Re: [MMUSIC] I-D Action: draft-ietf-mmusic-sdp-g723-g729-01.txt

worley@ariadne.com (Dale R. Worley) Thu, 23 May 2013 02:05 UTC

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Date: Wed, 22 May 2013 22:04:07 -0400 (EDT)
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From: worley@ariadne.com (Dale R. Worley)
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To: "Parthasarathi R" <partha@parthasarathi.co.in>
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Cc: fluffy@cisco.com, mmusic@ietf.org
Subject: Re: [MMUSIC] I-D Action: draft-ietf-mmusic-sdp-g723-g729-01.txt
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> > From: Cullen Jennings (fluffy)
> > 
> > What happens when an endpoint that understands the [annexb] attribute
> > sends [an] offer to an endpoint that does not understand or implement
> > the [annexb] attribute ?

> From: "Parthasarathi R" <partha@parthasarathi.co.in>
> 
> As per Sec 2.1.9 RFC 4856, "annexb=no" has to be sent by Answerer in case
> the answerer does not support G729 AnnexB. The exact RFC snippet is as
> follows:  
> 
>         "annexb: indicates that Annex B, voice activity detection, is
>         used or preferred.  Permissible values are "yes" and "no"
>         (without the quotes); "yes" is implied if this parameter is
>         omitted."
> 
> Please let me know whether you wish to explicitly mention in the draft that
> Answerer *MUST* send "annexb=no".

No, if the offerer sends "annexb=yes" and the answerer *does not
understand it*, that is, does not support this I-D, the answer will
not contain an annexb parameter.  You should make sure the draft
describes how the *offerer* detects this situation and ensures that
the operation of the codec is done as well as possible.

Dale