Re: [AVTCORE] I-D Action: draft-ietf-avtcore-multi-party-rtt-mix-08.txt

Gunnar Hellström <> Sun, 30 August 2020 06:20 UTC

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Date: Sun, 30 Aug 2020 08:20:16 +0200
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Subject: Re: [AVTCORE] I-D Action: draft-ietf-avtcore-multi-party-rtt-mix-08.txt
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I would appreciate comments and reviews on this draft. Other 
organizations want to refer to it.

After some variations of the method to carry multi-party real-time text 
in the previous versions, we are now back to a simple RFC 4103 and 
single RTP stream solution with source indicated in CSRC of the RTP 
packets. In fact it is the same as in the expired predecessor 
draft-hellstrom-text-conference-04, just more elaborated, with 
negotiation by an SDP attribute and an explicit fallback method for 
cases when the endpoint does not support true multi-party presentation.

This was the way recommended by the avtcore session in IETF 108.

I hope you also find it to be the right way to go.



Gunnar Hellström

Den 2020-08-12 kl. 20:52, skrev Gunnar Hellström:
> A new version of the "RTP-mixer formatting of multi-party Real-time 
> text" is available.
> This version moves forward with only two methods for multi-party 
> mixing of RTP transported real-time text.
> The major one is RFC 4103 with transmission interval of 100 ms when 
> there is text from more than one source to transmit, and source 
> indicated in the CSRC list.
> The second one is the fallback for the situation that the endpoint 
> does not have multi-party capability.
> Regards
> Gunnar
> Den 2020-08-12 kl. 20:44, skrev
>> 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-08.txt
>>     Pages           : 36
>>     Date            : 2020-08-12
>> 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.
>>     Regional regulatory requirements specify provision of real-time text
>>     in multi-party calls.  RFC 4103 mixer implementations can use
>>     traditional RTP functions for source identification, but the mixer
>>     source switching performance is limited when using the default
>>     transmission characteristics with redundancy.
>>     Enhancements for RFC 4103 real-time text mixing is provided in this
>>     document, suitable for a centralized conference model that enables
>>     source identification and source switching.  The intended use is for
>>     real-time text mixers and multi-party-aware participant endpoints.
>>     The specified mechanism build on the standard use of the CSRC 
>> list in
>>     the RTP packet for source identification.  The method makes use of
>>     the same "text/red" format as for two-party sessions.
>>     A capability exchange is specified so that it can be verified that a
>>     participant can handle the multi-party coded real-time text stream.
>>     The capability is indicated by use of a media attribute 
>> "rtt-mix-rtp-
>>     mixer".
>>     The document updates RFC 4103[RFC4103]
>>     A specifications of how a mixer can format text for the case when 
>> the
>>     endpoint is not multi-party aware is also provided.
>> The IETF datatracker status page for this draft is:
>> There are also htmlized versions available at:
>> A diff from the previous version is available at:
>> Please note that it may take a couple of minutes from the time of 
>> submission
>> until the htmlized version and diff are available at
>> Internet-Drafts are also available by anonymous FTP at:
>> _______________________________________________
>> Audio/Video Transport Core Maintenance