Subject: [MMUSIC] Apparent Contradiction In Offer-Answer

From: "Tom-PT Taylor" <[email-masked]>
Date: Wed, 7 Aug 2002 16:53:45 -0400

I found these two passages next to each other in section 6.1 of RFC 3264.
If I strain I can make a case that they do not contradict each other, but I
suspect the second was actually meant to replace the first.

   ... The media formats in the "m=" line MUST be listed in order of
   preference, with the first format listed being preferred.  In this case,
   preferred means that the offerer SHOULD use the format with the
   highest preference from the answer.

   Although the answerer MAY list the formats in their desired order of
   preference, it is RECOMMENDED that unless there is a specific reason,
   the answerer list formats in the same relative order they were
   present in the offer.

Tom Taylor
[email-masked]
Ph. +1 613 736 0961 (ESN 396 1490)

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 12 Aug 2002 23:45:52 -0400

Sorry for the delay. I am only now beginning to recover from a massive 
flood of work at my "real" job:

Tom-PT Taylor wrote:
> I found these two passages next to each other in section 6.1 of RFC
> 3264.  If I strain I can make a case that they do not contradict each
> other, but I suspect the second was actually meant to replace the first.
> 
> 

These are not inconsistent.

The first paragraph is saying that the offerer SHOULD use the highest 
preference codec listed by the answerer. How does the answerer decide 
what his preferences are? The next paragraph recommends that, unless it 
has a reason otherwise, it ought to use the same preferences expressed 
by the offerer.

So, if the offerer says it does codecs 1,2,3 and 4, in that order, the 
answerer (based on the second paragraph), would list codecs 2 and 4, in 
that order, in its answer (assuming it doesn't support 1 and 3). Then, 
based on the first paragraph, the offerer SHOULD use codec 1.

Both paragraphs combined make symmetric codecs (encode and decode with 
the same codec) SHOULD strength.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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