Re: [AVT] Video streaming withour RTCP

If we are going to add some language, I'd like to make sure we make a
clear point that RTCP provides the only standard way to get
*visibility* into the playback behavior (ie, packet loss rate etc) at
the end points.  Even if you don't plan to actively *use* that data
for stream control, it's very important to have that data for some
applications - and RTCP provides the standard way to get it.  I have
to explain this constantly to folks - more specific language about
"Why RTCP?" would be a good thing.

Greg

On 4/2/07, Magnus Westerlund <magnus.westerlund@ericsson.com> wrote:
> Jaehwan Kim skrev:
> >
> >
> > Hi,
> >
> > And could you explain more in detail?
> >
> > I would appreciate if you give us an example.
> >
> >
> >
> > If there is a common misconception happening again and again, IMO, the
> > notion with enough examples should be into RTSP specification.
>
> Okay, we will log a request to clarify that RTP-Info only provides for
> initial sync and that RTCP is needed for maintaining sync in the case of
> clock drift. But there is much more on timestamp handling in
> http://tools.ietf.org/html/draft-ietf-mmusic-rfc2326bis-14
> than what is in RFC 2326.
>
> I could also recommend looking at the How To write RTP payload formats
> that has some discussion on the RTCP synch mechanism or Colin Perkins
> book on RTP.
> http://tools.ietf.org/html/draft-ietf-avt-rtp-howto-01
>
> There is also need to have RTCP for synch in cases such as multiple
> sources (SSRCs) and live sessions. In addition RTCP is needed for its
> transport monitoring purpose. The sender can't do any type of adaptation
> or avoid causing long term congestion unless RTCP is used.
>
> Cheers
>
> Magnus Westerlund
>
> IETF Transport Area Director & TSVWG Chair
> ----------------------------------------------------------------------
> Multimedia Technologies, Ericsson Research EAB/TVM/M
> ----------------------------------------------------------------------
> Ericsson AB                | Phone +46 8 4048287
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> _______________________________________________
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> avt@ietf.org
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>

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