Re: [rtcweb] RTP Usage: Is RTP Retransmission REQUIRED or RECOMMENDED

["Roni Even" <[e-mail]>]

Hi Magnus,
So using retransmission is at the cost of losing lip synch which is very
noticeable. I am not saying that it does not work to do retransmission, my
claim that it is not practical and this is why I do not think it is
required.
Roni

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of
Magnus Westerlund
Sent: 28 June, 2012 9:49 AM
To: [e-mail]
Subject: Re: [rtcweb] RTP Usage: Is RTP Retransmission REQUIRED or
RECOMMENDED

Hi,

As Individual I like to state my position.

We have a video conference system developed by my colleagues used internally
at Ericsson that uses RTP Retransmission for video, not for audio with great
success. This is implemented such that we actually allow the video to fall
behind the audio when packet loss and retransmission is not able to repair
in a timely enough fashion. The benefit is minimal overhead and still no
loss induced degradations in the video. Yes, we get degradation in form of
frame display jittering and short freezes. But those events that are truly
visible are rare over wired networks.

I am personally convinced that RTP Retransmission is great tool in the
toolbox when it comes to improve media quality in many use cases. Yes there
are scenarios where RTP retransmission is less efficient. Long RTTs (over
200-400 ms) is the primary source of degradations. Compared to FEC it so
much more efficient from bandwidth consumption perspective.

I also think it is important that we have some mandatory to implement tool
for making the transport more robust now that we have a consensus that we
are not going for a FEC solution in the initial specification.

Thus my personal position is that RTP Retransmission should be REQUIRED to
implement.

Cheers

Magnus


On 2012-06-27 09:36, Magnus Westerlund wrote:
> WG,
> 
> We had a discussion at the interim if RTP Retransmission is to be 
> considered REQUIRED or RECOMMENDED to implement. I would like to see 
> if we can first have some discussion on this topic before moving on to 
> see if we can get a consensus here on the mailing list.
> 
> Please provide your views on this topic.
> 
> Cheers
> 
> Magnus Westerlund
> (As Chair and document editor)
> 
> 
> ----------------------------------------------------------------------
> Multimedia Technologies, Ericsson Research EAB/TVM
> ----------------------------------------------------------------------
> Ericsson AB                | Phone  [phone]
> Färögatan 6                | Mobile [phone]
> SE-164 80 Stockholm, Sweden| mailto: [e-mail]
> ----------------------------------------------------------------------
> 
> 
> _______________________________________________
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> 
> 


-- 

Magnus Westerlund

----------------------------------------------------------------------
Multimedia Technologies, Ericsson Research EAB/TVM
----------------------------------------------------------------------
Ericsson AB                | Phone  [phone]
Färögatan 6                | Mobile [phone]
SE-164 80 Stockholm, Sweden| mailto: [e-mail]
----------------------------------------------------------------------



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