Sumin,
By my reading the examples you give below are fine. However it sounds
like you may need to work around some implementations that don't support it.
Paul
Sumin Seo wrote:
> Hi All,
>
> I have a question regarding on SDP offer and answer.
> One of our engineers interprets rfc 3264 like below.
> "rfc 3264 doesn't say that answer MUST not include more codecs which are not
> in offer.
> rfc 3264 also says that the answerer MAY list the formats in their desired
> order of preference.
> It is RECOMMENDS that the answerer list formats in the same relative order
> they were present in the offer.
> So, Session MUST be established as long as there is one common codec in
> answer regardless of order of preference or existence of codecs not in
> answer. "
>
> Based on his interpretation, following negotiations should work.
> Offer Answer Offer Answer
> ----------> --------------->
> (a, b, c) (a, b ,c)
> <---------- <----------------
> (d, b, c, e, f) (b, c, d, e, f)
> I did some interop tests with several carriers. As long as first codec in
> answer is one of codecs in offer, calls are successfully connected.
>
> *Can answerer add more codecs which were present in offer?*
> *OR *
> *Should answerer select codecs only in offer and list formats in the same
> relative order they were present in the offer?*
>
>
> Thanks in advance.
> -Sumin.
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