFC 
2733 in
the form of the ULP payload format

- to extend RTP to work with Source-Specific Multicast sessions with
unicast feedback

- to provide a framing mechanism for RTP over TCP and TLS

- in collaboration with the MPLS and ROHC WGs, to develop a solution
for header compression of RTP across MPLS networks that avoid
decompression and compression at each MPLS node.

- to develop a new RTP profile for the combination of the SRTP 
profile
and the Extended RTP Profile for RTCP-based Feedback (RTP/SAVPF)

- to maintain and enhance the SRTP Profile, with review and input 
from
the Security Area

- to develop a new RTP profile for usage of TFRC (RFC 3448) with RTP
over UDP to allow application developers to gain experience 
with TCP
friendly congestion control.

- to develop a MIB for RTCP XR (RFC 3611).

- to update the RTP MIB, including aligning it with RFC 3550.

- to clarify how RTP is used for media in conferencing with 
centralised
nodes performing relay, translation or mixing of media.

- to develop the mechanisms needed for efficient control of media 
and
its encoding process in RTP based conferencing, both over 
multicast
and transport containing relays, translators and mixers. An 
example of
such a mechanism is a method to request a full intra coded 
frame of
video. This would be used to allow joining participants to receive
video immediately after joining instead of waiting for the next 
intra
coded frame. It also allows mixers to perform switching between 
media
sources without the need to re-encode the media.

- to develop a solution for carrying media meta data, specifically
SMPTE timestamps, to enhance the media stream. Such transport 
may be
done in either RTP or RTCP depending on which is most suitable. 
The WG
may consider if a generalized mechanism should be developed to 
enable
future types of meta data to be easier to include.

- to develop two new metric blocks for the RTCP XR (RFC 3611) 
framework
to provide information on the media quality experienced by the
receiver of RTP flows. One metrics block is for high resolution
measurements of audio and speech quality. A second one for 
providing
information on the quality of video. The timescale to complete 
this
second block and the included metrics are highly dependable on the
development of standardized subjective metrics for video 
quality. The
WG will consider what metrics that are available and if they 
should be
included or not. The metrics blocks shall not duplicate signalling
information anyway necessary for the establishment of the session.

- to specify how the RFC 3550 requirement on RTCP senders to always
send compound packets can be relaxed to allow for non-compound
packets. The specification need to define under which criteria
non-compound RTCP packets may be sent while maintaining the
functionality that motivated the usage of compound RTCP packets
and keep the bandwidth within specified limits.

The longer term goals of the working group are to advance the SRTP 
Profile, the Extended RTP Profile for RTCP-based Feedback, the 
Compressed RTP framework, and the RTP MIB to Draft Standard.

The group has no plans to develop new RTP profiles beyond those 
listed above, but will consider rechartering to produce profile level 
extensions if appropriate.

Milestones:

- Sep 2008 Submit Non-Compound usage specification for PS

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