Subject: [rtcweb] #20: Section 12.2: Multiple Sources

From: "rtcweb issue tracker" <[email-masked]>
Date: Sat, 20 Apr 2013 01:56:37 -0000

#20: Section 12.2: Multiple Sources

 12.2.  Multiple Sources

    A WebRTC end-point might have multiple cameras, microphones or audio
    inputs and thus a single end-point can source multiple RTP media
    streams of the same media type concurrently.  Even if an end-point
    does not have multiple media sources of the same media type it has to
    support transmission using multiple SSRCs concurrently in the same
    RTP session.  This is due to the requirement on an WebRTC end-point
    to support multiple media types in one RTP session.  For example, one
    audio and one video source can result in the end-point sending with
    two different SSRCs in the same RTP session.  As multi-party
    conferences are supported, as discussed below in Section 12.3, a
    WebRTC end-point will need to be capable of receiving, decoding and
    play out multiple RTP media streams of the same type concurrently.

    tbd: Are any mechanism needed to signal limitations in the number of
    active SSRC that an end-point can handle?

 [BA] There are some additional nasty problems that come up here in the
 case where there are multiple sources that are each utilizing
 simulcast/layered coding. Among other things, there needs to be a way in
 RTP (not just SDP) to make it clear how the RTP streams relate. For
 example, imagine a mixer that is receiving simulcast/layered coding from
 multiple sources.  What set of SSRCs issue from that mixer, and what is
 contained in the SDES packet that lets a receiver know that the multiple
 SSRCs represent layered coding from a single source? I presume the SRCNAME
 document was one attempt at handling this problem, but since that didn't
 become a WG work item, we're still left with an unfilled need.  And no,
 this isn't handled in any of the GRUMBLE/FUMBLE/MUMBLE proposals.

-- 
-------------------------------------+-------------------------------------
 Reporter:                           |      Owner:  draft-ietf-rtcweb-rtp-
  [email-masked]          |  [email-masked]
     Type:  defect                   |     Status:  new
 Priority:  major                    |  Milestone:  milestone1
Component:  rtp-usage                |    Version:  1.0
 Severity:  Active WG Document       |   Keywords:
-------------------------------------+-------------------------------------

Ticket URL: <http://trac.tools.ietf.org/wg/rtcweb/trac/ticket/20>
rtcweb <http://tools.ietf.org/rtcweb/>