Message-ID: <BLU169-W5F02AED8725E7A1D94E4D93970@phx.gbl>
Content-Type: multipart/alternative;
 boundary="_75c751b4-5f9b-4886-bca6-4dd4da63ba7c_"
From: Bernard Aboba <bernard_aboba@hotmail.com>
To: Colin Perkins <csp@csperkins.org>
Date: Mon, 27 May 2013 17:10:33 -0700
Importance: Normal
In-Reply-To: <DC56B228-927A-4ADB-B366-0CC739416CE2@csperkins.org>
References: <519E5F54.3000806@alum.mit.edu>
 <BLU403-EAS11291D50BCA39955DE3C9C393940@phx.gbl>
 <51A381E2.9040203@alum.mit.edu>,
 <DC56B228-927A-4ADB-B366-0CC739416CE2@csperkins.org>
MIME-Version: 1.0
Cc: IETF MMUSIC WG <mmusic@ietf.org>
Subject: Re: [MMUSIC] Associating packets with m-lines in a bundle
Precedence: list

--_75c751b4-5f9b-4886-bca6-4dd4da63ba7c_
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Colin Perkins said:=20

RTCP operates at a different level=2C so it's not clear why it needs to be =
bound to an m=3D line. Use the SSRC to group related RTP and RTCP packets a=
ccording to source=2C and match them to a de-jitter buffer and the state fo=
r RTCP processing. Use the PT to match those sources with the payload forma=
t=2C m=3D line and the corresponding decoding and rendering context.
[BA] I believe that the stats API requires the mapping of received RTCP pac=
kets to a peerConnection object.   Without BUNDLE=2C there is no issue.  Wi=
th BUNDLE and without a=3Dssrc lines=2C it is possible to receive RTCP RRs =
from SSRCs that have not yet sent packets=2C so that it wouldn't be possibl=
e yet to group the RTCP and RTP packets according to source and match those=
 sources with the PT and payload format.  So if you had more than one peerC=
onnection object=2C it might not be clear which object the RTCP packet rela=
ted to.=20
Colin also said:=20
Match the RTCP to the RTP based on the SSRC=2C and process it. There is no =
need to discard the RTCP in this case.
[BA] What if no RTP has been received from that SSRC=2C but an RTCP RR arri=
ves?  This is the case I was referring to.   I agree that there is no need =
to discard the RTCP assuming that an RTP packet from that SSRC arrives firs=
t=2C permitting a mapping of SSRC to PT=2C corresponding m line and peerCon=
nection object. 		 	   		  =

--_75c751b4-5f9b-4886-bca6-4dd4da63ba7c_
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<html>
<head>
<style><!--
.hmmessage P
{
margin:0px=3B
padding:0px
}
body.hmmessage
{
font-size: 12pt=3B
font-family:Calibri
}
--></style></head>
<body class=3D'hmmessage'><div dir=3D'ltr'>Colin Perkins said:&nbsp=3B<br><=
br><div>RTCP operates at a different level=2C so it's not clear why it need=
s to be bound to an m=3D line. Use the SSRC to group related RTP and RTCP p=
ackets according to source=2C and match them to a de-jitter buffer and the =
state for RTCP processing. Use the PT to match those sources with the paylo=
ad format=2C m=3D line and the corresponding decoding and rendering context=
.</div><div><br></div><div>[BA] I believe that the stats API requires the m=
apping of received RTCP packets to a peerConnection object. &nbsp=3B Withou=
t BUNDLE=2C there is no issue. &nbsp=3BWith BUNDLE and without a=3Dssrc lin=
es=2C it is possible to receive RTCP RRs from SSRCs that have not yet sent =
packets=2C so that it wouldn't be possible yet to group the RTCP and RTP pa=
ckets according to source and match those sources with the PT and payload f=
ormat. &nbsp=3BSo if you had more than one peerConnection object=2C it migh=
t not be clear which object the RTCP packet related to.&nbsp=3B</div><div><=
br></div><div>Colin also said:&nbsp=3B</div><div><br>Match the RTCP to the =
RTP based on the SSRC=2C and process it. There is no need to discard the RT=
CP in this case.</div><div><br></div><div>[BA] What if no RTP has been rece=
ived from that SSRC=2C but an RTCP RR arrives? &nbsp=3BThis is the case I w=
as referring to. &nbsp=3B I agree that there is no need to discard the RTCP=
 assuming that an RTP packet from that SSRC arrives first=2C permitting a m=
apping of SSRC to PT=2C corresponding m line and peerConnection object.</di=
v> 		 	   		  </div></body>
</html>=

--_75c751b4-5f9b-4886-bca6-4dd4da63ba7c_--