CNAME and synchronization contexts

[aboba]

From: Emil Ivov emcho@jitsi.org
Date: Sat, 31 May 2014 10:25:55 +0200
To: "public-ortc@w3.org" public-ortc@w3.org
URL: http://lists.w3.org/Archives/Public/public-ortc/2014May/0142.html

We have been looking at recording WebRTC conferences lately and have
noticed how Chrome sends different CNAMEs for every media source.

CNAMEs have traditionally been used to determine whether two streams are
synchronise-able so having unique CNAMEs for an audio and a video flow
originating at the same host is kind of awkward.

Do we have a position on this for ORTC implementations? Should they be
encouraged to share CNAMEs within the same session (page). If not, then
should we provide a way for the page to control that?

[aboba]

Robin's response: http://lists.w3.org/Archives/Public/public-ortc/2014Jun/0010.html

[aboba]

Based on Emil's response, it would appear that developers can live without additional functionality:
http://lists.w3.org/Archives/Public/public-ortc/2014Jun/0020.html

[aboba]

Given that there does not appear to be an API requirement here, I am going to close this. If you feel that is wrong, please reopen and give your idea of the requirements.

[aboba]

From Robin:

So based on this, I suggest we add a “cname" property to the “parameters.rtcp” dictionary.

Developer could then override and force a cname on a sender/receiver:
parameter.rtcp.cname = “myvalue”;

and to learn the defaulted value, get the ‘parameters’ object to get the default value:
var cname = sender.getParameters().rtcp.cname;

Assuming others think the “rtcp” dictionary is the appropriate spot for getting/setting the cname...

[robin-raymond]

We need to define the behaviour in the specification for cname.

[aboba]

How about this for Section 9.6.1?

"cname of type DOMString

The Canonical Name (CNAME) used by RTCP (e.g. in SDES messages). Guidelines for CNAME generation are provided in [RTP-USAGE] Section 4.9. By default, ORTC implementations should set the CNAME to be the same within all RTCRtcpParameter objects created within the same Javascript sandbox. However, for backward compatibility with WebRTC 1.0, applications may set the cname to an alternative value."