Re: [AVTCORE] draft-ietf-avtcore-multi-party-rtt-mix-08.txt - please review

Paul Kyzivat <pkyzivat@alum.mit.edu> Sat, 10 October 2020 18:50 UTC

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From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: Re: [AVTCORE] draft-ietf-avtcore-multi-party-rtt-mix-08.txt - please review
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Gunnar,

I haven't commented on this for some time because it seemed to be 
progressing well and those contributing know more about RTP and RTT than 
I do. Now that it seems to be approaching technical completeness (and 
because I was asked) I have reviewed it again. Here are my thoughts:

* Section 1:

s/by shorting the/by shortening the/

* Section 2.1:

Why was "rtt-mix-rtp-mixer" chosen as the name of the attribute? It 
seems cumbersome and redundant. Wouldn't "rtt-mixer" be sufficient?

* Section 2.1.18.3:

There are two instances of "deduct" here that I think should be "deduce".

* Section 2.1.20:

In the first and second paragraphs the reference to "this section" is 
unclear. I presume it means section 2.1 rather than section 2.1.20 or 
section 2.

In the second paragraph:  s/the the/the/

The third paragraph seems inappropriate for this section of the 
document, since this section is intended to apply only in cases where 
"rtt-mix-rtp-mixer" *has* been negotiated.

* Section 2.2:

The document specifies two alternative mechanisms, one in 2.1 and the 
other in 2.2. But the formatting is very weird because section 2.1 is 
long and detailed while section 2.2 is very short and delegates 
everything to section 3.2.

I suggest reorganizing the document to make this cleaner. E.g., move 
most of the content of content of section 2.1 (all the 2.1.x sections) 
to a new top level section. Then replace that with a small high level 
discussion of the alternative and a delegation to the new section for 
the details.

* Section 3.1:

You talk about "When text is received from multiple original sources 
simultaneously". The meaning of "simultaneously" is pretty fuzzy here. 
Do you think this is sufficient for implementors? You may want to say more.

* Section 8.1:

Please just omit "Attribute syntax:  a=rtt-mix-rtp-mixer". It is only 
for attributes that have values.

That's all. Generally looking good.

	Thanks,
	Paul

On 10/9/20 3:36 PM, Gunnar Hellström wrote:
> I would like to get review comments on 
> draft-ietf-avtcore-multi-party-rtt-mix-08.txt.
> 
> There are three small changes pending:
> 
> 1. The reference to the WebRTC transport of T.140 real-time text is 
> about to be changed from 
> draft-ietf-mmusic-t140-usage-data-channel-14.txt to RFC 8865, but even 
> if RFC 8865 is ready, it is awaiting common publication of a cluster of 
> WebRTC related drafts.
> 
> 2. A bit more detail in section 2.1.23 about the recovery situations in 
> case of packet loss.
> 
> 3. Correction of a minor error  in 2.1.23, where "A1" in the text under 
> packet 6 should be "A3".
> 
> Any further comments would be appreciated so that the draft can be 
> progressed.
> 
> /Gunnar
> 
> 
> 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 internet-drafts@ietf.org:
>>> 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:
>>> https://datatracker.ietf.org/doc/draft-ietf-avtcore-multi-party-rtt-mix/
>>>
>>> There are also htmlized versions available at:
>>> https://tools.ietf.org/html/draft-ietf-avtcore-multi-party-rtt-mix-08
>>> https://datatracker.ietf.org/doc/html/draft-ietf-avtcore-multi-party-rtt-mix-08 
>>>
>>>
>>> A diff from the previous version is available at:
>>> https://www.ietf.org/rfcdiff?url2=draft-ietf-avtcore-multi-party-rtt-mix-08 
>>>
>>>
>>>
>>> Please note that it may take a couple of minutes from the time of 
>>> submission
>>> until the htmlized version and diff are available at tools.ietf.org.
>>>
>>> Internet-Drafts are also available by anonymous FTP at:
>>> ftp://ftp.ietf.org/internet-drafts/
>>>
>>>
>>> _______________________________________________
>>> Audio/Video Transport Core Maintenance
>>> avt@ietf.org
>>> https://www.ietf.org/mailman/listinfo/avt
>>