Subject: [rtcweb] jsep-04 questions about phrasing

From: Michael Procter <[email-masked]>
Date: Thu, 19 Sep 2013 16:40:17 +0100

Hi,

Section 5.2.2 Subsequent Offers

This section starts with the sentence "When createOffer is called a
second (or later) time,".  As far as I can tell, the rest of this
section applies both to subsequent offers created by the original
offerer and also offers created by the original answerer.  In this
second case, createOffer has never been called.  I would suggest
something like "When createOffer is called after the initial
offer/answer exchange,".

Section 5.2.2 11th bullet:

   o  The m= line and corresponding "a=rtpmap" and "a=fmtp" lines MUST
      only include codecs present in the remote description.

Is this necessary?  Can't we offer new codecs in a subsequent offer?
RFC3264 Sec 8.3.2 permits new codecs to be offered, old ones to be
removed etc, with the only constraint being to not reuse dynamic
payload types.

Finally, the two example SDPs both contain "s=-" whereas section 5.2.1
encourages "s= " instead. Personally, I prefer the hyphen, but
consistency is probably more important.

Regards,

Michael

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From: Justin Uberti <[email-masked]>
Date: Fri, 27 Sep 2013 10:43:02 -0700

> something like "When createOffer is called after the initial

Good catch. There are states between the initial state and the completion
of the o/a exchange, so the text probably needs to be more along the lines
of
"When createOffer is called a second (or later) time, or called after a
local or remote description has been installed..."

Will try to wordsmith this a bit.

> removed etc, with the only constraint being to not reuse dynamic

Certainly, this is possible, but we probably want this to only happen when
explicitly requested by JS. For example, if a track is put on hold, I don't
think we want to renegotiate all codecs at that time. Hence the current
text.

If we do provide APIs for this, this behavior change would be covered in
the Constraints Handling section.

> I prefer the hyphen too, since it better matches the o= line. Does anyone
feel strongly about this?