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Re: [AVT] alignment of layers issue

I have the feeling, that you as well as Ross and unfortunately also others completely misunderstood the discussion we had up to now. No one ever said "do not use RTCP". RTCP must be used what it is built for, as for inter-session lip-sync. What we did was to raise the question, whether this also works under all possible circumstances (available clocks on today's PC systems) for sample-exact alignment of data between sessions. Making this to a discussion on "using or not using RTCP", does not make any sense and was absolutely not our intention.

Thomas

Ver Steeg, Bill wrote: 
Ross/Roni

I also believe that there are good reasons to implement the full RTP
suite, particularly for video flows. However, we are "preaching to the
choir" here. The readers of this list are a self selecting crowd. The
folks who do not use RTP for video flows do not read this list, and
probably do not attend the IETF.

It would be interesting to ask other SDOs (like CableLabs or W3C) to
comment on "the elephant in the room". It may even be more instructive
to ask implementers who operate outside of standards groups their
opinion on this matter. I am not sure how we solicit that data, though. 

I suspect that most applications programmers do not know that RTP
exists, much less understand its merits. In many cases, it is these
applications programmers that decide what encapsulation to use for their
data flows.

Bill VerSteeg

-----Original Message-----
From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] On Behalf Of
Roni Even
Sent: Thursday, November 20, 2008 4:45 PM
To: 'Ross Finlayson'; avt at ietf.org
Subject: Re: [AVT] alignment of layers issue

Ross,
I want to believe that this is not the case. At least for video codec
you need RTCP for other reasons as defined in RTCP feedback and the
extensions in the ccm draft.
Roni Even

-----Original Message-----
From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] On Behalf Of
Ross Finlayson
Sent: Wednesday, November 19, 2008 1:56 AM
To: avt at ietf.org
Subject: Re: [AVT] alignment of layers issue

At 2:53 PM -0600 11/18/08, Magnus Westerlund wrote:
  
 > Anyway, let us assume for the time being, we can make this work 
with a
    
 relatively complex implementation in the sender as well as in the
      
receiver.
  
This is not complex, it is standard RTCP that you anyway need to 
implement
    

It seems to me that there's "an elephant in the room" here.  I can't
help but feel that many (though not all) of the people who are opposing
adopting the standard RTCP SR-based solution are really doing so because
they don't want to implement RTCP.  I.e., they want to get away with
implementing only a restricted version of RTP that works just for one
particular layered video codec (and perhaps also one particular audio
codec for which they would also align timestamps), without RTCP at all.

If this is really true, then it would be useful if people would come
clean about this, so that we can address, or put to rest, whatever
fears/concerns they may have about implementing RTCP.

	Ross.
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Audio/Video Transport Working Group
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https://www.ietf.org/mailman/listinfo/avt



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