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Moving forward with SDP control

From: Harald Alvestrand <harald@alvestrand.no>
Date: Tue, 16 Jul 2013 14:17:57 +0200
Message-ID: <51E539F5.3010702@alvestrand.no>
To: "public-webrtc@w3.org" <public-webrtc@w3.org>
Hi all,

Recently there has been a lot of discussion (primarily in the 
IETF/rtcweb space though, but this topic really belongs here) about the 
desire to meet most use-cases without having to parse, modify or 
construct SDP.
This was discussed already as part of the discussion on whether 
PeerConnection and SDP should be maintained or not last year [1].

In the meantime, a number of API extensions have been created, notably 
the constraints setting and modification interfaces, which seem likely 
to be useful in achieving the goals people seek to achieve by SDP mangling.

However, this work has not progressed very quickly, or very comprehensively.
It may be time for a more structured approach.

We think it makes sense to divide the information needed into subcategories:

* Define the use cases for which SDP mangling is currently thought to be 
required - the "why" of the SDP tweaking.

* Propose what parameters one should be able to control/influence 
without having to do SDP mangling. A proposal should describe what the 
current API specification produces, what the needed mangling is, and 
what the desired effect of the mangling is - the "what" of the SDP tweaking.

* Propose suitable API surfaces to control/influence how media is 
encoded and transported over the network - the "how" of the SDP 
tweaking. We think that a requirement should be that working 
applications do not break when adding this surface - if it is not used 
things should work as today.

Someone may make a proposal encompassing all 3 pieces of information 
(why, what and how) - or just some of the first ones - or a proposal for 
a latter one that builds upon others' proposals (a "how" building on 
someone else's "why" and "what"). But we would not want to consider a 
"how" without a "what", or a "what" without a "why" - it just becomes 
impossible to figure out whether the original requirement is satisfied 
if we don't build all 3 layers of the proposals.

Does this sound like a way we could move forward?

Harald for the chairs.

[1] http://lists.w3.org/Archives/Public/public-webrtc/2012Sep/0098.html
Received on Tuesday, 16 July 2013 12:18:30 UTC

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