Re: [splices] Using Two Separate Devices to Start a Conversation proposal

Paul Kyzivat <pkyzivat@cisco.com> Mon, 06 June 2011 23:45 UTC

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Date: Mon, 06 Jun 2011 19:45:49 -0400
From: Paul Kyzivat <pkyzivat@cisco.com>
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Subject: Re: [splices] Using Two Separate Devices to Start a Conversation proposal
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I suspect asymmetric rtp *won't* work a lot of the time, for many 
reasons, whether we think they are reasonable or not.

Maybe this is just an unreasonable use case. I can't really imagine 
wanting to do this. If I have a handset, or headset, with a mic, it 
probably has a "speaker" too, and it would seem weird using the mic and 
not its speaker too. And when they are separate there is likely to be 
problems with echos.

	Thanks,
	Paul

On 6/6/2011 7:27 PM, Peter Musgrave wrote:
> Hi all,
>
> My assumptions were that:
> - Alice's desk phone is doing the media aggregation and creating a
> reINVITE for Bob with a=sendrecv and asymmetric media:
>    * media is sent from Bob to Alice desk phone
>    * media is sent from Alice Computer to Bob
>
> As far as Bob knows this is a dialog only with Alice's deskphone. Bob
> does not have to support SPLICES or do anything special.
>
> Bob must handle asymmetric RTP from Alice.
>
> Ok?
>
> I agree that requiring media relay does become a bad idea when the
> relaying element is e.g a cellphone.
>
> Do we think that having asymmetric RTP will be ok? A lot of
> implementation have worked toward symmetric RTP (and some will only play
> RTP arriving from the place they are sending to! [1 implementation at
> SIPIT28, 3 at SIPIT27 - so maybe not worth worrying about]). Are there
> any issues with ZRTP or use of ICE? [I am not an ICE expert so I can't
> recall if symmetric RTP was baked into ICE, umm "frozen in" to ICE maybe?]
>
> Regards,
>
> Peter
>
>
>
>
>
> On Mon, Jun 6, 2011 at 5:45 PM, Alan Johnston <alan.b.johnston@gmail.com
> <mailto:alan.b.johnston@gmail.com>> wrote:
>
>     But isn't the INVITE Join received at Alice's Desk Phone?  If so, then
>     a normal Join will result in Alice's Desk Phone performing mixing of
>     audio streams from Alice's PC, Alice's Desk Phone, and Bob.  I thought
>     what was desired (and shown by Rifaat's flow) was that Alice's Desk
>     phone did not mix the media, but instead inserted/spliced the media
>     from Alice's PC into the dialog with Bob, resulting in a re-INVITE to
>     Bob with two m= lines.
>
>     - Alan -
>
>     On Mon, Jun 6, 2011 at 4:15 PM, Worley, Dale R (Dale)
>     <dworley@avaya.com <mailto:dworley@avaya.com>> wrote:
>      > No, surely it is an ordinary join.  At the far UA, there are two
>     incoming dialogs, each with one audio m= line.  The only oddity is
>     that one dialog is recvonly (at the far UA), and so is never sent
>     media.  The other dialog is sendonly (at the far UA) and so never
>     provides audio to the mixing, but is only sent the result of the
>     mixing.  The effect is that the far UA's input audio is sent only to
>     the second dialog, and the far UA's output audio is driven only by
>     the first dialog.
>      >
>      > Dale
>      >
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