Subject: RE: [AVT] H.264 payload format and packet duplication

From: [email-masked]
Date: Fri, 22 Nov 2002 13:14:02 -0600

> 
> > As I mentioned in today's meeting there is reason why the 
> payload format
> > should not suggest to use packet replication:
> > - By replicating whole UDP/RTP/payload packets the RTCP 
> statistics does
> > not count the replicated packets. This prevents adaptation 
> mechanisms
> > relying on RTCP statistics to make the correct decision.
> > - Replication increase bandwidth and may cause congestion 
> and therefore
> > needs some type of congestion control.
> > So packet replication increase the need for congestion 
> control and at
> > the same time makes the statistics less correct.
> >
> > Therefore this notion should be removed and instead if the 
> functionality
> > is wanted, the draft should point to some type of FEC, for 
> example RFC
> > 2733 or rather a successor.
> 
> I agree, this is an important point.  Our congestion control mechanism
> depends upon accurately measuring loss.  If packets are replicated,
> the receiver can't do that.  This is essential.
> 
>                                                         -- Steve

This was also one of the basic assumption in the design of the retransmission payload format. If you want to achieve "packet duplication", you could use retransmission for streaming applications or FEC for more conversational type of applications.

David. 
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