I-D Action: draft-ietf-avtcore-multi-party-rtt-mix-13.txt

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Audio/Video Transport Core Maintenance WG of the IETF.

        Title           : RTP-mixer formatting of multi-party Real-time text
        Author          : Gunnar Hellstrom
	Filename        : draft-ietf-avtcore-multi-party-rtt-mix-13.txt
	Pages           : 43
	Date            : 2021-02-10

Abstract:
   Real-time text mixers for multi-party sessions need to identify the
   source of each transmitted group of text so that the text can be
   presented by endpoints in suitable grouping with other text from the
   same source, while new text from other sources is also presented in
   readable grouping as received interleaved in real-time.

   Use of RTT is increasing, and specifically, use in emergency calls is
   increasing.  Emergency call use requires multi-party mixing.  RFC
   4103 "RTP Payload for Text Conversation" mixer implementations can
   use traditional RTP functions for source identification, but the
   performance of the mixer when giving turns for the different sources
   to transmit is limited when using the default transmission
   characteristics with redundancy.

   Enhancements for RFC 4103 real-time text mixing are provided in this
   document, suitable for a centralized conference model that enables
   source identification and rapidly interleaved transmission of text
   from different sources.  The intended use is for real-time text
   mixers and participant endpoints capable of providing an efficient
   presentation or other treatment of a multi-party real-time text
   session.  The specified mechanism builds on the standard use of the
   CSRC list in the RTP packet for source identification.  The method
   makes use of the same "text/t140" and "text/red" formats as for two-
   party sessions.

   Solutions using multiple RTP streams in the same RTP session are
   briefly mentioned, as they could have some benefits over the RTP-
   mixer model.  The possibility to implement the solution in a wide
   range of existing RTP implementations made the RTP-mixer model be
   selected to be fully specified in this document.

   A capability exchange is specified so that it can be verified that a
   mixer and a participant can handle the multi-party coded real-time
   text stream using the RTP-mixer method.  The capability is indicated
   by use of an SDP media attribute "rtt-mixer".

   The document updates RFC 4103 "RTP Payload for Text Conversation".

   A specification of how a mixer can format text for the case when the
   endpoint is not multi-party aware is also provided.


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