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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