- From: Magnus Westerlund <magnus.westerlund@ericsson.com>
- Date: Tue, 12 Jul 2011 16:24:14 +0200
- To: Harald Alvestrand <harald@alvestrand.no>, public-webrtc@w3.org
On 2011-07-12 13:48, Harald Alvestrand wrote: > On 07/11/11 22:18, Magnus Westerlund wrote: >> >>> It's logical for these RTP sessions to be bidirectional. >> RTCP within an given RTP session should always be bi-directional for >> efficiency in number of transport flows needing to be established and >> NAT traversal. Some application usages will result in that some RTP >> session will only be unidirectional when it comes to actual media >> streams. And uni-directional media streams of different purposes should >> not be group together into a common RTP session over the same >> bi-directional transport just to create bi-directional flows as that >> messes with RTCP behavior. >> > To be clear about the word "purpose" here, since it's gotten me into > trouble several times: > > Sending two video streams from one sender (for instance a MUC) to one > recipient (for instance an user) counts as one "purpose", right? Even > though one may be a high-res document-sharing screencast and the other > is a thumbnail-appropriate talking head? I would say that document sharing and a view of the presenter are actually two different purposes. The reasons is that if one would have a central node performing switching operation on these streams, they would likely be different behaviors. If the usage scenario is that a group discusses a set of slides coming from one end-point. Then the slides should be distributed to all unconditionally. However, which speaker video stream to forward by the central unit is the one that is currently the most active speaker. Thus different behaviors. I use the word purpose, in the meaning the streams purpose in the application, but it might be easier to think of this as different application behavior around the streams. In the end it is the application needs and behaviors that truly will separate the streams into different type of sessions. > > While sending an audio stream and a video stream, even though they come > from the same source and are intended to be presented together, counts > as two different "purposes", right? To clarify in the case of two different media types, they always have different purposes/behaviors. Cheers Magnus Westerlund ---------------------------------------------------------------------- Multimedia Technologies, Ericsson Research EAB/TVM ---------------------------------------------------------------------- Ericsson AB | Phone +46 10 7148287 Färögatan 6 | Mobile +46 73 0949079 SE-164 80 Stockholm, Sweden| mailto: magnus.westerlund@ericsson.com ----------------------------------------------------------------------
Received on Tuesday, 12 July 2011 14:24:44 UTC