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

[Michael Welzl <[e-mail]>]

Hi,

I second that.

Here's one more reason: I believe that it should also be possible for a 
receiver to make use of retransmitted I-macroblocks from old frames that 
have been shown long ago. Future MBs may still depend on them, and so 
their quality could be improved with that information.

This is a quite theoretical idea - I don't have any proof that this 
would work, and don't know of research that has that proof (but I 
suspect one can find some, if one looks). It's just one more reason why 
retransmissions could turn out to be valuable.

Cheers,
Michael


On 6/28/12 9:49 AM, Magnus Westerlund wrote:
> 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)
>>
>>
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>